Sea ice suppression of CO2 outgassing in the West Antarctic Peninsula: implications for the evolving Southern Ocean carbon sink

The Southern Ocean plays an important role in the uptake of atmospheric CO₂. In seasonally ice-covered regions, estimates of air-sea exchange remain uncertain in part because of a lack of observations outside the summer season. Here we present new estimates of air-sea CO₂ flux in the West Antarctic Peninsula (WAP) from an autonomous mooring on the continental shelf. In summer, the WAP is a sink for atmospheric CO₂ followed by a slow return to atmospheric equilibrium in autumn and winter. Outgassing is almost entirely suppressed by ice cover from June through October, resulting in a modest net annual CO₂ sink. Model projections indicate sea ice formation will occur later in the season in the coming decades potentially weakening the net oceanic CO₂ sink. Interannual variability in the WAP is significant, highlighting the importance of sustained observations of air-sea exchange in this rapidly changing region of the Southern Ocean.