Arctic pacing of North Atlantic climate variability through freshwater exports

Abstract

<p>Freshwater plays a key role in the Arctic - North Atlantic climate system, linking ice, ocean and atmospheric dynamics. In particular, large freshwater releases into the subpolar region drive extreme cold anomalies, create sharp sea surface temperature fronts, destabilise the overlying atmosphere, and trigger shifts in major ocean currents. Considering the expected increased freshwater fluxes in future due to more melt, it is critical to understand the resulting climate feedbacks.</p><p>Combining observations and models, we present evidence that past changes in Arctic freshwater outflow paced transitions between North Atlantic cold and warm anomalies. This circulation-driven freshwater cycle explained over 50% of the sea surface temperature variability in the subpolar North Atlantic and was particularly pronounced on decadal timescales. However, new findings indicate that the recent freshwater input due to more melting has increased the amplitude and frequency of freshwater variations in the North Atlantic, leading to a shift of power in the North Atlantic climate variability from decadal to interannual timescales. In addition, the interference of the circulation-driven freshwater cycle by melting has contributed to the storage of freshwater in the Arctic Ocean, where it now poses the possible risk of rapid climate change if the freshwater were released. In light of newly identified, Arctic feedbacks to melt-driven freshwater events in the North Atlantic, we suggest that an Arctic freshwater release is becoming increasingly likely.</p>