Regional variation of spring N‐uptake and new production in the Southern Ocean

Abstract

Nitrate, ammonium and urea uptake were examined in the Southern Ocean (Australian sector) during the 2001 austral spring. On the basis of N‐uptake conditions, three regions were distinguished: (1) the Sub‐Antarctic Zone and the Sub‐Antarctic Front, (2) the Polar and Inter‐Polar Frontal Zones, and (3) the Antarctic Zone‐South and the Seasonal Ice Zone. N‐uptake was highest in region 3 and dominated by new production. Region 1 had the lowest N‐uptake, and switched from regenerated to new production between two visits approximately 1 month apart. Region 2 displayed intermediate N‐uptake and the lowest new production. This contrasts with previous study at 170°W where new production was high around the Polar Front and indicates that this area is not highly productive nor particle‐exporting at all longitudes. Overall, N‐uptake and new production were low all along the latitudinal transect compared to other areas of the Southern Ocean under spring conditions.