A. Cruise narrative A.1. Highlights a. WOCE designation: P21E and P21W b. EXPOCODE 318MWESTW/4 318MWESTW/5 c. Chief scientist: Leg 1: Michael McCartney, WHOI Leg 2: Harry Bryden, JRC d. Ship: R/V Melville e. Ports of call: Leg 1: Iquique, Chile to Papeete, Tahiti Leg 2: Papeete to Brisbane, Australia f. Cruise dates: Leg 1: March 27 to May 15, 1994 Leg 2: May 19 to June 25, 1994 A.2. Cruise Summary Information a. Geographic boundaries: 14 30 S 154 E 74 W 25 43 S The cruise was conducted within 1deg of 17 S from 74 W to 169 E. The section then bore WSW to finish at 25 43 S 154 E. b. Stations occupied: A total of 294 CTD/rosette stations were occupied. 161 stations were occupied on Leg 4 and 133 on Leg 5. c. Floats and drifters deployed: No information yet available. d. Moorings deployed or recovered: No moorings were deployed or recovered on this cruise. A.3. List of Principal Investigators Table 1: List of Principal Investigators Measurement Principal Investigator Institution -------------------------------------------------------------- Salinity, oxygen John Toole WHOI CTD/O2 John Toole WHOI Nutrients Lou Gordon OSU Chlorofluorocarbons Rana Fine RSMAS Helium/tritium Bill Jenkins WHOI ADCP Mike Kosro OSU ALACE floats Russ Davis SIO Drifters Peter Niiler SIO TCO2 Chris Winn Univ. of Hawaii Catherine Goyet WHOI pH Frank Millero RSMAS Alkalinity Catherine Goyet WHOI Frank Millero RSMAS Underway pCO2 Catherine Goyet WHOI Meteorology David Wirth SIO Air chemistry ? ? Bathymetry Stu Smith SIO A.4. Scientific Programme and Methods The object of this cruise was to occupy a series of CTD/O2 (Conductivity- Temperature-Depth-Oxygen) stations approximately along 17degS from the continental shelf of Peru to the continental shelf of Australia, with an intermediate port stop in Tahiti. This collection of high-quality water- property data will help define the pattern of circulation in the South Pacific. At each station measurements of temperature, salinity, and dissolved-oxygen concentration were made continuously with depth, and the concentrations of dissolved silica, phosphate, nitrate, and nitrite were measured at up to 36 discrete levels. In addition, measurements of freon, tritium concentrations and CO2 weremade at selected levels. The station spacing ranged from 5 to 40 nautical miles, and all lowerings were made to within 10 20 m of the bottom. Continuous echo-sounding was maintained along the cruise track, as well as ADCP current measurements. A.5. Major Problems and Goals Not Achieved None noted. A.6. Other Incidents of Note As part of the obligations stated as a condition of research in the waters of Peru, Lieutenant Jorge Paz Acosta, Chief of the Department of Environment, Peruvian Navy, participated in the cruise from Iquique, Chile to Tahiti. He was given complete preliminary data files upon his departure from Tahiti. As part of the obligations stated as a condition of research in the waters of the Cook Islands, Mr. Benjamin E. Ponia, Acting Senior Fisheries Research Officer, participated in the cruise from Tahiti to Australia. He replaced Mr. Ian Bertram, who was originally scheduled to participate. B. Underway Measurements B.1 Navigation and bathymetry B.2 Acoustic Doppler Current Profiler (ADCP) B.3 Thermosalinograph and underway dissolved oxygen, etc B.4 XBT and XCTD B.5 Meteorological observations B.6 Atmospheric chemistry C. Hydrographic Measurements C.1 Water sample salinity and oxygen data Water samples were collected from every bottle during this cruise for the determination of salinity and dissolved oxygen. The primary purpose of these measurements is to accurately calibrate the sensors on the CTD. C.1.a. Salinity Water was collected in 8 ounce glass bottles. The bottles were rinsed twice, and then filled to the neck. After the sample reach the lab temperature of 21 deg. C, they were analyzed for salinity using a Guildline Autosal Model 8400B salinometer. The salinometer was standardized once a day using IAPSO Standard Seawater Batch P-123. Salinity readings were logged automatically to a computer, merged with the CTD data, and finally used to update the CTD calibrations. Accuracy of salinity measurements were +/- 0.001 PSU. C.1.b. Dissolved oxygen Measurements were made using a modified Winkler technique simlar to that described by Strickland and Parson (1972). Each seawater sample was collected in a 150 ml brown glass Tincture bottle. When reagents are added, iodine is liberated in amounts proportional to the dissolved oxygen in the sample. A carefully measure aliquot was collected from the prepared oxygen sample and was titrated for total iodine content. Titration was automated, using a PC controller and a Metrohm Model 665 Dosimat burette. The titration endpoint was determined amperometrically using a dual plate platinum electrode, with a standard deviation of replicate samples of 0.005. This technique is described more thoroughly by Knapp et al (1990). Calculated oxygen was merged with the CTD data, and used to update the CTD calibrations. D. Acknowledgments E. References Knapp, G.P., M.C. Stalcup and R.J. Stanley, 1990. Automated Oxygen Titration and Salinity Determination. WHOI Technical Report, WHOI-90-35, 25 pp. Strickland, J.D.H. and T.R. Parsons, 1972. The Practical Handbook of Seawater Analysis. Bulletin 167, Fisheries Research Board of Canada, 310 pp. Unesco, 1983. International Oceanographic tables. Unesco Technical Papers in Marine Science, No. 44. Unesco, 1991. Processing of Oceanographic Station Data. Unesco memorgraph By JPOTS editorial panel. F. WHPO Summary Several data files are associated with this report. They are the 318westw_4.sum and 318westw_5.sum, 318westw_4.hyd and 318westw_5.hyd, 318westw_4.csl and 318westw_5.csl and *.wct files. The *.sum file contains a summary of the location, time, type of parameters sampled, and other pertinent information regarding each hydrographic station. The *.hyd file contains the bottle data. The *.wct files are the ctd data for each station. The *.wct files are zipped into one file called 318westw_4wct.zip and 318westw_5wct.zip. The *.csl file is a listing of ctd and calculated values at standard levels. The following is a description of how the standard levels and calculated values were derived for the *.csl file: Salinity, Temperature and Pressure: These three values were smoothed from the individual CTD files over the N uniformly increasing pressure levels. using the following binomial filter- t(j) = 0.25ti(j-1) + 0.5ti(j) + 0.25ti(j+1) j=2....N-1 When a pressure level is represented in the *.csl file that is not contained within the ctd values, the value was linearly interpolated to the desired level after applying the binomial filtering. Sigma-theta(SIG-TH:KG/M3), Sigma-2 (SIG-2: KG/M3), and Sigma-4(SIG-4: KG/M3): These values are calculated using the practical salinity scale (PSS-78) and the international equation of state for seawater (EOS-80) as described in the Unesco publication 44 at reference pressures of the surface for SIG-TH; 2000 dbars for Sigma-2; and 4000 dbars for Sigma-4. Gradient Potential Temperature (GRD-PT: C/DB 10-3) is calculated as the least squares slope between two levels, where the standard level is the center of the interval. The interval being the smallest of the two differences between the standard level and the two closest values. The slope is first determined using CTD temperature and then the adiabatic lapse rate is subtracted to obtain the gradient potential temperature. Equations and Fortran routines are described in Unesco publication 44. Gradient Salinity (GRD-S: 1/DB 10-3) is calculated as the least squares slope between two levels, where the standard level is the center of the standard level and the two closes values. Equations and Fortran routines are described in Unesco publication 44. Potential Vorticity (POT-V: 1/ms 10-11) is calculated as the vertical component ignoring contributions due to relative vorticity, i.e. pv=fN2/g, where f is the coriolius parameter, N is the buoyancy frequency (data expressed as radius/sec), and g is the local acceleration of gravity. Buoyancy Frequency (B-V: cph) is calculated using the adiabatic leveling method, Fofonoff (1985) and Millard, Owens and Fofonoff (1990). Equations and Fortran routines are described in Unesco publication 44. Potential Energy (PE: J/M2: 10-5) and Dynamic Height (DYN-HT: M) are calculated by integrating from 0 to the level of interest. Equations and Fortran routines are described in Unesco publication 44. Neutral Density (GAMMA-N: KG/M3) is calculated with the program GAMMA-N (Jackett and McDougall) version 1.3 Nov. 94.