A. Cruise Narrative: A01 and A02 A.1. Highlights WHP Cruise Summary Information WOCE section designation A01 | A02 Expedition designation 06MT30_3 | 06MT30_2 Chief Scientist(s)/affiliation Jens Meincke/IfMHH | Peter Koltermann/BSH Dates 1994.11.15-1994.12.19 | 1994.10.12-1994.11.12 Number of stations 63 | 53 Floats and drifters deployed 6 Floats deployed | 0 floats deployed Moorings deployed or recovered 0 | 0 Ship RV METEOR Ports of call Hamburg to St. John's to Hamburg Geographic boundaries A01 60°33.90'N 54°29.50'W 14°15.40'W 51°35.10'N A02 49°14.10'N 48°45.00'W 10°39.60'W 41°59.60'N Contributing Authors, (as they appear in text) W. Balzer B. Owens K. Jeskulke R. Kramer O. Pfannkuche I. Büns T. Soltwedel F. Oestereich H. Thiel A. Pfeifer K.C. Soetje D.S. Kirkwood B.v. Bodungen A. Deeken V. Terechtchenkov E. Gier U. Brockmann H. Dierssen P. Wöckel F. Müller M. Andreae S. Otto M. Stolley P. Heil K.P. Koltermann H. Wellmann H. Johannsen A. Schaub J. Duinker G. Uher F. Malien C. Atwood L. Mintrop O. Flöck A. Putzka A. Krötzinger W. Roether G. Schebeske K. Bulsiewicz S. Schweinsberg J. Meincke V. Ulshöfer C. Rüth A.v. Hippel R. Bayer A.N Antia H. Rose C. Senet A. Sy W. Erasmi B. Kromer H. Thomas M. Rhein R.S. Lampitt M. Born R. Prado-Fiedler B. Schneider T. Kumbier D. Kirkwood G.M. Raisbeck G. Lehnert I. Horn R. Davis K. Poremba METEOR CRUISE M30 JGOFS, OMEX and WOCE in the North Atlantic 1994 Cruise No 30 7 September - 22 December 1994 Las Palmas - Hamburg - St John's - Hamburg TABLE OF CONTENTS ABSTRACT ZUSAMMENFASSUNG 1 RESEARCH OBJECTIVES Leg M30/1: Las Palmas - Hamburg OMEX Ocean Margin Exchange Legs M30/2-3: Hamburg - St. John's - Hamburg WOCE World Ocean Circulation Experiment JGOFS Joint Global Ocean Flux Study 2 PARTICIPANTS 2.1 Leg M30/1 2.2 Leg M30/2 2.3 Leg M30/3 2.4 Participating Institutions 3 RESEARCH PROGRAMMES 3.1 OMEX Programmes: 3.1.1 Organic Matter Degradation, Denitrification and Trace Metal Diagenesis 3.1.2 Carbon Mineralization by the Benthic Community 3.1.3 Vertical Particle Flux at the Continental Margin 3.1.4 Phase Transfer of Organic Compounds During Shelf Edge Passage 3.1.5 Flux of Trace Gases at the Boundary Between Ocean and Atmosphere 3.2 WOCE Programmes: 3.2.1 Determination of the Meridional Transports of Heat, Salt and Freshwater at 48°N in the North Atlantic along the WHP section A2 3.2.2 Nutrients Measurements for the Fine Resolution of Oceanic Water Masses on the Meteor Cruise M30/2 (section WHP-A2) in the North Atlantic 3.2.3 CFCs on the section WHP-A2 3.2.4 Mooring Recovery on sections WHP-A2 and WHP-A1 3.2.5 Tritium/Helium and 14C-Sampling along WHP-sections A2 and A1 3.2.6 WOCE North Atlantic Overturning Rate Determination (WOCE-NORD, WHP section A1) 3.2.7 CFCs on the section WHP-A1 3.3 JGOFS - Programmes: 3.3.1 The Control Function of the Carbonate-System in the Oceanic CO2 uptake, WHP-A2 3.3.2 The Ocean as a CO2 Sink: Complimentary Studies of the Baltic Sea and the North Atlantic, WHP-A1 3.4 Individual Projects 3.4.1 129I from Nuclear Fuel Processing as an Oceanographic Tracer 3.4.2 Profiling ALACE Floats to Determine the Development of the Stratification in the Labrador Sea Over Two Years 4 NARRATIVE OF THE CRUISE 4.1 Leg M30/1 (Chief Scientist-O. Pfannkuche) 4.2 Leg M30/2 (Chief Scientist-K.P. Koltermann) 4.3 Leg M30/3 (Chief Scientist-J. Meincke) 5 OPERATIONAL DETAILS AND PRELIMINARY RESULTS 5.1 OMEX Programmes: 5.1.1 Biochemistry - Phase Transfer of Organic Compounds During Shelf Edge Passage - Organic Matter Degradation, Denitrification and Trace Metal Diagenesis - Dissolved Organic Carbon - Pore Water Chemistry - Benthis Denitrification and Bioirrigation 5.1.2 Air Chemistry - Exchange of Reduced Sulphur Compounds Between Ocean and Atmosphere 5.1.3 Sedimentology - Particle Flux and in situ Marine Aggregate Studies at the Continental Margin - Particle Flux - Marine Snow Studies - CTD - work 5.1.4 Benthic Biology - Benthic Microbiology - Carbon Mineralization by the Benthic Community 5.2 WOCE Programmes: 5.2.1 Physical and Chemical Oceanography on Leg M30/2 - Determination of the Meridional Transports of Heat, Salt and Freshwater at 48°N in the North Atlantic Along the WHP section A2 - Nutrients Measurements for Fine Resolution of Oceanic Water Masses on the Meteor Cruise M30/2 (section WHP-A2) in the North Atlantic - CFCs on the WHP section A2 - Tritium/Helium and 14C-Sampling Along WHP-sections A2 and A1 5.2.2 Mooring Recovery on WHP-A2 and WHP-A1 5.2.3 Physical, Chemical and Tracer Oceanography on Leg M30/3 - Hydrographic Measurements on WHP-A1 Nutrients Along WHP-A1 - Spreading of Newly Formed Labrador Sea Water - Thermosalinograph, XBT and XCTD Measurements XBT Sections XCTD Field Test - Sample Oxygen Measurements on WHP-A1 - Nutrient Measurements on WHP-A1 - Tracer Studies on WHP-A1 Tracer Oceanography: Tritium/Helium and Radiocarbon Tracer Oceanography: CFCs 5.3 JGOFS Programmes: 5.3.1 The Control Function of the Carbonate-System in the Oceanic CO2 uptake, WHP-A2 5.3.2 The Ocean as a CO2 Sink: Complimentary Studies of the Baltic Sea and the North Atlantic, WHP-A1 5.4 Individual Programmes: 5.4.1 129I from Nuclear Fuel Processing as an Oceanographic Tracer 5.4.2 ALACE Float Deployments 6 SHIP'S METEOROLOGICAL STATION 6.1 Leg M30/1 6.2 Leg M30/2 6.3 Leg M30/3 7 LISTS 7.1 List of Stations 7.1.1 Lists of Sampling Stations M30/1 7.1.2 Station List Leg M30/2 Section WHP-A2 - Summary of Sub-Sampling Schemes, Hydrographic Stations on M30/2 - Summary of Daily Station Activities M30/2 7.1.3 Station List Leg M30/3 Section A1W - Station List Leg M30/3 Section A1E 7.2 List of Moored Instruments 7.2.1 Leg M30/1 Sediment Trap Mooring Positions 7.2.2 Leg M30/2 Current Meter Mooring Positions 7.2.3 Leg M30/3 Current Meter Mooring Positions 7.3 List of Figures 8 CONCLUDING REMARKS 9 REFERENCES 10 NOTES ABSTRACT The Meteor Cruise M30 focused on the North Atlantic components of the global research programmes Joint Ocean Flux Study JGOFS, the World Ocean Circulation Experiment WOCE and the European programme Ocean Margin EXchange OMEX. On the first leg, the exchange processes between the oceanic continental margins and the open ocean were addressed. A special emphasis has been put in this programme on the interfaces sediment/ocean and ocean/atmosphere. The Celtic shelf edge was chosen as the regional focus for this multidisciplinary research work. The second and third leg used the unique opportunity to determine the modification and partitioning of the North Atlantic water masses in a fully enclosed region between 48( and 61(N. This programme is part of a longer-lasting effort to observe long-term changes of the meridional transports of heat, salt and fresh-water on time scales relevant to climate change. The WOCE component of ca. 10 weeks field- work will be used to describe in space the quasi-synoptic evolution of the hydrographic situation of the "overturning cell" of the global thermohaline circulation in the North Atlantic Ocean. Previous assessments as part of the WOCE Hydrographic Programme WHP on the section WHP-A1E in 1991 by FS Meteor, of AR7E in September 1992 with FS Valdivia (WOCE-NORD) and of WHP-AR19 in summer 1993 with FS Gauss already showed dramatic changes in water mass properties and the depth of individual water mass layers compared to work done during the International Geophysical Year IGY in 1957 and other in 1962 and 1982. These changes in intermediate and deep water masses associate directly with the annual winter sections worked in the Labrador Sea by Canadian colleagues since 1988 and this new assessment promises to describe in much greater details the linkage between local forcing and the large-scale reaction of the North Atlantic circulation. ZUSAMMENFASSUNG Die Meteor - Reise 30 war den nordatlantischen Komponenten der globalen Forschungsprogramme Joint Global Ocean Flux Study JGOFS und World Ocean Circulation Experiment WOCE und dem europäischen Programm Ocean Margin EXchange OMEX gewidmet. Im ersten Fahrtabschnitt (M30/1) standen die Austauschprozesse zwischen den ozeanischen Kontinentalrändern und dem offenen Ozean im Mittelpunkt. Dabei wurde ein besonderes Gewicht auf die Grenzflächen Sediment/Wasser und Ozean/Atmosphäre gelegt. Als regionaler Schwerpunkt für diese umfangreichen multidisziplinären Untersuchungen wurde der keltische Schelfrand gewählt. Der zweite und dritte Fahrtabschnitt (M30/2 und M30/3) boten die erstmalige Möglichkeit, die Modifikation der nordatlantischen Wassermassen und ihre daran beteiligten jeweiligen Anteile in einem abgeschlossenen Gebiet zwischen 48(N und 61(N eindeutig zu bestimmen. Diese Arbeiten führen die Beobachtung der langzeitigen klimarelevanten Schwankungen von meridionalen Wärme-, Salz- und Süßwassertransporten der letzten Jahre fort. Dabei gewährleistete das WOCE- Feldprogramm von ca. 10 Wochen erstmalig eine räumlich abgeschlossene quasi- synoptische Erfassung des hydrographischen Zustandes der "overturning cell" der globalen thermohalinen Zirkulation im Nordatlantik. Die bisherigen Aufnahmen im Rahmen des WOCE Hydrographic Programme WHP von WHP-A1E im Jahre 1991 mit FS "Meteor" bzw. von AR7E im September 1992 mit FS "Valdivia" (WOCE-NORD) und WHP- AR19 im Sommer 1993 mit FS "Gauss" haben bereits drastische Veränderungen in den Eigenschaften der Wassermassen und der Tiefe der individuellen Schichten der Wassermassen im Vergleich zu den früheren Aufnahmen während des Internationalen Geophysikalischen Jahr 1957 und in den Jahren 1962 und 1982 ergeben. Die erneute Erfassung der intermediären und tiefen Zirkulation insbesondere im Zusammenhang mit den jährlichen winterlichen Aufnahmen der Labrador-See durch kanadische Kollegen seit 1988 verbessert die Beschreibung der sich abzeichnenden Beziehung zwischen dem örtlichen "forcing" und der großräumigen Reaktion des nördlichen Atlantiks. 1 RESEARCH OBJECTIVES Leg M30/1: Las Palmas - Hamburg OMEX Ocean Margin Exchange On the first leg of METEOR cruise 30 the exchange processes of carbon and "green house" gases between the western European shelf edge and the open ocean were studied within the frame of an interdisciplinary European Union Programme "Ocean Margin Exchange" (OMEX). Station work concentrated on a transect from the outer Celtic Sea (Great Sole Bank) across the Goban Spur into the Porcupine Seabight covering a depth range from 220 m to 4800 m (Fig. 1). Special emphasis was put on the interfaces sediment/ocean and ocean/atmosphere. Legs M30/2 and M30/3: Hamburg - St. John's - Hamburg WOCE World Ocean Circulation Experiment This German contribution to the international WOCE Programme as part of the World Climate Research Programme WCRP focused on the Northern North Atlantic in late autumn. Here we find significant changes in the water mass characteristics such as temperature, salinity and the contents of dissolved oxygen caused by the highly variable meteorological forcing on annual and interannual time scales. These changes affect the contribution of the North Atlantic to the global thermohaline circulation in the form of the North Atlantic Deep Water and its signatures. It, in the end, will affect the meridional transports of heat, salinity and freshwater. For a highly resolved description of the water masses that are modified by these processes besides measurements of temperature and salinity, the concentrations of dissolved oxygen content, nutrients and a sequence of transient tracers such as CFCs, carbon 14C, helium 3He and 4He and tritium 3H was analysed from water samples. Using the characteristic input functions into the ocean, the relevant modification processes and their regions will be better resolved. Since the scientific programme for both cruise legs M30/2 and M30/3 is essentially identical and only most of the participating groups changed, for both legs a joint programme description is given below. The German contributions to WOCE and JGOFS have been funded by the Federal Ministry for Research and Technology (BMFT). JGOFS Joint Global Ocean Flux Study In co-operation with JGOFS, all WOCE WHP-sections are to be sampled for dissolved and particular CO2 to better quantify the ocean's role as a reservoir in the global carbon system. Sections A2 at 48(N and A1 at ca. 57(N have been sampled in this context. The data are being made available to the appropriate data centres. 2 PARTICIPANTS 2.1 Leg M30/1 NAME SPECIALITY INSTITUTION Pfannkuche, Olaf, Dr., Benthic Biology GEOMAR Chief Scientist Antia, Avan, Dr. Planktology IfMK Balzer, Wolfgang Prof. Dr. Marine Chemistry UBMCh Bassek, Dieter Weather Technician DWD/SWA Behrens, Katrin Benthic Biology IHF Bosse, Kai Benthic Biology IHF Büns, Ilse Biochemistry UHIBL Deeken, Aloys Marine Chemistry UBMCh Dierßen, Holger Marine Chemistry UBMCh Dölle, Martina Benthic Biology IHF Erasmi, Wolfgang Hydrography IfMK Flöck, Otmar Biogeochemistry MPICh Götz, Sabine Benthic Biology IHF Jeskulke, Karen Benthic Biology IfMK Kahl, G. Meteorology DWD/SWA Kumbier, Thomas Electronics IfMK Lampitt, Richard Dr. Planktology IOSDL Lehnert, Gerhard Planktology IOW Nuppenau, Volker Electronics IHF Otto, Sabine Marine Chemistry UBMCh Pfeiffer, Alexander Biochemistry UHIBL Poremba, Knut, Dr. Benthic Biology IfMK Schebeske, Günther Biogeochemistry MPICh Soltwedel, Thomas Dr. Benthic Biology IHF Uher, Günther Biogeochemistry MPICh Ulshöver, Veit Biogeochemistry MPICh Wellmann, Hartwig Marine Chemistry UBMCh Witte, Ursula Dr. Benthic Biology IHF 2.2 Leg M30/2 NAME SPECIALITY INSTITUTION Dr.Koltermann,Klaus Peter, Phys. Oceanography BSH Chief Scientist Wöckel, Peter CTD-support BSH Soetje, Kai C CTD-Computing BSH Mauritz, Heiko CTD-computing BSH Stolley, Martin Hydro watch BSH Frohse, Alex Salinometer BSH Berger, Ralf CTD-support IfMK Dr.Terechtchenkov,Vladimir Hydro watch BSH/PPS Hatten, Helge Hydro watch IfMHH Outzen, Olaf Hydro watch IfMHH Löwe; Peter Hydro watch BSH Giese, Holger Hydro/moorings BSH Dr. Mintrop, Ludger Chemistry/CO2 IfMK Körtzinger, Arne Chemistry/CO2 IfMK Johannsen, Helge Chemistry/nutrients IfMK Malien, Frank Chemistry/nutrients IfMK Schweinsberg, Susanne Chemistry/CO2 IfMK Senet, Christian Chemistry/CO2 IfMK von Hippel, Annette Chemistry/CO2 IfMK Atwood, Chris Chemistry/CO2 SIO Bulsiewicz, Klaus CFCs IUP-B Rose, Henning CFCs IUP-B Rüth, Christine CFCs IUP-B Dr. Bayer, Reinhold Tracer IUP-HD Dr. Kromer, Bernd Tracer IUP-HD Dr. Born, Matthias Tracer IUP-HD Rübel, André Tracer IUP-HD Kühr, Sabine Tracer IUP-HD Dr. Röd, Erhard Ship's Meteorologist SWA Lambert, Hans-Peter Weather Technician SWA 2.3 Leg M30/3 NAME SPECIALITY INSTITUTION Dr. Meincke, Jens, Phys Oceanography IfMHH Chief Scientist Dr. Sy, Alexander Hydrography BSH Bersch, Manfred Hydro watch IfMHH Paul, Uwe Hydro watch BSH Dr. Lazier, John Hydro watch BIO Gerdes, Jürgen Hydro watch IfMHH Haak, Helmuth Hydro watch IfMHH Bock, Jan Hydro watch IfMHH Dombrowski, Uwe CTD-support IfMK Verch, Norbert Salinometer IfMHH Mauritz, Heiko CTD-computing BSH Gottschalk, Ilse CTD-computing BSH Kramer, Rita O2 BSH Horn, Ines O2 BSH Oestereich, Frank O2/nutrients BSH Kirkland, Donald Nutrients MAFF Dr. Schneider, Bernd CO2 IOW Thomas, Helmut CO2 IOW Prado-Fiedler, Ronaldo CO2 IOW Dr. Bayer, Reinhold Tracer IUP-HD Dr. Born, Matthias Tracer IUP-HD Müller, Franziska Tracer IUP-HD Gier, Eva-Maria Tracer IUP-HD Dr. Rhein, Monika CFCs IfMK Haie, Petra CFCs IfMK Badewien, Thomas CFCs IfMK Dr Röd, Erhard Ship's Meteorologist SWA Lambert, Hans-Peter Weather Technician SWA 2.4 PARTICIPATING INSTITUTIONS BIO Bedford Institute of Oceanography, P.O.B. 1006, Dartmouth, N.S., B2Y 4A2, Canada BSH Bundesamt für Seeschiffahrt u. Hydrographie, Bernhard-Nocht-Str. 78, 20597 Hamburg, Germany CSNSM Centre des Spectrométrie Nucléaire et de Spectrométrie de Masse (IN2P3-CRNS), Bâtiment 108, 91405 CAMPUS ORSAY, France DWD Deutscher Wetterdienst, Seewetteramt, Bernhard - Nocht - Str. 76, 29359 Hamburg, Germany Geomar Forschungszentrum für marine Geowissenschaften der Christian-Albrechts- Universität zu Kiel, Wischhofstr. 1-3, 24148 Kiel, Germany IfMHH Institut für Meereskunde der Universität Hamburg, Troplowitzstr. 7, 22529 Hamburg, Germany IfMK Institut für Meereskunde an der Universität Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany IHF Institut für Hydrobiologie und Fischereiwissenschaft, Universität Hamburg, Zeiseweg 9, 22765 Hamburg, Germany IOSDL Institute of Oceanographic Sciences, Deacon Laboratory, Wormley, Godalming, Surrey GU8 5UB, United Kingdom now: Southampton Oceanography Centre, Empress Dock, Southampton, Hampshire, SO14 3ZH, United Kingdom IOW Institut für Ostseeforschung, Seestr. 15, 18119 Rostock-Warnemünde, Germany IUP-B Universität Bremen, Fachbereich 1, Institut für Umweltphysik, Abt. Tracer - Ozeanographie, Bibliotheksstrasse, 28359 Bremen, Germany IUP-HD Institut für Umweltphysik der Universität Heidelberg, Im Neuenheimer Feld 366, 69120 Heidelberg, Germany MAFF Ministry of Agriculture, Food and Fisheries, Fisheries Laboratory, Lowestoft, Suffolk NR33 0HT, United Kingdom MPICh Max-Planck-Institut für Chemie, Abt. Biogeochemie, Postfach 3060, 55020 Mainz, Germany UBMCh FB-2 Meereschemie, Universität Bremen, Postfach 330440, 28334 Bremen, Germany UHIBL Institut für Biochemie, Universität Hamburg, Martin-Luther-King Pl. 6, 20146 Hamburg, Germany IORAS/PPS P.P. Shirshov Institute of Oceanology, 23 Krasikova str., Moscow 117851, Russia SIO Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093, USA WHOI Woods Hole Oceanographic Institution, Woods Hole, Ma 02543, USA 3 RESEARCH PROGRAMMES 3.1 OMEX PROGRAMMES The OMEX project is funded by the European Union within the frame-work of MAST II ("Targeted Projects"). The various multinational and interdisciplinary programmes focus on the exchange processes of carbon and a variety of gases - which occur to be relevant to climatic changes - between European shelf areas, the adjacent continental margin and open ocean. Special emphasis is paid on exchange processes at the sediment/water and ocean/atmosphere interfaces. The Celtic Margin at the Goban Spur (Fig. 1), where leg M30/1 took place, was chosen as a regional focus of the OMEX project for the time span 1993-1995. The cruise M30/1 was part of a series of cruises of various European research vessels organized to gain a seasonal coverage of the sampling stations on the Goban Spur Transect. It was intended to investigate a typical autumn situation for the different processes. 3.1.1 ORGANIC MATTER DEGRADATION, DENITRIFICATION AND TRACE METAL DIAGENESIS (UBMCh, W. Balzer) For the understanding of the major controls over release fluxes from margin sediments a detailed investigation of early diagenetic processes acting within the sediments is necessary. Therefore, extensive work on pore water chemistry and on solid sediment phases at transects across the continental margin was conducted. The integrated rate of organic matter remineralization in near- surface sediments will quantified by modelling the pore water profiles obtained during M27. In dependence on both the diagenetic redox milieu and the input terms, the benthic reactions and fluxes of selected trace metals were investigated to assess the significance of margin processes for the trace metal chemistry of the ocean. By analysing the trace metal content in trapped particles, in suspended material, in sediments and in pore waters we will contribute to finding relationships between vertical/lateral sedimentation fluxes, benthic release fluxes and burial rates of chemically differing elements. A special study deals with sedimentary denitrification in continental margin sediments. 3.1.2 CARBON MINERALIZATION BY THE BENTHIC COMMUNITY (GEOMAR, O. Pfannkuche; IHF, H. Thiel) Rates of remineralization of organic carbon in the benthal are controlled by all transport processes in the water column. Parametrization of benthic processes is necessary to determine what portion of the sedimenting carbon is remineralized and what portion is accumulating in the sediments. The understanding of the biological, chemical and physical processes involved and their quantitative determination is vital for balancing carbon fluxes in the sediment. For the assessment of the role of benthic organisms for carbon cycling it is necessary to determine benthic community respiration, biomass production and benthic activity. Present knowledge obtained from deep-sea investigations of the temperate Atlantic Ocean suggests that benthic respiration, activity and biomass production is subject to strong seasonal variations which correlate with carbon input by sedimentation. The largest part of benthic carbon removal is by organism respiration, its seasonal range being 80-90%. The determination of in-situ benthic oxygen respiration rates by use of "bottom landers" is therefore of central significance for balancing the carbon fluxes. Since most of the biotic oxygen consumption is performed by micro- organisms, it is necessary to determine the part played by micro-organisms in community respiration and biomass production. The main objective of this project is the quantification of biological mediated carbon fluxes through the sediment measuring benthic oxygen consumption rates, metabolic activity and biomass production on a seasonal scale. 3.1.3 VERTICAL PARTICLE FLUX AT THE CONTINENTAL MARGIN (IfMK, B. v. Bodungen) The overall goal is the investigation of the seasonal pattern of particle sedimentation from the epipelagic zone to the sea floor and its dependence on the water depth at transects from the shelf edge to the abyssal plain. It is intended to identify the quality and relative significance of the different source materials. Therefore, the particle flux at different water depths were determined with high temporal resolution by using sediment traps. In the sedimenting material the following components and parameters have been determined: carrier phases, 15N/14N isotopic ratios, pigments, stable carbon isotopes, and trace elements. Light and electron microscopy was used to identify individual particles. In relation to the particulate fluxes of carbon and nitrogen as measured with traps, DOC- and DON-measurements of water samples serve to assess the significance of dissolved organic components for the cycling of carbon and nitrogen. 3.1.4 PHASE TRANSFER OF ORGANIC COMPOUNDS DURING SHELF EDGE PASSAGE (UHIBL, Uwe Brockmann) At the shelf edge, nutrient rich water masses are injected into the euphotic zone due to upwelling processes. Here, inorganic components are rapidly transformed into particulate organic material, a part of which sediments to the sea floor where it is subject to remineralization. The spatial distribution of these processes depends to a large extent on advective processes at the shelf edge. Provided that currents are directed consistently to the shelf edge, the succession of individual processes can be traced by analysing the distribution of nutrients as well as the distribution of the dissolved and particulate organic components. Because the different nutrient elements are remineralized at different rates, gross inferences on the state of the biological development may be drawn from measured element ratios in both the dissolved nutrients and in the dissolved/particulate organic substances. These investigations are closely related to hydrographic studies and to an ecosystem analysis at the shelf edge of the selected region. 3.1.5 FLUX OF TRACE GASES AT THE BOUNDARY BETWEEN OCEAN AND ATMOSPHERE (MPICh, M. Andreae) In collaboration with other European research groups the biogeochemical processes were investigated that are involved in the production and emission of trace gases being selected according to their relevance for climate and atmospheric chemistry. In continuation of measurements during the METEOR cruise M21/2 the photochemical production of carbonyl sulphide (COS) in the ocean and its exchange flux between ocean and atmosphere was determined. COS is produced from certain dissolved organic compounds and may be emitted to the atmosphere. Due to its long life time of more than one year, COS may reach the stratosphere where it forms the main source of the sulphate layer which influences both the ozone layer and the incoming solar radiation. Of particular significance in this context is the seasonal and spatial variability of the ocean as a source of COS. During M27/1 a photochemical/kinetic model was tested and now improved that considers light dependent production of COS, hydrolysis of COS and its exchange at the ocean/atmosphere interface as well as vertical mixing in the ocean. 3.2 WOCE PROGRAMMES: 3.2.1 DETERMINATION OF THE MERIDIONAL TRANSPORTS OF HEAT, SALT AND FRESHWATER AT 48°N IN THE NORTH ATLANTIC ALONG THE WHP SECTION A2 (BSH, K.P. Koltermann) The meridional transports of heat, freshwater and salt in the Atlantic Ocean and their seasonal and interannual changes are determined for the 90s across the latitude of the global maximum freshwater transport at ca. 50°N in the Atlantic Ocean. These results are compared with previous measurements in the 50s and 80s. This "time series" is augmented with Russian data along 48°N that have been collected at quarterly intervals between 1975 and 1987 down to a depth of 2000 m. This will result in a climatology of the changes in the surface and intermediate layers and will improve the estimate of the seasonal cycle. Comparisons with results from eddy-resolving modelling efforts are separately pursued. These estimates will provide the variance of these integral parameters, and finally lead to a history of their development since the IGY in 1957. This section elucidates the interaction of the thermohaline North Atlantic circulation with the wind-driven one at intermediate and great depths. Furthermore we expect a better formulation of the coupling between these changes and the changes in the "forcing fields", particularly the fluxes of latent and sensible heat, evaporation and precipitation E-P and wind stress from operational atmospheric models (ECMWF, NMC) at the surface. The WOCE-NORD project will in addition document estimates of the temperature distribution and heat content at ca. 50°N for the top kilometre on time scales of months from its VOS subprogramme to establish their seasonal cycle. In co-operation, we will attempt to complement the circulation estimates of the convective area north of 48°N with the estimates from this section. Working this section in the summer of 1993 with FS Gauss has shown the Labrador Sea Water temperatures some 0.4°C below its historical characteristic temperature, and deeper in the water column by some 700 m. This fits in with observations from the early 90s along 60°N and 24°30'N and indicates a rapid reaction of the intermediate circulation of the northern North Atlantic to changes in the forcing in the Labrador Sea. We expect to get some first estimates on how changes in the heat, salt and freshwater transports of the boundary currents of the North Atlantic continue into the ocean interior, and what likely impact this will have on the coupled ocean-atmosphere system. 3.2.2 NUTRIENTS MEASUREMENTS FOR THE FINE RESOLUTION OF OCEANIC WATER MASSES ON THE METEOR CRUISE M30/2 (SECTION WHP-A2) IN THE NORTH ATLANTIC (IfMK, J. Duinker, L. Mintrop) The concentrations of nutrients PO4, NO3, NO2, NH4, Si(OH)4 from 1692 samples and the content of dissolved oxygen O2 from 1737 water samples have been determined on board according to the WHP Standards. For quality assurance purposes additional samples were taken as duplicates or replicates. All data were processed on board, subjected to detailed consistency and quality checks and compared to existing data sets from this region. An annotated data file was produced at the end of the cruise, containing all relevant information and documentation on methodology and the quality of the data. 3.2.3 CFCS ON THE SECTION WHP-A2 (IUP-B, W. Roether) On all stations of the WOCE WHP section A2 water samples from all depths were analysed for CFCs. Some 1100 measurements of F11, F12, F113 and CCl4 have been processed. These data will be used to determine mixing rates and apparent ages of the water masses in the North Atlantic. Sampling and interpretation will be done in close co-operation with all groups involved. For running the CFC analyses onboard (1) 1062 samples for CFC have been collected and analysed for F11, F12, F113, CCl4. All analyses have been evaluated preliminarily at sea. (2) In addition 77 3He-samples have been collected (classical method) for inter comparisons with the Heidelberg group. All samples were collected with the standard rosette system. The CFC-samples were drawn on large glass syringes. During sampling, contamination with helium and CFCs was to be avoided or controlled. The sampling strategy on the section followed the WOCE recommendations. Except for shallower areas each station was sampled at up to 36 levels. The vertical resolution had a higher priority than the horizontal one for the case the throughput of the CFC-system was limited. The deep boundary currents, particularly in the western part of the section, were of special interest. 3.2.4 MOORING RECOVERY ON SECTIONS WHP-A2 AND WHP-A1 (BSH, K.P. Koltermann and IfMHH, J. Meincke) On the Gauss cruise 226 an array of three mooring was deployed west of the Mid- Atlantic Ridge an section WHP-A2 in the summer of 1993 to measure the vertical and horizontal extend of a deep high salinity boundary current and its temporal changes. Previous attempts to recover these mooring had failed as there seem to are problems with the acoustic releasers. On this cruise another attempt for recovery was planned, depending on the prevailing weather situation and time availability. On WHP-A1 the mooring D2 was deployed to measure the vertical structure of the depth controlled current. Several attempts to recover the mooring acoustically had failed. On the leg M30/3 another attempt to recover the mooring by dredging was not successful. Further attempts to dredge for other moorings on this section had to be abandoned for weather reasons. 3.2.5 TRITIUM/HELIUM AND 14C-SAMPLING ALONG WHP-SECTIONS A2 AND A1 (IUP-HD, R. Bayer) The zonal section along 48°N (WHP-A2) was sampled for the first time for a detailed analysis of helium, tritium and 14C signals. Comparing the 1972 GEOSECS data in the Northwestern Atlantic with the TTO/NAS data in 1980-81 has shown a prominent invasion of the transient tracer signals from the surface into the deep waters. An additional survey of these tracer fields in 1994 (WHP-A2) gives further indications on how much and how fast this invasion has proceeded. This will help to parameterize the renewal rates for the individual deep basins. Clear horizontal gradients of higher tracer signals in the West are seen. The deep western boundary currents with the most recent and youngest waters are clearly evident, showing similar features as on the A1 section sampled in 1991. A detailed survey of these gradients along the sections and the meridional connection of the tracer signals in the Deep Western Boundary Currents are of particular interest. On WHP-A2 474 helium and tritium samples have been collected. In addition 311 helium samples have been taken to test a sea-going extraction facility. Of the 51 stations sampled a denser coverage was attempted for the western boundary currents, but had to be aborted due to bad weather but succeeded across the Mid Atlantic Ridge, with an even station distribution along the rest of the section. In parallel to the large volume 14C-sampling we sampled for AMS-14C-analyses. The large volume samplers are used at the relevant stations in two casts: the shallow cast was followed by the CTD-rosette cast for small volume samples to give time for the 14C-extraction and the subsequent preparation of the large volume samplers for the deep cast for 14C. As experienced in recent years in our polar work a complete 14C station was worked in about 5 hours (ca. 20 LVS samples at 4000 m water depth). For the 48°N section 8 LVS stations with 204 LVS samples and 60 samples for AMS-14C have been worked. Sampling on WHP-A1 (West and East) followed for the Eastern part largely the 1991 strategy and results. Some 400 helium and tritium samples were analysed ashore. We used the seagoing extraction facility with great success. Similar to the sampling strategy on the previous leg on A2, sampling focused on the basin boundaries with ca. 25 stations in total. We tried to resolve the temporal and seasonal variability of the tracer signatures in order to compare them with existing data from the European Polar Seas and work done further south within the frame-work of WOCE. This also applies for the work in the Labrador Sea on A1 West. Here we had planned ca. 100 samples for helium and tritium, and 3 stations for LVS-14C work but succeeded only in working 2 stations due to bad weather. 3.2.6 WOCE NORTH ATLANTIC OVERTURNING RATE DETERMINATION (WOCE-NORD, WHP section A1) (IfMHH, J. Meincke and BSH, A. Sy) The meridional transports of heat and matter in the North Atlantic are quantified through a section connecting Ireland and South Greenland. This section runs south of the region where the atmospheric forcing transforms the water advected to high latitudes such that it will sink to intermediate and greater depths and spreads further south, forming the source water masses of the North Atlantic Deep Water. This "overturning" process is regarded as the main driving mechanism for the global thermohaline circulation. Quantifying both input and output in the North Atlantic overturning system will help to improve modelling the role of the ocean in the climate system. Leg M30/3 is part of the WOCE-NORD project, running over six years. To extend the data basis needed to calculate the transport rates involved in the overturning process, sections have been repeated seasonally between Ireland and South Greenland. A combination of current measurements from the ship in motion, long-term moorings of current meters and surface topographies from altimeter data are being used. This leg M30/3 was the third repeat of the WOCE hydrographic section A1E/AR7E. Extending this time the work to the western part A1W together with the work on A2 improves the transport estimates using inverse modelling. Along a section through the Labrador Sea Basin (A1W) from Hamilton Bank to South Greenland and continuing on a section from South Greenland to Ireland (A1E) we observed the fields of the classical hydrographic parameters pressure, temperature, salinity, content of dissolved oxygen and nutrients (NO3, NO2, PO4, SiO3). The work along A1E was, except for weather "gaps", an identical repeat of the work on Meteor cruise M18 (September 1991). The work programme followed the strategy used during the previous leg M30/2 and all instruments and procedures were continued. Only for nutrients and oxygen work other groups joined in St. John's employing their own slightly modified procedures. All data, particular the CTD data, were processed on board, except for applying post-cruise laboratory calibrations to the pressure and temperature sensors. 3.2.7 CFCS ON THE SECTION WHP-A1 (IfMK, M. Rhein) On the third leg of M30 we determined the tracer characteristics of the water masses that have spilt over the ridge system between Greenland and Iceland (DSOW) and between Iceland and the Shetlands (ISOW). After leaving the ridges these denser masses sink to the bottom and entrain ambient water masses. The extent of the mixing and the changes of the water mass characteristics after leaving the ridges are also a focus of these investigations. The data will be used to improve the parameterisation of the Deep Water formation process north of the ridge system and to derive at better mean spreading velocities for individual water mass components. Other tracer and oceanographic data will be used as well. Besides the overflow water masses we also sampled the newly formed deep water from the Labrador Sea, both at the exit of the Labrador Sea and along its spreading paths in the Irminger Sea and the North-Eastern Atlantic. On all stations of the WOCE section WHP-A1 water samples from all depths were analysed for CFCs. Some 1800 measurements of F11, F12, F113 and CCl4 have been processed. These data will be used to determine mixing rates and apparent ages of the water masses in the North Atlantic. Sampling and interpretation will be done in close co-operation with all groups involved. 3.3 JGOFS- PROGRAMME 3.3.1 THE CONTROL FUNCTION OF THE CARBONATE-SYSTEM IN THE OCEANIC CO2 UPTAKE, WHP-A2 (IfMK, J. Duinker, L. Mintrop) Measuring pCO2, total carbonate and alkalinity we investigated the CO2 exchange between ocean and atmosphere in a regional and seasonal resolution to contribute to a global budget. In parallel these data will be used together with measurements of the 13C-signal to follow the spreading of the anthropogenic CO2-signal in the ocean. We used on the WHP section A2, M30/2 the experience of our previous WOCE cruise Meteor M22/5 along 30°S (WHP-A10). (1) Sampling ~ Sampling for alkalinity and total carbonate ca. once every 24 h (i.e. every third or fourth CTD station in parallel with the tracer sampling), ~ sampling for 13C-measurements in total on 23 stations ( 359 samples), ~ surface sampling from the clean sea water system along the cruise track every 30 to 60nm. (2) Measurements ~ direct measurements on board of alkalinity and total carbonate, ~ in parallel we used a continuous system to measure the CO2 partial pressure. 3.3.2 THE OCEAN AS A CO2 SINK: COMPLIMENTARY STUDIES OF THE BALTIC SEA AND THE NORTH ATLANTIC, WHP-A1 (IOW, B. Schneider) Measuring the parameters pCO2, total carbonate and alkalinity we will, in combination with oxygen and nutrients data describe the CO2 exchange between the ocean and the atmosphere in the North Atlantic in early winter. The results from the WHP section A1 of leg M30/3 are compared with similar measurements in the Baltic Sea to differentiate between the CO2 systems of two ecologically different marine environments. (1) Continuous measurements of the CO2 partial pressure along the entire ship's track from St. John's into the North Sea (M30/3). (2) Measurements of total carbonate on water samples of the WOCE stations along the sections A1W and A1E. We processed ca. 40 samples/d. 3.4 INDIVIDUAL PROJECTS 3.4.1 129I FROM NUCLEAR FUEL PROCESSING AS AN OCEANOGRAPHIC TRACER (CSCSM-CNRS, G. M. Raisbeck) On the two legs M30/2 and M30/3 water samples were taken to determine the 129I concentration. This nuclide originates from the nuclear fuel reprocessing system and has shown some interesting facets used as an additional oceanographic tracer. Previous work in the North Atlantic has as yet not been satisfactory to provide an adequate signal/noise ratio to assess its information content in oceanographic applications. 129I measurements, using AMS techniques, have been taken from seaweed and seawater along the European coasts and waters. From the 129I/127I ratios we have been able to demonstrate spreading pattern from this man-made tracer. First examples from the North Atlantic show that 129I can be used to differentiate sources other then those associated with tracers already used in oceanography. With samples from this cruise on WHP-A2 and WHP-A1 we would like to develop an estimate of the dynamic range this signal has in the full-depth ocean and evaluate if the information contained in these data is useful to describe water masses, their fate and behaviour. 3.4.2 PROFILING ALACE FLOATS TO DETERMINE THE DEVELOPMENT OF THE STRATIFICATION IN THE LABRADOR SEA OVER TWO YEARS (SIO, R.Davis and WHOI, B.Owens) On the leg M30/3 six ALACE (Autonomous Lagrangian Circulation Explorer) floats for two US-American groups (SIO/WHOI) were deployed in the Labrador Sea to determine the velocity field at a pre-selected depth level of 1500dbar over more than two years. These floats surface at regular weekly intervals to radio their position and data from their drift and ascend and descend phases to a satellite. This provides information besides the float track-derived velocities, on the evolution of the profiles of temperature and salinity with time. For two years we will follow the evolution of the Labrador Sea stratification for the top kilometre with profiling ALACE floats (P-ALACE). They are deployed across the Labrador Sea gyre and part of the boundary current regime and surface at weekly intervals to report profiles of temperature (5 floats) and temperature and salinity (one float) via satellite. The tracks will give a first glance at the velocity field of the gyre and its changes. We will use this information for planning a convection experiment in 1996. Some other ALACE floats with RAFOS transducers will be deployed to test the effective sound ranges with the existing Newfoundland Basin array. Experience from the Arctic has shown that we have to consider reduced ranges in this region. The results are needed to design a RAFOS array for work from 1996 onwards. Fig. (1) Track and Station map of Meteor leg M30/1 star: moorings,dot: benthic station, arrow: cruise track 4 NARRATIVE OF THE CRUISE 4.1 Leg M30/1 (Chief Scientist O. Pfannkuche) FS Meteor left Las Palmas on the evening of Sept. 6, 1994 heading north for the first station at 49°N, 16°30'W on the Porcupine Abyssal Plain. En route the ship stopped 3 times in international waters on the Iberian Abyssal Plain in order to test a new version of the multiple corer and the CTD/Rosette system. On Sept. 12 at 0400h we started to work at the first station at the Porcupine Abyssal Plain. After water sampling and CTD profiling the sediment trap mooring of the Institute of Oceanographic Sciences, UK, which was deployed in spring 1994, was successfully retrieved. A series of multiple corer samples followed. In the afternoon the refitted sediment trap mooring was deployed again and Meteor headed east for the next station at the bottom of the continental rise. Besides sediment and water sampling a new sediment trap mooring (OMEX IV) was deployed. From now on sampling stations followed the contours of the continental slope (Fig. 1) from the Pendragon Escarpment (water depth 3600 m) up to the Great Sole Bank (water depth 220 m). Station work on the Pendragon Escarpment had to be interrupted on Sept. 13 until the afternoon of Sept. 14 as a storm (8-9 Bft) prevented the use of any sampling gear. On all slope stations sampling followed the same routine: sediment samples with box grab and multiple corers, water samples with Go-Flow bottles, a Niskin bottle rosette sampler and a marine snow catcher (only one haul), and CTD profiling. Two more sediment trap moorings of the OMEX project were successfully retrieved and re-deployed after refitting. OMEX III at 3670 m on the Pendragon Escarpment on Sept. 15 and OMEX II at 1418 m on the upper slope on Sept. 16. A free vehicle grab respirometer (bottom lander) was moored on the Pendragon Escarpment for two days (Sept. 13 - 15). At 1700h on Sept. 17 station work was finished on the outer Great Sole Bank and METEOR headed back to Germany. The cruise M30/1 ended at 0800h on Sept. 21, in the port of Bremen. 4.2 Leg M30/2 (Chief Scientist K.P. Koltermann) FS Meteor left its berth in Hamburg after a routine shipyard refit in thick fog on Oct 12, 1994 at 0900. After a smooth transit with increasing visibility, the first station (#436) for testing all equipment was worked on Oct. 15, 1994 from 1232 UTC on 48°09.9'N, 11°44.9'W on 3420 m depth in international waters. On Oct 16, the first station of the trans-Atlantic transect was begun at 0444 UTC on 49°14.1'N, 10°39.9'W and a depth of 153 m. The first autumnal gales caught up with us already the next day, where winds of S10-11 Bft stopped station work. Weather-related breaks were used to find the optimum combination of rosette, underwater command module and CTD. Several attempts to dodge the weather and use lower wind speed periods where unsuccessful, so that we could only return to the planned station in the morning of Oct 20, 1994. Work progressed until the evening of the next day, when the ship again had to weather winds from the West with 10-11 Bft. The next week saw better progress westward. On Oct 27 an attempt to dredge for the mooring K1 west of the Mid-Atlantic Ridge was not successful, although the mooring had responded to acoustic signals. Moorings K2 and K3 were acoustically located but did not release. No dredging attempts were made. Increasing winds prohibited station work afterwards until Oct 29, although that station had to be interrupted again for heavy winds. This stop-and-go station work continued until Nov 8. Station spacing had to be adjusted to allow for distance made west during gales and time lost. Time had also to be used either to return to a planned station position when the position had been overrun or heave to at a new position and wait for the weather to calm down. While work was stopped at times by heavy weather east of the Mid-Atlantic Ridge, work was only possible in the "weather windows" between a succession of depressions west of the ridge. In the westernmost part of the section up onto the Grand Banks the number of stations had to be reduced severely as time was running out when the extra-tropical storm "Florence" hit the area. This decision was made easier as the CCS Hudson had worked that part only days earlier during recovery of an extended mooring array. The last two stations of the section could be worked as planned, and in transit an extensive set of deep XBT casts will provide the essential continuity between stations. Work was finished on Nov 10, 1994 at 0059 UTC and the ship made for St John's, Nfld where she arrived on Nov 12, 1994 at 0600. A total of 53 stations with 82 rosette casts was worked instead of the planned 82 stations (Fig. 2). Fig. (2) Track and station maps of Meteor legs M30/2 (WHP-A2) and M30/3 (WHP- A1). Top panel: hydrographic stations and numbers, bottom: XBT stations and numbers 4.3 LEG M30/3 (Chief Scientist J. Meincke) Following three days in port for exchanging the scientific party, setting up the laboratory installations, hand-over meeting with the previous party and visits between the ship and local scientific institutions at the St. John's Memorial University and the Northeast Fisheries Center, the ship left St John's on Nov 15, 1994 at 1400. A test-station for the CTD-Rosette systems was carried out en route to the starting position for the Labrador Sea section WOCE A1W on Hamilton Bank. Station work only began on Nov 18, at 0600 since a NW-gale stopped any progress for 20 hrs during Nov 16/17. Stations 490 to 496 over the Canadian continental slope were completed on Nov 19, 1200 when the weather forecast strongly recommended to leave the Canadian side and change over to the Greenland side of the Labrador Sea as fast as possible. During the transit four P-ALACE (Profiling Autonomous Lagrangian Circulation Explorers) were deployed and 2000 m XBTs were launched every 20 nm. The following two days were dominated by strong winds at temperatures around the freezing point, only one station (497) could be completed. From Nov 22 onwards regular station work resumed, starting in the convective regime of the Labrador Sea and crossing the boundary current regime towards the Greenland shelf (stations 498 -505). Again the weather forecast determined to finish activities in the Labrador Sea and take up the WOCE line A1E from east of Kap Farvel to Ireland. Therefore we had to leave the section A1W uncompleted in its central part and sailed around Kap Farvel. Station work resumed on Nov 24 at 2200 on the eastern Greenland shelf (stat 506) down the slope into the Irminger Basin, but had to be interrupted following station 511 for Nov 26 and 27 because of a severe gale. However, we experienced a full week of moderate winds and seas and completed stations 512 - 537 until Dec 4, 1994. This phase included 12 hours on Dec 2 of unsuccessful dredging for the current meter mooring D2 which had been deployed in 1992. Three previous recovery attempts in 1993 and 1994 had already failed. The next phase of severe winds and seas started on Dec 5 in the area 53°N, 24°W. On Dec 6 we experienced the highest wind speeds (100 kts) and highest seas (12 m) during this cruise. On Dec 9 a continuation of these conditions until at least Dec 14 became evident from the long- and medium-range numerical weather predictions. We decided to give up to complete of this WOCE section and return to Hamburg. At 2000 the ship started to head east, launching XBTs every 15nm and XCTDs every 30nm. However, on the morning of Dec 10 the numerical forecasts changed radically and predicted the development of a high pressure ridge over the operation area to stabilize for a few days from Dec 12 onwards. This chance was to be taken, the ship turned around and indeed from Dec 12 to Dec 15 0600 the WOCE section was completed in fine weather conditions (stations 538 - 551). Since a few series of intense atmospheric depressions was announced to move into the operations area for Dec 16, the original plans to dredge for further moorings with release malfunction were given up. The ship made for Hamburg were it docked on Dec 19, 1994 at 0100 LT. 5 OPERATIONAL DETAILS AND PRELIMINARY RESULTS 5.1. OMEX PROGRAMMES 5.1.1 BIOCHEMISTRY ~ PHASE TRANSFER OF ORGANIC COMPOUNDS DURING SHELF EDGE PASSAGE (UHIBl, I. Büns, A. Pfeifer and U. Brockmann) Within the biogeochemical transfer and transformation processes in the area across the shelf edge, nutrients and organic compounds are key parameters. During the cruise, water samples were taken from defined depths at fixed stations on a west-east profile along the Goban Spur. The samples were filtrated and conserved for a later analysis, since besides oxygen titration, pH and photometric measurements, no chemical analysis could be done on board. Sampling should be done with a multi-bottle-rosette (24), connected to a CTD probe (Oceanography, Kiel). A test-run at station 423 was successful. Unfortunately, this was the only station, where multi-bottle-rosette and probe worked properly! We have to thank Prof. Balzer for the use of their GO-Flow rosette as a temporary replacement for the multi-bottle-rosette at some stations! Furthermore, they took care that another multi-bottle-rosette (University Bremen), which was stored on board, could be used later. Fig. (3a) Nitrate (including nitrite) profiles. This diagram is dominated by the variations of nitrate. In general, there was a strong gradient (0.1 - 9.5 mol/l), increasing with depth, already in the euphotic zone. At station 430 a peak was observed in 30 m depths. At station 425/IOS (depths > 4800 m), when multi-bottle-rosette and CTD totally failed, only 5 samples with the GO-Flows down to 200 m could be taken. Station 426/OMEX IV: multi-bottle-rosette and CTD still did not work; because of lack of time the GO-Flows couldn't be used. At station 427/OMEX III the CTD probe was run separately; the multi-bottle- rosette still refused to work properly. As there was no time for a separate sampling, we got part of the samples of Prof. Balzer, but the total volume that we actually needed for the filtration was not available. Station 428/F: another trial, to run the multi-bottle-rosette from Bremen together with the CTD failed. We got samples from the GO-Flows, but as the interval between sampling and the time where we got our subsamples was too long, we couldn't use them. At the station 430/OMEX II the CTD probe and the multi-bottle-rosette were run separately. Finally, success! At the stations 433/B 1, 434/OMEX 1 and 435/A sampling now was successful. METHODS: A vacuum filtration was run with controlled 0.2 bar at 9 filtration stands. Depending on the concentration of suspended matter, volumes from 750ml to 1750ml were filtrated over Whatman GF/C filters for the determination of CHN, part. P, part. CH and dry weight. An additional filtration stand was used for volumes up to 5 l for each filter for the determination of lipids. All filters were stored frozen at -17°C. The filtrate was fixed with mercury-(II)-chloride (0.01% w/v) and stored in glass and polyethylene bottles in a cooling chamber for a later analysis of nitrate, nitrite, phosphate, silicate and ammonium. A wet-chemical oxidation method was used to prepare samples for determination of total dissolved nitrogen and phosphorus. Immediately after sampling, measurements of turbidity (Turner nephelometer), pH (WTW pH 91) and fluorescence (Turner fluorometer and 1 Hz fluorometer) were conducted. Oxygen was determined by Winkler titration with a Metrohm titration stand. FIRST RESULTS: The following diagrams (Fig. 3a-c) show nutrient-depth profiles for the sequence of stations from west to east. The profiles consist of raw data, not yet controlled. In general, the profiles show high nutrient concentrations within the deep water masses and low values due to nutrient consumption in the euphotic zone in the mixed layer. ~ ORGANIC MATTER DEGRADATION, DENITRIFICATION AND TRACE METAL DIAGENESIS. ~ DISSOLVED AND PARTICULATE TRACE ELEMENTS (UBMCh, W.Balzer, A.Deeken, H.Dierssen) Within the OMEX-project on trace element cycling at the Celtic margin it is our task to determine the fluxes and reactions near the sediment/water interface. In order to gain a link to water column processes, the distribution of dissolved trace elements in the pore water and solid sediments has to be compared with their concentration in the water column and its suspended particulate material (SPM). During M30/1 the main objectives were to investigate for a summer situation whether dissolved Al and suspended particles (eventually resuspended from the sediments) are injected from the margin into the open ocean and whether they affect the trace element chemistry of the open ocean. Two particulate phases were sampled using different techniques: (i) the SPM filtered by using in-situ pumps is supposed to consist of slowly sinking biogenic and terrestrial detritus exhibiting a large surface area for sorptive processes, (ii) the sediment representing the ultimate result of all water column processes and early diagenetic modifications near the sediment/water interface. Fig. (3b) Phosphate profiles. Starting in the euphotic zone, similar strong gradients with increasing depths down to 1000 m characterized the profiles (0.1 - 1 mol/l). Again a peak (0.6 mol/l) occurred at 30 m depth at station 430. Due to the low concentration of SPM below the mixed layer, large volumes of sea water were filtered for trace element determinations in SPM. Between 250L and 550L sea water were filtered through acid cleaned 293 mm Nuclepore filter using in-situ pumps. To reduce contamination risks a non-metallic wire was used and all handling of the filters was performed under a clean bench within a clean room container. Because in-situ pumping is very time-consuming pumps were combined with bottle casts whenever possible. Due to limited ship time only 7 filters were obtained from the Goban Spur transect at depths between 50 m and 1450 m. Another 3 filters were disrupted during deployment. At all stations where in-situ-pumps were deployed and especially where sediment trap moorings were positioned, casts of GoFlo bottles were taken to analyse the vertical distribution of Al and eventually other trace metals in the water column. For the trace metal studies precautions had to be taken against the risks of contamination: before use the GoFlo bottles were acid cleaned thoroughly, at station the bottles were attached to a non-metallic wire, during handling on deck both opening ends were covered with plastic bags, all manipulations after sub-sampling were performed under a clean bench. During the cruise Al from 6 stations was measured on board using a fluorometric technique. The vertical and horizontal distribution will be compared with results from the particle analysis. Fig. (3c) Silicate profiles. The silicate gradients in the euphotic zone started at 0.5 mol/l. In depths below 500 m the gradients were comparable to those of nitrate and phosphate. Again a small peak could be seen at 30m depth at station 430. Solid sediments and pore water samples for the determination of dissolved trace metals were taken at 7 stations along the Goban Spur transect (see below). On board ship the pore water samples were preserved after filtration and acidification; preconcentration and the separation from the salt matrix will be performed at the home laboratory. ~ DISSOLVED ORGANIC CARBON (UBMCh, S.Otto, W.Balzer) In order to investigate dissolved organic carbon (DOC) in the water column across the continental margin, samples from seven CTD-rosettes or GoFlo casts were taken at the Goban Spur transect. At each position the whole water column was sampled. It is very critical in the determination of DOC to avoid contamination of the samples. Therefore, great care was taken from the first step of sampling throughout the whole work-up procedure: samples from the rosette were taken in pre-cleaned glass bottles, immediately filtered through pre-combusted GF/F filters and finally acidified and sealed in brown glass ampoules. All samples were stored at +4°C until analysis. The DOC determinations were performed by the High-Temperature-Catalytic-Oxidation (HTCO). In addition to the investigation of DOC in the water column, sediments taken at 6 stations with a multi-corer were sampled to determine DOC in pore waters. After squeezing the sediment in a cold room, the pore water was analysed for DOC and for total inorganic carbon (TIC). While TIC at the deeper stations was always close to 2 mmol/L it was much higher at the shallow stations showing a maximum of 5.6 mmol/L. DOC in the pore water varied between 0.8 and 2.6 mmol/L, again having higher concentrations at the shallower stations. ~ PORE WATER CHEMISTRY (UBMCh, W.Balzer, A.Deeken, H.Wellmann) The OMEX-project was established to contribute towards the understanding of the cycling of nitrogen, carbon and trace metals at continental margins where benthic processes are expected to play a significant role for the chemistry of the whole ocean. Necessary for the understanding of the major controls over release fluxes from boundary sediments is a detailed investigation of early diagenetic processes acting within the sediments. It was therefore planned to conduct extensive work on pore water chemistry and on solid sediment phases at the Goban Spur transect across the Celtic margin. From the sediments taken at 7 stations (#425, #426, #427, #428, #430, #433, #434) by a multicorer, the pore water was squeezed or centrifuged under in-situ temperature conditions (cool room). Nitrate as the pore water constituent providing most information about the diagenetic milieu, showed systematic variations in the profiles over the transect. All nitrate pore water profile showed sub-oxic conditions typical for hemipelagic sediments of the North Atlantic ocean but there was also a significant contribution of sulphate reduction to organic matter degradation at the stations shallower than 1500 m. The rates of carbon combustion by oxygen and nitrate, respectively, were assessed by use of a model for steady-state diagenesis of organic matter. The rates for organic carbon degradation by oxygen decreased systematically with water depth with one exception: station #430 at 1500 m showed an extremely high rate which is consistent with benthic lander results obtained by Dutch colleagues. ~ BENTHIC DENITRIFICATION AND BIOIRRIGATION (UBMCh, W.Balzer, A.Deeken, H.Wellmann) For the estimation of denitrification rates two independent methods were applied: (i) the evaluation of the rate from the modelling of the pore water nitrate distribution, and (ii) the direct determination according to the "acetylene-block" incubation method. The pore water nitrate profiles can be used simultaneously to estimate integrated rates of denitrification, for the reaction being first order with respect to nitrate. Denitrification was detectable but weak in the depth range from 5300 m to 3665 m but became much more intensive when the shallower region (1500 m to 670 m) was approached. The determination of denitrification rates by C2H2-block incubation comprises the following steps: (i) sub-sampling a box-corer with several acrylic glass tubes, (ii) injection of acetylene into the pore water of the whole sediment column of the sub-cores to block the further reduction of the intermittently formed N2O to dinitrogen, (iii) sectioning of the sub-cores after appropriate incubation times, (iv) equilibration of the sediment sections with the gas phase in small closed jars after stopping the reactions with KOH, and (v) head-space analysis of the N2O concentration in the gas phase by GC-ECD. Only 4 sediment stations (#428, #430 (OMEX II), #433 and #434 (OMEX I)) were selected for this lengthy procedure. For each station 6 sub-cores were used: 2 sub-cores for an average N2O-profile, 2 sub-cores for an average 1-day- incubation and 2 sub-cores for an average 2-day-incubation. There was no N2O- production at station #428. The other 3 shallower stations showed intensive N2O-production close to the surface with maximum rates at the depth range 2-4 cm in all cases. When comparing these rates with the denitrification rates obtained from pore water modelling two features deserve special attention: (i) considering the widely differing boundary conditions, assumptions, etc. of the two methods, the agreement within a factor of 3 is remarkable, (ii) there might be a difference in the process that is measured by the two methods: the pore water profile might correspond more to the long-term steady-state situation while the incubation might respond to seasonal effects more directly. The N2O profiles in the pore-water (without incubation; from which release rates were calculated) showed highest concentrations near the sediment surface in all cores investigated. N2O release, however, is significant only in sediments of the upper continental margin again having a relative maximum at 1530 m as suggested by the relative heights of the rates obtained from incubation. The relative heights of the N2O release rates can be estimated directly from a comparison of the profiles. The absolute rates can only be calculated when the modelling of the tracer incubation experiments for the calculation of bio- irrigation rates is finished - which is presently underway. Especially in the shallower parts of the continental margin, the release fluxes from the sediment surface might be enhanced by the bio-irrigating action of (bioturbating) macrofauna organisms. To estimate the enhancement over molecular diffusion, tracer experiments were performed by applying a tracer in the overlying water and incubation of the sediment core at in-situ temperature. After 2-4 days the core was cut into slices and the tracer concentration was determined in the pore water. By numerical modelling (using a "quasi- diffusional" coefficient) the transport of the tracer into the sediment column can be followed and the best-fitting coefficient can be evaluated. 5.1.2 AIR CHEMISTRY ~ EXCHANGE OF REDUCED SULPHUR COMPOUNDS BETWEEN OCEAN AND ATMOSPHERE (MPICh, G. Uher, O. Flöck, G. Schebeske, V.Ulshöfer) The biogeochemical processes, which are controlling the production of carbonyl sulphide (COS) and dimethyl sulphide (DMS) in surface seawater as well as their emission to the atmosphere were the focus of the biogeochemical investigations by our group. These studies were accompanied by measurements of chlorophyll concentration, absorbance and fluorescence of dissolved organic matter on one hand, and of the atmospheric concentrations of condensation nuclei, black carbon, and radon (222Rn) on the other hand. In the following sections some preliminary results are presented. ~ COS IN SURFACE SEAWATER AND ATMOSPHERE (V. Ulshöfer) COS is formed photochemically in surface seawater and is believed to be the main source of the stratospheric sulphate layer during periods of low volcanic activity. This sulphate layer affects the Earth's radiation balance as well as stratospheric ozone levels. Emission from the oceans is one of the main sources in the global budget of COS. In this budget, however, exists an imbalance between sources and sinks which partly may be due to large uncertainties in the quantification of single sources and sinks. For a better assessment of the oceanic source, we investigated the diurnal and seasonal cycle of COS in the Northeast Atlantic. Atmospheric and dissolved COS was determined using a semi- continuous seawater equilibration system with cryogenic preconcentration, gas chromatographic separation and flame photometric detection. Ambient air was drawn through a Teflon tube from the top of the ship's mast to the analytical system. Air was analysed directly and after equilibration with seawater (for the determination of dissolved COS in seawater). Water from approx. 7 m depth was supplied continuously to the equilibrator by a non-contaminating pumping system. This pumping system consisted of a Teflon membrane pump (all wetted parts polyvinylidene fluoride) and a polyvinyl chloride tube mounted inside a hollow stainless steel shaft which was submerged beneath the keel through the ship's "moon pool". The fully automated system allowed the hourly analysis of atmospheric and dissolved COS. The saturation ratio of COS in surface waters with respect to its atmospheric concentration was calculated: SR = [COS]equilibrated air / [COS]ambient air During the entire cruise leg dissolved COS was supersaturated in surface waters with respect to its ambient atmospheric concentration and a diurnal cycle with maxima in the afternoon and minima before sunrise was observed. The results from the former Meteor cruise legs M27/1 (January 1994, OMEX area) and M21/2 (April/May 1992, BIOTRANS area at 47°N, 20°W) are in contrast to these findings. The winter data (M 27/1) showed persistent undersaturation and no diurnal cycle of dissolved COS, probably due to low light intensity and hence low photochemical production during daytime. The spring data from the BIOTRANS area (M 21/2) showed undersaturation as well as supersaturation and no net flux to the atmosphere could be found within the experimental uncertainty. The results from these three cruise legs cover three seasons (winter, spring, and summer) and show a pronounced seasonal variability of the sea surface COS concentration. This set of data will be used to estimate an annual cycle of dissolved COS in the Northeast Atlantic, based on meteorological and oceanographic data. Moreover a kinetic model for the diurnal cycle of dissolved COS will be applied that considers light dependent and light independent COS production, hydrolysis, and gas exchange across the air-sea interface. Consequences with respect to estimations of the global marine emissions of COS will be addressed. ~ DEPTH PROFILES OF DISSOLVED COS AND PHOTOCHEMICAL INCUBATION STUDIES (O. Flöck) Depth profiles of dissolved COS were taken using non-contaminating, gas tight GoFlo water samplers. The water samples were pressure filtered (GF/F Whatman filters, preheated at 400 C for 2h), transferred into volume-calibrated glass flasks (approx. 300 ml) and stored in the dark at 4 C for not longer than 6 hours. Photochemical incubation studies were performed using surface seawater obtained from our non-contaminating seawater pumping system. The water was GF/F filtered, filled into glass flasks and exposed to sunlight for ca. 10 hours. The samples (including dark controls) were held at sea surface temperature during the irradiations. COS was determined by gas stripping of seawater, followed by cryogenic trapping, gas chromatographic separation, and flame photometric detection. All results were corrected for sample losses due to hydrolysis. At ten stations the vertical distributions of dissolved COS were recorded. These data included high resolution profiles within the upper 100 m and profiles down to depths of 2000 m. Generally the vertical profiles showed maxima at the sea surface and an approximately exponential decay to a certain background level beneath the mixed layer (about 50 m during the cruise). Although the COS concentration in deeper waters was very low, some transport or non-photochemical production mechanisms are required to maintain this background level and compensate losses due to hydrolysis. In addition to the station work, time series of COS photoproduction were obtained from ten sunlight irradiations of surface seawater. These time series together with our continuously recorded UV- light intensities will enable us to determine COS photoproduction constants. Our complete data set which includes atmospheric mixing ratios, sea surface concentrations, depth profiles, and COS photoproduction constants, will be used to test one-dimensional transport models for the prediction of surface concentrations and global marine emissions of COS. We will be able to investigate the influence of downward mixing of dissolved COS out of the zone of photochemical formation on the sea surface concentration and hence on the sea- to-air flux of this climatically relevant trace gas. ~ SEA SURFACE CONCENTRATIONS OF DISSOLVED DMS (G. Uher) DMS is formed mainly by the enzymatic cleavage of dimethylsulfonium propionate (DMS) which is a metabolic product of marine phytoplankton. Former work showed that the concentration of dissolved DMS is controlled by a complicated interplay of algal speciation and trophic interactions. Air-sea exchange processes result in the emission of dissolved DMS into the atmosphere where it is oxidized mostly to aerosol sulphate. These aerosol particles act as cloud condensation nuclei (CCN), and thereby influence the reflectivity and stability of clouds. Thus the Earth's radiation balance is sensitive to the CCN number concentration which in turn might be sensitive to changes in phytoplankton biomass. Global estimations of marine DMS emissions still suffer from the insufficient knowledge about its regional and seasonal distribution all over the oceans. The emission of DMS is largely controlled by its sea surface concentration and wind speed. During this cruise leg we performed measurements of sea surface DMS with high time resolution to improve our data base with respect to regional distribution, patchiness, and seasonality of DMS in surface waters. DMS was determined using a semi-continuous seawater purge and trap system with cryogenic preconcentration, gas chromatographic separation and flame photometric detection. Seawater was sampled using our non-contaminating pumping system. The newly developed automated analytical system hourly sampled seawater which then was filtered (GF/F Whatman filters) and analyzed for dissolved DMS. The concentrations ranged from 1 nmol l-1 up to 12 nmol l-1 with an average of 2.8 nmol l-1 for the entire data set. During the transect from the Canary Islands to the Celtic Sea margin, the DMS concentrations increased slowly from 1.5 nmol l-1 to about 3 nmol l-1, but no pronounced gradient across the shelf edge could be observed. This is not surprising, however, since we could neither find any pronounced increase in chlorophyll (indicator of phytoplankton biomass) nor in absorbance or fluorescence of dissolved organic matter which were used to classify the water masses of the different biogeographic regions (e.g. coastal & shelf, open ocean). On the shelf region, dissolved DMS showed maxima up to 12 nmol l-1 which were associated with areas of high chlorophyll concentration. Our attempts to find consistent relationships between chlorophyll and dissolved organic matter on one hand and sea surface DMS on the other did not result in simple correlations. Nevertheless, we will continue in carefully looking for relations between DMS and chlorophyll within distinct oceanic regions to further investigate the possibility of using satellite imagery as a tool for extrapolating and predicting DMS concentrations. Based on our time series of dissolved DMS we will estimate sea-to-air fluxes of DMS. These fluxes then will be compared to the number concentrations of condensation nuclei (CN, Aitken nuclei). Our black carbon and radon (222Rn) data will help us to distinguish between marine and continental air masses. Hence we will be able to look for relationships between CN and the precursor compound DMS within the marine boundary layer. ~ CHLOROPHYLL AND DISSOLVED ORGANIC MATTER IN SURFACE SEAWATER (G. Schebeske, V. Ulshöfer) In addition to the defemination of sulphur compounds, chlorophyll along with absorbance and fluorescence of seawater was recorded. We intended to use chlorophyll as an indicator of phytoplankton biomass and furthermore absorbance and fluorescence of dissolved organic matter as tracers to determine the degree of mixing between different water masses as well as their optical and photochemical properties. Surface seawater from our non-contaminating pumping system was sampled approximately every 4 hours. The samples were stored in detergent washed polyethylene bottles at 4°C in the dark, generally for not longer than 10 hours. 250 ml were filtered (GF/F Whatman filters, preheated at 400°C for 2h). The filters were homogenised and extracted with acetone/water (90/10) at room temperature. Then the solution was filtered again to remove the glass fibres, filled up to a standard volume with acetone/water, and analyzed fluorometrically (Ex 425±20 nm, Em 665±20 nm) using a Shimadzu RF1501 spectrofluorometer equipped with a 10 mm quartz cell. The instrument was calibrated before and after the cruise using a solution of chlorophyll a (Sigma Chemie) in acetone/water.Both absorbance and fluorescence was measured on filtered seawater (GF/F Whatman filters, preheated at 400 C for 2h). The spectral absorbance was recorded from 250 nm to 700 nm using a Shimadzu UV160A spectrophotometer and 100 mm quartz cells. Milli-Q water was used as a reference. The absorbance data have been normalized to compensate for the instrument's drift by subtracting the reading at 690 to 700 nm. Fluorescence emission spectra., 325 nm, and 340 nm as excitation wavelengths and an emission wavelength scan in the range of excitation wavelength plus 15 nm up to 600 nm. The spectral response of Milli-Q water was subtracted and the fluorescence intensities then were expressed in quinine sulphate units (the maximum intensity of 1 mg l-1 quinine sulphate dihydrate in 0.105 M HClO4 at the excitation wavelength used was defined as 1 quinine sulphate unit). Preliminary results show absorption coefficients a(350 nm) lower than 0.1 m-1 for the transect from the Canary islands to the celtic sea margin and no significant increase across the shelf edge could be observed. (a(350 nm) here is defined as the decadic absorption coefficient and normalized to one meter optical pathlength. Thus Lambert Beer's law is written: A = a*l (A=absorbance, l=optical pathlength)). On the shelf area slightly higher absorption coefficients a(350 nm) of about 0.15 m-1 were found. The results from the fluorescence measurements in general showed the same trend. (1) CONDENSATION NUCLEI (CN, AITKEN NUCLEI), BLACK CARBON, AND RADON (222RN) WITHIN THE MARINE BOUNDARY LAYER (G. Schebeske, V. Ulshöfer) The atmospheric concentrations of condensation nuclei, black carbon, and radon were used as tracers to distinguish between marine and continental air masses. The sampling inlets for the continuous aerosol analysers (CN, black carbon, and 222Rn) were located on a beam extending into the air flow just above the flying bridge (ca. 30 m above sea surface) where the ship's air chemistry laboratory is located. Tubing lengths between inlet and instruments were less than 5 m. For CN sampling electrically conductive tubing was used. The sampling inlet for black carbon was automatically interrupted by a Weathertronics sampler controller if the relative wind direction was more than 120 off the bow to avoid the sampling of stack emissions. CN concentrations were determined with a TSI model 3020 condensation nucleus counter. Black carbon was measured with an aethalometer (Magee Scientific). Both CN and black carbon were recorded continuously and integrated over 5 min periods. 222Rn was recorded continuously via the decay products 214Po and 218Po using an APIA monitor. The counts were integrated over 2 hour periods. ACKNOWLEDGEMENTS We thank Karl Pegler, Ralf Lendt, and Harald Rätzer for letting us use their stainless steel sampling inlet. Thanks are due to Alexander Pfeiffer and Ilse Büns for helping us with their pH-data. 5.1.3 SEDIMENTOLOGY ~ PARTICLE FLUX AND IN SITU MARINE AGGREGATE STUDIES AT THE CONTINENTAL MARGIN (IfMK, A.N. Antia, W. Erasmi; IOSDL, R.S.Lampitt; T. Kumbier; IOW, G. Lehnert) ~ PARTICLE FLUX Particle flux studies within the OMEX programme focus on addressing the transport of material on the shelf-slope regions of the Goban Spur, with an emphasis on exchange of material between these regions and the adjacent open ocean. The positions of moorings with sediment traps, current meters and transmissometers have been chosen to quantify both particle flux out of the euphotic zone and winter mixed layer as well as to determine mid-water transport at the slope edge on the Pendragon Escarpment, at which position particles from the continental margin may be expected to be exported to the adjoining abyssal basin and the transport of dissolved nutrients onto the slope would take place. During METEOR 30/1 these moorings were successfully recovered and re-deployed and yielded a near-complete set of sediment trap samples and current meter data for the previous 9 months of deployment (Jan - Sept 1994). For the deployment period July 1993 - Jan 1994 (autumn/winter), currents at the position OMEX 2 were seen to flow along the bottom contours in a northerly direction, i.e. along - slope, whereas at the Pedragon Escarpment off -slope water transport was registered, accompanied by an increase in particle concentrations in the sediment traps at intermediate depths as compared to that directly beneath the winter mixed layer. The data obtained during M 30/1 show a different picture for the spring and summer. Fig. 4 (a - e) shows current meter data from the moorings OMEX 2 and OMEX 3 at the different depths. Data are presented as 24- hour running means to smooth out tidal oscillations which are present in all data, though with decreasing amplitude with increasing distance from the shelf. At OMEX 2 a change in current direction from predominantly northwest-flowing (~300( magn.) to south-easterly currents during March and again during May is apparent. Mean current speed decreases from 11.75 cm/sec at 620 m to 9.41 cm/sec at 1070 m over the 9-month deployment. Although few data of this kind exist for the Goban Spur, such a reversal of shelf currents during the summer months has been documented by Pingree & LeCann (1989) in an adjacent region. This reversal in current direction has implications on the source area of particulate material intercepted in the sediment traps. Southwesterly currents would carry material from the region of the shelf break, characterised by high chlorophyll concentrations, to the trap positions. Another feature that is evident from the data is the occurrence of warmer water during the winter months, as has been found in the Bay of Biscay region (Pingree & LeCann 1990). A transmissometer mounted on the vane of the current meter at 1070 water depth at OMEX 2 (data uncalibrated; jump at day 120 due to readjustment), show short events of increased water turbulence; the correlation of such variations in the suspended pool with particulate sedimentation is, however, tenuous at best. Results of sediment trap sample analyses will be available in the coming year; a rough idea of seasonality in bulk flux can be seen, however, from Fig. 5 (a and b); clear here is the increase in sedimentation during late April following spring phytoplankton growth. At the OMEX 3 site on the Pedragon Escarpment, current direction fluctuates frequently during spring and summer. Residual currents flow eastward at 580 m, and south-westwards at 1450 and 3280 m during this deployment period. Average current speeds during this deployment period again decrease with depth, from 10.4 cm/sec at 580 m to 6.8 cm/sec and 4.4 cm/sec at 1450 and 3280 m respectively. However at all depths events of on - slope water flow are seen, providing valuable information on the cross-slope exchange of nutrients to the productive shelf and slope regions. The general impression of bulk sedimentation at OMEX 3 shows a marked increase in sedimentation with depth in the lower two traps (Fig. 5 c, d), as was seen at this site during the prior period of deployment (July 1993 - Jan 1994). The qualitative nature of this material, which we take as evidence of export of slope material to the abyssal plain, will be better described upon analyses of trap samples. Of particular interest in the context of OMEX is determination of the fate of this material leaving the slope environment and its deposition in the Porcupine Abyssal Plain, where conditions for the subsequent long-term burial of organic matter differ from those of the benthos in the slope and shelf environments. To be able to better elucidate and quantify this export of slope material to the deep sea bed, an additional mooring was deployed in 4485 m water depth off the Pedragon Escarpment in co-operation with colleagues at NIOZ (Texel, The Netherlands) (Mooring OMEX 4, 48°59.51'N; 13°44.06'W). This mooring contains a single sediment trap (at 4015 m depth ) and current meter ( at 3995 m), which, on the basis of previous data available from this site, are above the region of near- bottom resuspension. TABLE 5.1.1: OMEX SEDIMENT TRAP MOORINGS CURRENTLY IN DEPLOYMENT. MOORING LATITUDE LONGITUDE WATER DEPTH INSTRUMENT DEPTH (M) OMEX 2 49°11.20'N 12°49.18'W 1445 m 595 Sed. trap 618 RCM 1052 Sed. trap 1076 RCM+Trans. OMEX 3 49°05.00'N 13°25.80'W 3650 m 556 Sed. trap 580 RCM 1465 Sed. trap 1489 RCM+Trans 3260 Sed. trap 3284 RCM+Trans OMEX 4 48°59.51'N 13°44.06'W 4485 m 4015 Sed. trap 3995 RCM+Trans A list of OMEX moorings presently in deployment is given in Table 5.1.1. These moorings will be recovered and redeployed from board the RSS DISCOVERY in September 1995. The OMEX sediment trap mooring line naturally extends onto the Porcupine Abyssal Plain. Sediment traps have been deployed by the Institute of Oceanographic Sciences (UK.) at "Station H" (40°N, 16.5°W) since April 1992 with a view to determining long-term trends in particle flux at an oceanic site removed from the influence of the continental shelf and slope. Traps have in general been at depths of 100, 3400 and 4500 m above bottom (water depth 4600 m) with an array of current meters and camera systems to examine temporal trends in marine snow concentration. The latest deployment had been from RSS DARWIN in April 1994. During METEOR 30/1 this was recovered, refurbished and redeployed within 11 hours. From the recovered traps, apart from one on which the mechanism failed halfway through its cycle, all functioned well and have provided a good collection of samples. These will be analysed in a variety of ways to give information about the composition of the material, and the flux of organic carbon, nitrogen, pigments, radionuclides and various organic markers. ~ MARINE SNOW STUDIES Marine snow is loosely defined as inanimate particles of diameter greater than 0.5 mm. They are thought to be the principal vehicles by which material sinks through the water column. Such studies therefore are of considerable importance in developing our understanding of material flux. The distribution of these fragile particles is best determined using photographic techniques such as the Marine Snow Profiler. This instrument is attached to the CTD and photographs about 40 l of water every 15 seconds using orthogonal illumination from a deep- sea flash light. Up to 400 frames can be taken. During Meteor M30/1 seven deployments of the MSP were successfully made and the resulting images will be examined on an image analyser to determine the abundance, size and volume concentration of these particles. In order to make further studies on marine snow particles they must be collected. This was achieved during Meteor 30/1 using the specially designed marine snow catcher or "Snatcher". This is a messenger operated 100 l closing water bottle designed to minimise damage to the marine snow particles. After standing on deck for at least 2 hours, the upper 95 l is drained off and the lower portion of the Snatcher disconnected along with 5 l of water. The particles can then be recovered from the base plate using a pipette. During this cruise, after some initial compatibility problems, the Snatchers were successfully deployed on two occasions to depths of 30 and 50 m. TABLE 5.1.2: MSP DEPLOYMENTS: DEPL. # STA # DATE TIME(H) CAST WATER LONG.°N LAT.°W DEPTH(M) DEPTH(M) 89 427 14.09.94 18:55 500 3668 49.09 13.41 88 428 15.09.94 00:02 500 3668 49.15 13.09 87 429 15.09.94 18:03 500 3643 49.08 13.41 86 430 16.09.94 02:31 500 1524 49.18 12.85 85 433 16.09.94 23:31 500 1148 49.24 12.50 84 434 17.09.94 06:59 500 672 49.42 11.54 89 435 17.09.94 13:55 200 211 49.47 11.15 ~ CTD - WORK CTD profiles, with registrations of conductivity, temperature, pressure, fluorescence and oxygen, were taken at a number of stations along the transect followed during M 30/1. Unfortunately, malfunction of the release mechanism of the rosette prevented water samples being taken during these deployments. CTD drops were thus mainly confined to the upper 500 m of the water column where a marine snow profiler, attached to the CTD frame, registered snow concentrations with a fine vertical resolution. 5.1.4 BENTHIC BIOLOGY ~ BENTHIC MICROBIOLOGY (IfMK, K. Poremba, K. Jeskulke) Microbiological investigations involved the determination of abundance and activity of bacteria in the sediment. Sediment samples were taken with a multicorer. The samples were immediately transferred into a cooled laboratory avoiding artefacts due to temperature shifts of the samples. The measurements included the fixation of subsamples with formaldehyde and later counting of bacterial cells (in the home laboratory), and the measurement of extracellular hydrolytic activity using 5 different fluorogenic analog substrates for protease, esterase, chitinase, and beta-glucosidase. Esterase activity represents a value of overall microbial activity, while the other enzyme rates enables the detection of different types of microbial degraders. Several stations of a transect over the continental shelf margin of Goban Spur were visited during leg M 30/1. The sampling was focused on sites deeper than 2000m, because extensive sampling between 200 and 2000 m had already been made on a former cruise with RV VALDIVA in July 1993 (VA 137). The experiments conducted on VA 137 had shown that the activity of hydrolytic enzymes in sediment decline with water depth. Cleavage rates of relatively easy degradable substances declined faster than degradation rates of more refractory molecules, which gave evidence for a close relationship between biological activity and quality of organic matter at the sea floor, and supported the theory of pelagic- benthic coupling in the sea. The measurements of M30/1 should elongate the transect of the previous measurements, because the sampling season of VA 137 and M30/1 was similar, so that only small seasonal impact could be expected. Fig. (4a) 24-hour running means of current meter data from OMEX 2 at 620 m from Jan - Sept 1994 (Day Nos. 11 - 260). Fig. (4b) 24-hour running means of current meter data from OMEX 2 at 1070 m from Jan - Sept 1994 (Day Nos. 11 - 260). Jump in transmissometer data at day 108 is due to readjustment; transmissometer data are uncalibrated. Fig. (4c) 24-hour running means of current meter data from OMEX 3 at 580 m from Jan - Sept 1994 (Day Nos. 11 - 260). Fig. (4d) 24-hour running means of current meter data from OMEX 3 at 1450 m from Jan - Sept 1994 (Day Nos. 11 - 260). Transmissometer data (uncalibrated) are off scale at 4.505 Volt. Fig. (4e) 24-hour running means of current meter data from OMEX 3 at 3280 m from Jan - Sept 1994 (Day Nos. 11 - 260). Fig. (5) A rough estimate of seasonality in sedimentation of the mooring OMEX 3 between January and September 1994 (x-axis, day numbers 11 - 260) as shown from the height of particle accumulation (y-axis, cm) in the sediment trap cups. Although these data are in no way quantitative, it is clear that a pulse of sedimentation following the spring bloom occurs in late April. Also conspicuous is the increase in bulk and duration of sedimentation in the deeper traps. The weather conditions during the cruise were relatively good, so 4 sediment sampling at depths of 4805 m (the IOS-station in the Porcupine Sea Bight), 4471 m (close to the basis of Goban Spur), 2269 m and 1535 m (slope of Goban Spur) were possible. Generally, the found activity rates accorded to the range, which could be expected from our former measurements on VA 137. The rates were lower than on more shallow situated sampling sites (a detailed comparison of data is not possible in the moment, because the value are not exactly corrected on volume basis). Unusual high activity of protease and esterase (higher than at 1535 m) were found at 4471 m, which indicates that the basis of the continental margin acts as an accumulation zone for organic matter. Counting of bacterial abundance and must be performed later in the home laboratory. ~ CARBON MINERALIZATION BY THE BENTHIC COMMUNITY (IHF, T. Soltwedel, Geomar, O. Pfannkuche) Recent results from the temperate northeast Atlantic exhibited a strong seasonality in phytoplankton production and subsequently a varying supply of phyto-detritus to the benthos (Pfannkuche, 1993). Thus, benthic activity and biomass is subject to spatial and seasonal variations in response to the sedimentation of particulate organic matter. RV METEOR' cruise 30, leg 1 was part of a series of expeditions to survey the reaction of the benthic community to episodic (seasonal) food pulses and to assess the role of the benthic organisms for the carbon flux through the sediment. Benthic sampling was carried out along a depth transect across the Goban Spur continental margin from the outer Celtic Sea to the adjacent deep-sea basin, the Porcupine Abyssal Plain (Fig. 1 ). A total of eight stations with water depths ranging from 200 m to 4800 m were sampled with a modified SMBA style multiple corer (MC). To estimate the input of phytodetritus to the benthic community, we analysed chlorophyll/pheophytin concentrations within the sediments. Changes in activity and biomass of the benthic infauna was assessed by measuring a series of biochemical assays: activity parameters: -esterases with fluorescein-di-acetat, FDA -adenosintriphosphate, ATP biomass parameters: -total adenylates, ATP+ADP+AMP -desoxyribonucleinacid, DNA -phospholipids -particulate proteins Additionally, samples were taken for grain size analyses and to determine the sediment water content (porosity). Our investigations restrict to the upper 10 cm of the sediments. First results (Fig. 6) demonstrated the close relationship between food supply and benthic activity. Concentrations of sediment-bound chloroplastic pigments (indicating primary organic matter) and enzymatic activity (fluorescein-di- acetat turnover, FDA) showed a fairly similar pattern along the Goban Spur transect, with increasing values on the upper slope (1150 m, MC 31) and on the Pendragon Escarpment (3666 m, MC 27). So far, no explanation could be given for the unexpected high FDA values in 4500 m water depth (MC 26) while CPE values were lowest on that particular station. Results from other biochemical analyses might probably help to explain this discrepancy. To assess the carbon flux through the sediment, measurements of in situ community respiration rates were planned using a new benthic lander system. Unfortunately the central command unit of the benthic chamber could not be activated caused by a leakage of the pressure cylinder. For time reasons a second mooring of the system was not possible. Fig. (6) Chloroplastic pigments and heterotrophic activity within the uppermost centimetre of the sediments 5.2 WOCE PROGRAMMES: 5.2.1 PHYSICAL AND CHEMICAL OCEANOGRAPHY ON LEG M30/2 OPERATIONAL DETAILS (BSH, K.P. Koltermann, K.C. Soetje, IORAS, V. Terechtchenkov) Following the WOCE Hydrographic Programme requirements, the section WHP-A2 along nominally 48° has been worked as part of the One-Time Survey. In addition to the classical hydrographic parameters, nutrients, small and large volume tracer concentrations have been determined. Continuous ADCP (Acoustic Doppler Current Profiler) data provide the absolute vertical current shear of the top 500 m to calculate, from geostrophic transports, the absolute transport through this section. With a horizontal station spacing between 5 and 30 nm, a 24 x 10 l - rosette system was deployed to collect at up to 36 discreet depth levels water samples together with the quasi-continuous profiles of T, P, S and O2 with a CTDO2-probe. The track and station spacing essentially follows the Gauss section from 1993, covering, due to bad weather, 53 stations. Additional stations for performance tests of the CTD/rosette system, calibrations and for the instruments for the chemical analyses have been worked weekly. A distribution of the water samples along the section WHP-A2 is given in Fig. (7a). CTD-ROSETTE EQUIPMENT AND PROCEDURES (BSH, K.P. Koltermann, P. Wöckel) The first few stations had to be used to find the most reliable and appropriate combination of CTD, rosette pylon and trip electronics and GO-bottle set. Problems were encountered with a rosette underwater unit that did not release properly and safely at pressures higher than 2600 dbar. To economize on ship time and allow for the time required to draw water samples properly from the shallow and deep rosette, a sequence of rosette deployments was tested where the first rosette/CTD was run deep, followed if required by the LVS casts. This was followed by a shallow rosette/CTD to provide close sample spacing in the top 1500 m. First, this second rosette was then deployed on the first, that is deep cast of the following station to avoid changing the rosette and CTD connections to the wire. This was abandoned rather early in the cruise in order to run all deep casts with the best CTD/rosette combination available, and deploy the shallow cast with the priority for water samples and ensuing trip CTD data only. This sequence has provided a much more secure calibration procedure and calibration data set for the full-depth CTD data, as in essence it will not be necessary to match data from two different CTD units for this section. For the deep casts the CTD Neil Brown MkIII, labelled DHI1, was used on pylon no.7 with 24 x 10 l GO bottles uniquely marked. The shallow cast was run with the Neill Brown MkIII, labelled NB3 of IfM Kiel, with the Kiel pylon and 24 x 10 l GO-bottles. All bottles were equipped with stainless steel springs with grease-free O-rings to avoid contamination for CFC-sampling. The station routine was maintained throughout the cruise. Only few mistrips occurred and were accommodated for by standard oceanographic procedures. In heavy weather and seas, particularly at the end of the cruise, on a few stations heavy wire wear was observed ca. 20 - 50 m above the rosette. This was seen as a result of the rosette package starting to kite. Extra weight was added to the package and the lowering speed decreased slightly to 1 m/s. No more problems occurred afterwards. The acquisition software showed some mysterious problems at the beginning of the cruise where the acquisition at depth stopped and the system could not be restarted again. A simple software problem was solved after being identified. More details of the sampling procedures are given in 5.2.3. The CTD- calibration coefficients for the M30/2 leg are essentially identical to those for M30/3. Both data sets have been processed similarly. Bottle data files for both leg are, again, processed according to the WHP guide-lines and with consistent meta-data file documentation. The statistics of water bottle samples for the four calibration stations worked during M30/2 are given in Tab. 5.2.1.1. BIO SAMPLE CODING (BSH, K.P. Koltermann) On this cruise we used for both WOCE legs a sample labelling system introduced by the Bedford Institute of Oceanography, Canada. A uniquely numbered label is assigned to each water sampler at the rosette on each individual cast. The same number is assigned also to all subsamples of this particular sample bottle. Records of all groups analysing water samples maintain this unique number within their procedures until the hydrocast file is collated and merged with the trip data from the CTD of that cast. The uniquely identified sample can be traced back to the particular container/bottle of the cast it originates from. If mistrips have to be accommodated later, or sampling trip depths change due to recalibration of the pressure sensor, the sample is still tied to that volume of water/rosette bottle it was sampled from. Sampling depth was thus removed from being a sample identifier, and would later on be substituted as a parameter of the sample. Almost all groups had not been familiar with this procedure prior to the cruise. They happily adopted it after only the first station. The CTD watch was particularly pleased with it as they were relieved of frequent curious questions as to what sampling depth the sample was supposed to come from. TABLE 5.2.1.1: PRECISION OF DUPLICATE SAMPLES (I.E. FROM DIFFERENT ROSETTE BOTTLES FIRED AT THE SAME NOMINAL DEPTH) OF CALIBRATION STATIONS ON WHP-A2. STAT. #43601 STAT. #43603 STAT. #45301 STAT. #47601 Duplicates: N = 7 N = 24 N = 24 N = 24 Parameter mean±sdv mean±sdv mean±sdv mean±sdv Pctd/db 3237.96 +1.52 3201.46±0.27 4304.18±2.1 3301.73±0.87 (Pdsrt) none none none 3304.25±2.96 p/db - 2.52 Tctd/mK 2.7192±.000 42.7410±.0019 2.5769±.0003 2.5766±0.0005 (Tdsrt) none none none 2.5807±0.0044 Delta-T .0041 Sctd 34.9335±.0005 34.9284±.0004 34.9049±.0004 34.9200±0.0003 Sali 34.9318±.0003 34.9332±.0008 34.9120±.0004 34.9185±0.0004 Delta-S - .0017 .0048 .0071 -.0015 Oxygen (µmol/l) 251.99±.942 251.90±.694 249.87±.591 284.27±.472 Nitrate (µmol/l) 22.001±.083 none 22.507±.0079 16.992±0.045 Phosphate (µmol/l) 1.561±.011 none 1.581±.0026 1.159 ±0.014 Silicate (µmol/l) 36.324±.159 none 41.709±.314 19.541±0.133 THERMOSALINOGRAPH (BSH, M. Stolley; IORAS, V. Terechtchenkov) An Ocean Sensors OS200 thermosalinograph was mounted to the ship´s laboratory sea water pumping system. The data together with position and additional temperature data were logged at 1' intervals. Except for a few periods in heavy weather where air was caught in the system, the data are of good quality. Salinity samples were taken on each watch; the stability of the conductivity sensors and their statistics are promising. ADCP (BSH, M.Stolley) The shipboard ADCP system with a RD unit was run throughout the cruise. Serious data quality problems occurred during heavy weather because of air being trapped under the ship. Data were recorded at 6 min intervals, a total of 6145 profiles down to 500 m depth was archived. From Oct 22 through 27 and between 21°W and 30°W computer problems impeded the data quality. During a gale on Oct 19, 1994 one transducer of the ADCP seems to have been damaged resulting in a reduced signal to noise ratio. The data from a new Ashtech 3D GPS system could not be successfully merged with the ADCP data stream. For the leg M30/3 new software was available only in St John's. For M30/2 the normal shipboard GPS data were logged with the ADCP data stream. All data are being processed at the level previously developed for M18. ~ DETERMINATION OF THE MERIDIONAL TRANSPORTS OF HEAT, SALT AND FRESHWATER AT 48°N IN THE NORTH ATLANTIC ALONG THE WHP SECTION A2 (BSH, K.P. Koltermann, A. Sy; IORAS, V. Terechtchenkov) PRELIMINARY RESULTS The 48°N section was sampled for the fourth time since 1957. It was an exact repeat of the 1993 sampling with RV Gauss. By now we have a very clear picture of the main hydrographic features and spatial scales on this section, such as the deep boundary current regimes on both sides of the Mid-Atlantic Ridge (MAR), the spatial scales of the westward propagating Mediterranean Outflow and the eastward propagation of the Labrador Sea Water (Fig. 7 b-e). The cooling of the LSW and deepening of the LSW core layer that was previously seen during 1993 (Koltermann and Sy, 1994) has continued during the autumn of 1994. But it now is seen more prominently also in the Eastern Basin of the North Atlantic. The LSW core temperatures had changed in 1993 since the 1982 occupation of this section by CCS Hudson by -0.45°C. The core layer had deepened in that same period by 641 dbar. From summer 1993 to autumn 1994 the temperature west of the MAR had cooled by another 0.057°C and deepened further by 27 dbar. From 1982 to 1993 the LSW core temperature east of the MAR at ca. 27°W had decreased by -0.154°C; in just over one year from 1993 to 1994 it cooled by another 0.096°C, deepening by ca. 152 dbar. Salinity changes in the Western Basin are small, order 0.001, compared to the temperature changes. The effect on the density is ca.0.045 kg/m3 in the Western and 0.005 kg/m3 in the Eastern Basin manifested in the increase in depth (Fig. 8 a-d). All this clearly shows how the LSW formed in the Labrador Sea in larger quantities since the late 1980s (Lazier, 1995) now invades the Eastern Basin (see also 5.2.3). Fig. (7a) Distribution of water samples along section WHP-A2 Fig. (7b) Salinity distribution from bottle samples along WHP-A2 Fig. (7c) Potential temperature along WHP-A2 Fig. (7d) Density sigma-theta distribution along WHP-A2 Fig. (7e) Density sigma-2 (reference 2000 dbar) distribution along section WHP-A2 A feature not observed in that prominence on earlier cruises along A2/AR19 is the low surface salinity at #483, 42°26.5'W. This drop in salinity coincided with a drop in temperature by ca. 5°C. Only at 500 m depth both salinity and temperature level out to values comparable to neighbouring CTD stations. As this drop was already noticed in the thermosalinograph records approaching the station, closely spaced XBT-drops have resolved the temperature structure of an extensive eddy of northern origin on both sides of station 483. The effects of this eddy can be traced down to 2500 m in the density fields (Fig. 7d,e). CCS Hudson had surveyed the area only days earlier and had located the centre of this quasi-stationary feature, dubbed the "Mann Eddy", at 41°46'N and 44°10'W. Long-term changes in the characteristics of the Labrador Sea Water LSW for the three comparable manifestations of this section along ca. 48°N are summarised in Fig. (8 a-d). All three cruises follow an identical track east of the Mid- Atlantic Ridge MAR, only in the Western Basin the tracks of Gauss 226 in 1993 and Meteor M30/2 in 1994 are identical. For CCS Hudson the track was chosen to follow 48°N exactly, crossing Flemish Cap and its local circulation regime. An indication of the heat and salt available at 48°N and their changes since 1957, the year of the Discovery section during IGY, gives Fig. (8e,f). All available data have been interpolated on the same grid across the section. The Discovery and Hudson sections have been, for the Western Basin, projected onto the new track of the Gauss and Meteor sections. For each grid column potential temperatures and salinities have been averaged. The mean values are plotted against longitude west, and the bottom topography of the section has been included. For the continental shelf slope regions on both sides of the section the mean values are biased by the considerably shallower depths, not to be discussed here. From these figures it becomes obvious that outside the continental slope regimes the Eastern and Western basins show individual features. The Eastern Basin is much smoother, quieter at no distinct spatial scales below the basin scale. The MAR clearly separates both basins. Variations in the West show distinct spatial scales, order 300 km and much greater variability than in the East. The Labrador Current on the shelf break and the Deep Western Boundary Currents on the continental slope are seen in the general decrease in temperature and salinity west of 44°W. Fig. (8a,b) Potential temperature (8a) and depth (8b) of the Labrador Sea Water core along 48 °N for 1982, 1993 and 1994 Fig. (8c,d) Salinity (8c) and density (8d) of the Labrador Sea Water core along 48°N for 1982, 1993 and 1994 Fig. (8e,f) Depth-averaged potential temperatures (top) and salinities (bottom) along 48°N for 1957-1994 In the deep ocean we note the smooth curves in the Eastern Basin. For 1957 (Discovery) we find here the highest, for 1982 (Hudson) the lowest temperatures. The most recent survey in 1994 (Meteor) gives the lowest salinities, for 1957 with Discovery the highest. Disregarding potential accuracy questions with the Discovery salinities, we find that in 1982 and 1993 the mean salinities are almost the same, indicating that the cooling of the LSW we have observed already in the Western Basin has now progressed into the Eastern Basin. Across the MAR the boundary currents on both sides leave their imprint by coherent changes towards higher or lower values at a given location. West of the MAR up to the Milne Seamounts at 39°W for 1993 and 1994 we find the highest mean temperatures and salinities, for 1957 and 1982 the coldest and freshest water. This tendency continues into the Western Basin proper, that is West of the Milne Seamounts. Here the warming between 1957/1982 and 1993/1994 amounts to about 1°C, and the salinity increase to ca. 0.2. Despite the considerable input of newly formed at great depth, the net vertically averaged property changes are towards higher temperatures and salinities. ~ NUTRIENTS MEASUREMENTS FOR FINE RESOLUTION OF OCEANIC WATER MASSES ON THE METEOR CRUISE M30/2 (SECTION WHP-A2) IN THE NORTH ATLANTIC (IfMK, L. Mintrop, H. Johannsen, F. Malien) Nutrient analyses as well as determinations of dissolved oxygen were carried out according to the WOCE WHP standards from the samples obtained from all hydrocasts. By sampling from every successfully closed bottle, a total number of 1692 and 1737 samples were analysed for nutrients (nitrate, phosphate, silicate) and dissolved oxygen, respectively, by the nutrient team from the Institute of Marine Sciences, Marine Chemistry Department, Kiel, Germany. The quality of the data was assured by carrying out the quality and reproducibility checks according to the WOCE standard operation procedures. These parameters were also measured from the samples (a total of 138) obtained with the large volume samplers of the C-14 group. The data from the measurements were made available to the participants at the end of the cruise to help in the fine resolution of oceanic water masses in the North Atlantic. Besides this goal, nutrient and oxygen distributions, especially in the upper water column, allow the interpretation of seasonal biological processes and therefore contribute to the CO2-studies of this cruise. The data are summarised in the Fig. (9 a-d). Fig. (9a) Distribution of dissolved oxygen along section WHP-A2 Fig. (9b-c) Distributions of silicate (8b), nitrate (8c) along section WHP-A2 Fig. (9d) Distribution of phosphate along section WHP-A2 ~ CFCS ON THE WHP SECTION A2 (IUP-B, W. Roether, A. Putzka, K. Bulsiewicz, C. Rüth, H. Rose) OPERATIONAL DETAILS The CFC analyses are performed onboard. Except for shallower areas almost each station was sampled at up to 36 levels. The CFC samples were drawn from 10 liter Niskin bottles on large glass syringes. During sampling the contamination with ambient CFC had to be avoided and controlled. In all 1062 analyses for F11, F12, F113 and 978 analyses for CCl4 have been performed, and the data were evaluated preliminary at sea. The investigated tracers are the man-made chlorofluorocarbons (CFC) F11, F12, F113 and carbon tetrachloride CCl4. Their time-dependent input at the ocean surface is known. The tracer concentration of the surface water is altered by mixing processes when the water descends to deeper levels of the ocean. Measuring the concentration of the tracers delivers information about time scales of ventilation processes of subsurface water. The atmospheric F11 and F12 contents increase monotonously with different rates since the forties. CCl4 increases since 1920 while F113 started to increase in 1970. Hence the concentration ratios of the different tracers vary over wide time ranges and can be used to indicate the 'age' of water masses (age since leaving the surface). 'Younger' water is tagged with higher CFC concentration compared with 'older' water. SAMPLING Samples were taken according to the WOCE scheme. CFCs: glass syringes, on 45 of 53 hydrographic stations 1048 samples were taken and measured on board. HELIUM: 80 helium samples in copper tubes for on shore extraction, intercalibration purposes. Samples to be measured on shore. MEASUREMENTS: All CFC measurements were done using a gas-chromatographic system especially improved because of problems with the analysis of F113 (chromatographic interference with CH3I). The system is now equipped with a new designed micro- trap for collecting the different gases purged from a water sample, a special pre-column to improve especially the resolution between CH3I and F113 and a electronic pressure regulator for a better baseline stability. Due to these changes we were able to measure F113 with sufficient chromatographic resolution and to produce for the first time a high quality set of measurements for the whole section. Fig. (10) F113 (upper part) and CCl4 distribution on A2. Values given in ppt. PRELIMINARY RESULTS In Fig. (10) sections for F113 and CCl4 are shown. Within the eastern basin of the section the lowest F113 and CCl4 values were found below about 3500 m indicating as expected the oldest water found on the section. For the deep western basin a layer of water with higher F113 concentration is found at the bottom due to the recently ventilated overflow water from the Denmark Strait. Lower concentrations were observed at a depth range between 3000 and 4000m on the western flank of the Mid Atlantic Ridge. This indicates most probable a re- circulating portion of a mid depth North Atlantic Deep Water (NADW). Most significant is a layer with higher F113 and CCl4 concentrations indicating the Labrador Sea Water (LSW) at about 1900m depth which extends over the whole North Atlantic. The Mediterranean Overflow Water (MOW) shows up slightly above 1000m depth at the eastern side of the West European basin. While the F113 and also F11 and F12 (not shown here) is here lower, the CCl4 shows a much clearer minimum. It is known that CCl4 degrades but only within water warmer than about 10-12°C. The original overflowing Mediterranean Water is above that temperature and therefore the MOW found in the Atlantic has significant lower concentration in CCl4 compared to Atlantic waters of comparable temperature or comparable concentration of the other CFCs. ~ TRITIUM/HELIUM AND 14C-SAMPLING ALONG WHP-SECTIONS A2 AND A1 (IUP-HD, R. Bayer, B. Kromer, M. Born) The experimental goal of the cruise was the collection and measurement of a representative data set of geochemical tracers along the WHP section A2. The data will be used to determine mixing rates and apparent ages of the water masses in the North Atlantic. A special focus is on the deep boundary currents along the continental margins and the Mid Atlantic Ridge. Sampling and interpretation will be done in close cooperation with all groups involved. The transient tracer data obtained will be compared with the 1972 GEOSECS data and the TTO/NAS data from 1980/81 in the Northern Atlantic. From the evaluation of the tracer fields further indications will be obtained how much and how fast the invasion of the tracer signals from the surface into the deep waters has proceeded. The sampling programme was split into two components: small volume samples for analyses of the CFCs, helium isotopes, tritium and AMS-14C to be collected with the rosette system, and a C-14 programme using large volume samplers. During M30/2 468 tritium samples have been collected. About 1 liter of water is sampled in glass bottles for determination of the tritium concentration. In the home laboratory from a certain amount of water the helium is degassed quantitatively and the sample is stored in a vacuum container for several months. During that time tritium decays and the decay product, 3He, is enriched. The latter will be detected with a special high sensitivity, high resolution mass spectrometer. For helium measurement ca. 40 cc of sea water are sampled in a copper tube sealed with pinch-off clamps. Analyses will be performed on-shore with a dedicated helium isotope mass spectrometer after extraction of the helium dissolved in the water. A total of 474 samples were collected. In addition samples have been taken to test a seagoing helium extraction system. In all 311 samples were taken both parallel and supplementary to the conventional sampling procedure. All samples have been processed onboard, and the measurements have been done in the home laboratory after the cruise. The duplicate samples obtained in copper containers as well as several seagoing replicate samples will be used to assess the performance of the new system. Furthermore 60 AMS-14C samples have been drawn from the rosette. This programme is supplementary to the large volume 14C sampling and was restricted mainly to the upper water column. For the large volume sampling ten Gerard-Ewing bottles with a volume of 270 liter each are used. The bottles are run in vertical series in two casts at the relevant stations. The shallow cast was followed by a CTD/rosette cast to give time to the onboard 14C-extraction and the subsequent preparation of the large volume samplers for the deep 14C-cast. For the M30/2 section 8 large volume stations with a total of 204 14C samples have been worked. PRELIMINARY RESULTS As a first example of the data from this cruise Fig. (11) shows selected profiles of tritium concentrations in the Western Basin. West of the MAR one can distinguish clearly separated depth ranges. For the LSW depth range we find tritium values of 1.2 -1.4 TU. Deeper, the distribution is more homogeneous, particularly in the central basin with a mean concentration of ca 0.75 TU. On the WHP-A1 section further north during leg M30/3 we find for these water masses significantly higher concentrations. We intend to use a multi-tracer approach to determine the mixing ratios and spreading rates for these water masses. We will also estimate the mean renewal times for the individual depth ranges. Fig. (11) Selected tritium profiles for the Western Basin on section A2 5.2.2 MOORING RECOVERY ON WHP- A2 AND WHP-A1 (BSH, K.P. Koltermann and IfMHH, J. Meincke) During the Gauss cruise no 226 in the summer of 1993 three moorings were deployed west of the Mid Atlantic Ridge on the WOCE section A2 to measure the fluctuations and spatial extent of a deep salinity maximum. These moorings could not be turned around in the summer of 1994 and thus a recovery was planned as part of this cruise. Two of the three moorings could be interrogated acoustically, one failed to answer. An attempt to dredge for the mooring K1 in a weather lull was not successful. Weather changes prevented other attempts to recover these moorings. In summer 1995 the mooring K3 was completely and the mooring K1 partially recovered from RV Gauss by dredging. The mooring K2 could not recovered. From K3 some 640 days of data are now available. The recovery attempts for the mooring D2 on leg M30/3 by dredging was not successful. Further attempts for dredging operations for other moorings had to be cancelled because of the prevailing weather and time constraints. 5.2.3 PHYSICAL, CHEMICAL AND TRACER OCEANOGRAPHY ON LEG M30/3 HYDROGRAPHIC MEASUREMENTS ON WHP-A1 (BSH, A. Sy) Hydrographic casts were carried out with a NBIS MK-IIIB CTDO2 unit (internal name: "DHI-1") mounted on a GO rosette frame with 24 x 10 litre Niskin bottles and owned by BSH. The mean constant maximum descent rate was 1 m/s. CTDO2 data were collected at a rate of 64 ms/cycle using a PC based (HP Vectra 486) data acquisition software (CZHEAD rev. 18) designed by BSH. A video tape unit was used as a backup system on each cast. Hardware and software instrumentation ran without serious problems during the whole cruise leg. The rosette system used proved to be well adapted to the CTD unit, and thus only few tripping failures encountered. Both pressure and temperature (ITS90) were calibrated before (Sept./Oct. 1994) and after the cruise (February 1995) by the calibration facilities at IfM Kiel. The post cruise pressure calibration needed to be repeated in November 1995 due to uncertainties with results from the February calibration. Salinity was calibrated by comparison of CTD with sample salinities. 24 SIS digital temperature meters (RTM 4002) and 7 SIS digital pressure meters (RPM 6000), calibrated by the manufacturer in October 1994, were used in a rotating mode throughout this cruise leg to control the CTD sensors' stability. DSRT readings, along with salinity, oxygen and chemical data from the rosette water samples, were also used to detect erroneous depths of bottle firings. Unfortunately, 7 DSRTs were destroyed at the ship's side by heavy sea. The bottle sampling sequence was as follows. Oxygen samples were collected soon after the CTD system was brought on board and after CFC and 3He were drawn. The sample water temperature was measured immediately after the oxygen sample was drawn. The next samples drawn were TCO2, 14C, 3H, nutrients (NO2 + NO3, SIO3, PO4), and salinity. All bottle samples taken were linked to the rosette Niskin bottles by the "Bedford" sample identification system (see 5.2.1). Salinity samples were drawn into dry 200 ml BSH salinity bottles with polyethylene stoppers and external thread screw caps. It was found by Kirkwood and Folkard (1986) that these bottles guarantee best long-term storage conditions, a problem encountered with the old soft glass seawater sample bottles (Sy and Hinrichsen, 1986). Bottles were rinsed three times before filling. Samples were collected as pairs of replicates (i.e. two samples from the same rosette bottle), one for shipboard salinity measurements and one for backup purposes, e.g. for the possibility of cross checks by later shore-based salinity analysis. The rosette sampling procedure was completed by readings of electronic DSRTs for a first quick check of the scheduled bottle pressure level and for in-situ control of the CTD pressure and temperature calibration. In all 18 CTDO2-rosette stations were occupied along section A1/West and 45 CTDO2-rosette stations along section A1/East (Fig. 12a, List 7.1.3), of which the first two casts at station # 489 were used to test winch, cable, two CTD- rosette systems as well as the sampling procedure and the laboratory equipment. Three casts were used for rosette sample quality tests at stat. # 496, 517 and 542 by means of multi-trips at the same depth level (Table 5.2.3.1). An overview of the locations of water samples is given in Fig. (16 a). Activities, occurrences and measured parameters are summarised in the station listing (List 7.1.3). Fig. (12a) Positions of CTDO2/rosette stations for R.V. "Meteor" cruise no. M30/3 Fig. (12) CTD-sections A1/West, (b) potential temperature (°C), (c) salinity, (d) density (sigma-t) To meet WOCE quality requirements, the processing and quality control of CTD and bottle data followed the published guidelines of the WOCE Operations Manual (WHPO 91-1) as far as their realisation was technically possible on this cruise. Standard CTD data processing and bottle data quality control (including oxygen and nutrient samples) were carried out on board during the cruise using BSH designed software tools. The final CTD data processing was done in the laboratory at BSH and included the application of corrections to pressure, temperature and salinity and the oxygen calibration. Property sections from CTD data are presented in Fig. (12b-d). CTD data processing and quality evaluation will be discussed in greater detail in a separate data report. All hydrographic data are submitted for independent quality evaluation to the WOCE Hydrographic Programme Office. The ADCP was serviced during the St. John's stopover. The antenna configuration of the new Ashtech GPS-system was re-initialised there. Measurements started on Nov. 15,1 1994 and had to be discontinued on Nov 28, 1994 in the Irminger Sea due to total collapse of the system due to transducer flooding in heavy weather. The third transducer had already failed on Nov 18, 1994. In all 2983 velocity profiles at 6 min intervals have been recorded are being processed with standard methods. TABLE 5.2.3.1: PRECISION OF DUPLICATE SAMPLES (I.E. FROM DIFFERENT ROSETTE BOTTLES FIRED AT THE SAME NOMINAL DEPTH) OF ROSETTE TEST STATIONS. STAT. #496 STAT. #517*) STAT. #542 Duplicates: N = 19 N = 16 N =11 Parameter mean±sdv mean±sdv mean±sdv Pctd/db 1473.7±5.7 1401.4±1.2 3948.5±4.0 (Pdsrt) 1471.9 1402.0±3.5 none Tctd/mK 2.8125±.0013 3.0466±.0100 2.4761±.0007 (Tdsrt) 2.8177±.0028 3.0542±.0077 none Delta-T .0054±.0027 .0045±.00240 none Sctd 34.8332±.0011 34.8621±.0012 34.9070±.0002 Sali 34.8320±.0004 34.8617±.0014 34.9050±.0003 Delta-S -.0013±.0004 -.0004±.0007 Oxygen 6.9125±.0043 6.8764±.0124 5.5216±.0039 (ml/l) (.06 % fs) (.18 %) (.07 %) Nitrate 16.876±.061 17.217±.068 23.507±.0128 (µmol/l) (.36 % fs) (.39 %) (.54 %) Phosphate 1.0982±.0035 1.0982±.0082 1.5810±.0068 (µmol/l) (.32 % fs) (.75 %) (.43 %) Silicate 9.371±.043 9.746±.026 45.110±.056 (µmol/l) (.46 % fs) (.27 %) (.12 %) *) Water mass not as homogeneous as desired It turned out that the pre- and post-cruise laboratory calibrations of pressure and temperature were stable (no significant differences) and thus these functions were used for the final correction of the field data (Fig. 13, Tab. 5.2.3.2). Fig. (13) Pre- and post -cruise calibration (a) Pressure at T = 10°C (Oct 94) (b) Pressure at T = 1.6°C (Oct 94) (c) Pressure at T = 8-9°C (Nov 95) Fig. (13d) Pre- and post -cruise calibration, Temperature The salinity correction was carried out by means of in-situ data. After pressure and temperature corrections were applied and salinity recalculated, the remaining salinity error consists of a small temporal drift only (Fig. 14). For salinity analysis of samples a standard Guildline Autosal salinometer model 8400 (s/n 56414) was used on board together with the processing software (SOFTSAL with ATS rev. 1.3 and ATSPP rev. 2.1) designed by SIS. One ampoule of IAPSO Standard Seawater (batch P 124) was used per 2 stations (48 samples). The instrument was operated in the ship's constant temperature laboratory at a bath temperature of 24°C with the laboratory temperature set to 23°C. Salinity was measured about 2 days after water collection. No backup seawater sample analysis was needed to be carried out. Oxygen sample measurements were carried out by BSH technicians (see 5.2.3.4). Because CTD oxygen sensors cannot be calibrated satisfactorily in the laboratory, field calibration is the only alternative. This procedure was carried out in line with the guidelines given by Millard (1993) by merging the down-profile CTD data with corresponding up-profile water samples. Oxygen residuals of the final fit versus stations are shown in Fig. (15). Fig. (14a) Salinity residuals, versus CTD salinity, M30/3 Fig. (14b) Salinity residuals, versus CTD stations, M30/3 Fig. (15) Oxygen residuals of final fit versus CTD stations TABLE 5.2.3.2: LABORATORY CALIBRATION COEFFICIENTS FOR CTD "DHI-1" TEMPERATURE AND PRESSURE CORRECTION POLYNOM PCORR, TCORR (E.G. TNEW = TOLD + TCORR) Temperature Pressure Pressure (downcast) (upcast) a0 0.0010 -1.68 -2.31 a1 -0.000508 0.0140268 -0.001693 a2 9.3139 E-6 -2.14633 E-5 1.10129 E-6 a3 1.24996 E-8 -6.08444 E-11 a4 -3.39917 E-12 -1.21793 E-14 a5 4.39732 E-16 a6 -2.19759 E-20 Note: The a0-coefficients for pressure are caused by the lab calibration procedure only and are not used for pressure correction. The actual pressure offset protocolled for each station is used as a0. NUTRIENTS ALONG WHP-A1 (BSH, A. Sy, MAFF. D. Kirkwood) Along the entire two part of WHP-A1 concentrations of dissolved oxygen and nutrients have been analyzed from water samples. Details of the analyses and methods are given in 5.2.3.4 and 5.2.3.5, respectively. In Fig. (16a-e) we display the distribution of the sample positions and the data. Fig. (16a) Distribution of water samples along WHP-A1 Fig (16b) Distribution of the concentrations of dissolved oxygen along WHP-A1 Fig (16c) Distribution of the concentrations of silicate (16c) along WHP-A1 Fig. (16d-e) Distribution of nitrate (16d) and phosphate (16e) along WHP-A1 SPREADING OF NEWLY FORMED LABRADOR SEA WATER (BSH, A. Sy) A