Close coupling between seasonal biological production and dynamics of dissolved inorganic carbon in the Indian Ocean sector and the western Pacific Ocean sector of the Antarctic Ocean

The distribution of total dissolved inorganic carbon (DIC) in surface sea water and the upper water column of the seasonal ice zone in the Antarctic Ocean between 30°E and 150°E was investigated in the austral summer 1992/1993. In February–March 1993, total DIC content of surface seawater in the seasonal ice zone showed large spatial variability, ranging from 2064 to 2166 μmol kg-1. Biological activity played an important role in the deficit of total DIC in Prydz Bay, in the marginal ice zones (MIZ) near Lützow-Holm Bay and Casey Bay, and in the offshore regions near 63°S, 100°E, while the decrease in total DIC due to meltwater input from the receding sea ice was also significant in those MIZ and in the area off the West Ice Shelf. he analyses of total DIC concentration in the coldest waters (t<−1.7°C) of the subsurface temperature minimum layer, we deduced a characteristic value of normalized total DIC concentration (2184.0±3.7 μmol kg-1 at S=34) for the winter mixed layer over the wide area we investigated. Seasonally integrated net community production (NCP) in summer and its ΔCT/ΔN/ΔP ratios were calculated on the basis of the difference in normalized total DIC and nutrients concentrations between the winter mixed layer and the Summer Surface Water. Large spatial variations in the NCP, ranging from 10 to 48 gC m-2, and different ΔCT/ΔN/ΔP consumption ratios, typically 58/9.2/1 and 84/9.0/1, suggest the high variability of organic matter production and of its impact on both the air-sea CO2 exchange and export of carbon from the photic layer to the deeper waters in the seasonal ice zone of the Antarctic Ocean.