LAUSR

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.