5a. Meridional Distribution of the Total CO2 Concentration:

The distribution of the total CO2 concentration along the WOCE sections P-16 (150.5°W), P-17 (135.0°W) and P-19 (88°W) are shown in Figs. 11, 12, and 13, respectively. The deep water data indicate that there is a CO2 maximum centered about 2600 meters deep representing a southward return flow of the Antarctic Deep Water from the North Pacific. The maximum intensifies northward and weakens southward disappearing in the vicinity of 50°S. It extends further south more to the east as illustrated by the 2270 µmol/kg contour, which is located at about 47°S along 150.5°W (Fig. 11), 49°S along 135°W (Fig. 12) and 54°S along 88°W (Fig. 13).

The distribution of the CO2 maximum observed along the 150.5°W (Fig. 11, WOCE P-16 section) weakens to the north as well as to the south as evidenced by closures of the 2300 and 2310 µmol/kg contours at both ends. On the other hand, along the 135.0°W (Fig. 12) and 88°W (Fig. 13) sections, the deep water CO2 maximum increases northward as far north as the edge of the plot. This difference appears to be due to the Tuamotu Archipelago, a topographic high, which largely blocks the southward path of the return flow from the north (Takahashi et al., 1993). Below the CO2 maximum water, the Southern Ocean waters with lower CO2 concentrations are found. These waters of the Southern Ocean which have relatively uniform TCO2 concentrations between 2250 and 2260 µmol/kg south of about 50°S appear to flow northward and mix with the overlying high-CO2 North Pacific waters thus forming negative CO2 gradients with increasing depth.

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