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. Plain Language Summary The Southern Ocean absorbs a considerable amount of carbon dioxide from the atmosphere and plays an important role in regulating climate on Earth. Ice covered regions of the Southern Ocean are difficult to access and observations are often limited to the ice-free summer season. Here we present new observations over a full 12 month period from a mooring on the continental shelf of the West Antarctic Peninsula (WAP). The observations indicate that the WAP absorbs carbon dioxide in the summer season, while the presence of sea ice in winter prevents that carbon from being released back to the atmosphere. Over the next few decades less sea ice is expected to form and this may lead to a weakening of the carbon dioxide uptake in the WAP region.

Automated summary

The Southern Ocean is a key player in absorbing atmospheric carbon dioxide, with the West Antarctic Peninsula absorbing CO2 in summer and ice cover preventing outgassing in winter. Future projections suggest that decreasing sea ice formation may weaken the region's ability to uptake carbon dioxide in the coming decades.