New research reveals the importance of winter sea ice in the year-to-year variability of the amount of atmospheric CO₂ absorbed by a region of the Southern Ocean.

In years when sea ice lasts longer in winter, the ocean will overall absorb 20% more CO₂ from the atmosphere than in years when sea ice forms late or disappears early. This is because sea ice protects the ocean from strong winter winds that drive mixing between the surface of the ocean and its deeper, carbon-rich layers.

The findings, based on data collected in a coastal system along the west Antarctic Peninsula, show that what happens in winter is crucial in explaining this variability in CO₂ uptake.

A new study led by Michael Mann of the University of Pennsylvania finds that atmospheric patterns known to lock in extreme weather, like heat domes and flooding, have nearly tripled since the 1950s. The research highlights a growing gap between real-world risks and what climate models currently capture.