Ocean heat transport modulates Arctic sea ice loss

Decades of literature propose ocean heat transport (OHT) as a potential cause for uncertainty in the rates of Arctic sea ice loss based on strong correlations across different climate models. This study presents a simple underlying physical theory, derived from the large-scale energy budget of the polar region, that explains the impact of OHT on Arctic sea ice. Expressed in an intuitive linear equation, we show that this captures the relationship between historical and future Arctic sea ice loss, OHT, and polar warming, across 20 of the latest-generation climate models. Furthermore, using a lagged-correlation analysis, we find that changes in OHT lead the losses in sea ice, implying that OHT exerts a systematic modulation of historical and future Arctic sea ice loss. Our simple equation applies equally in the Southern hemisphere, for which Antarctic sea ice loss is also strongly correlated with the change in poleward OHT. However, here sea ice loss leads changes in the OHT, with further scrutiny of the other terms in our equation identifying changes to the atmospheric circulation as the primary driver. On the basis of these findings, we strongly advocate further research into the causes of different ocean (atmospheric) circulation changes in the Arctic (Antarctic) and better validation in climate models to ultimately reduce uncertainty in future projections.