Ocean carbon cycling in the Indian Ocean: 1. Spatiotemporal variability of inorganic carbon and air‐sea CO2 gas exchange

The spatiotemporal variability of upper ocean inorganic carbon parameters and air‐sea CO2 exchange in the Indian Ocean was examined using inorganic carbon data collected as part of the World Ocean Circulation Experiment (WOCE) cruises in 1995. Multiple linear regression methods were used to interpolate and extrapolate the temporally and geographically limited inorganic carbon data set to the entire Indian Ocean basin using other climatological hydrographic and biogeochemical data. The spatiotemporal distributions of total carbon dioxide (TCO2), alkalinity, and seawater pCO2 were evaluated for the Indian Ocean and regions of interest including the Arabian Sea, Bay of Bengal, and 10°N–35°S zones. The Indian Ocean was a net source of CO2 to the atmosphere, and a net sea‐to‐air CO2 flux of +237 ± 132 Tg C yr−1 (+0.24 Pg C yr−1) was estimated. Regionally, the Arabian Sea, Bay of Bengal, and 10°N–10°S zones were perennial sources of CO2 to the atmosphere. In the 10°S–35°S zone, the CO2 sink or source status of the surface ocean shifts seasonally, although the region is a net oceanic sink of atmospheric CO2.