An Investigation of Gas Exchange and Water Circulation in the Amundsen Sea Based On Dissolved Inorganic Radiocarbon

We used radiocarbon isotope ratios in dissolved inorganic carbon to assess gas exchange and water circulation in the western Amundsen Sea. Radiocarbon isotope ratios indicate that Circumpolar Deep Water enters the basin along the seafloor and that the upper layer is formed through modification of this water mass. In the Amundsen Sea Polynya, radiocarbon isotope ratios of surface water are higher than those of underlying Winter Water, implying rapid absorption of atmospheric CO₂. A CO₂ absorption rate of 45 mmol m⁻² d⁻¹ calculated for a site in the central polynya is higher than that near the Dotson Ice Shelf (28 mmol m⁻² d⁻¹). The turnover time of water in the Dotson Trough region of the western Amundsen Sea is estimated to be 10–30 years, based on results from a box model and radiocarbon mass balance.