Stronger Variability in the Arctic Ocean Induced by Sea Ice Decline in a Warming Climate: Freshwater Storage, Dynamic Sea Level and Surface Circulation

Arctic liquid freshwater content (FWC) influences both regional and large-scale ocean dynamics and climate. In this study the responses of Arctic FWC, sea surface height (SSH) and surface circulation to different atmospheric circulation modes and the impact of sea ice decline on these responses are investigated by using wind perturbation simulations. The responses are intensified by sea ice decline through its resulting enhancement in ocean surface stress, indicating stronger decadal variability in the Arctic liquid FWC, SSH and ocean circulation in a warming climate. The Arctic Oscillation (AO) and Beaufort High (BH) wind forcing can significantly change Arctic regional and total FWC. Compared to the sea ice condition in the 1980s, the amplitudes of the ocean responses to the same AO forcing are much larger under the sea ice condition in the 2010s for both Arctic total FWC (by up to 50%) and regional SSH and velocity (doubled in some places). Sea ice decline intensifies ocean responses to the BH forcing in the Canada Basin with a similar strength. The Arctic Dipole Anomaly (DA) causes opposite changes in FWC between the Eurasian and Amerasian sectors in the cold decade, with the impact through changing sea ice thermodynamics being nonnegligible compared with that through changing ocean surface stress. Sea ice decline makes the ocean response to DA forcing less regular spatially. This study indicates an increasing vulnerability of the Arctic Ocean to winds in a warming world, which implies that extreme marine events may occur more often in the future. Plain Language Summary The freshwater that is retained in the Arctic Ocean not only significantly influences the Arctic Ocean stratification, dynamic sea level, circulation and ecosystem, but also can influence the ocean circulation over a much larger region of the globe when it is released through the Arctic gateways. This study reveals that the ongoing Arctic sea ice decline significantly intensifies the decadal variability of Arctic FWC, sea level and upper ocean circulation. That is, the physical and potentially the biogeochemical environments of the Arctic Ocean are becoming more vulnerable to variations in surface winds when sea ice declines in a warming climate. Extreme events, like higher than normal FWC and ocean current speeds in some Arctic regions, will possibly occur more often in the new Arctic Ocean.

Automated summary

This study reveals that ongoing Arctic sea ice decline significantly intensifies the decadal variability of Arctic liquid freshwater content, sea level, and upper ocean circulation, indicating an increasing vulnerability of the Arctic Ocean to winds in a warming world. Extreme marine events may occur more often in the future as the physical and potentially biogeochemical environments of the Arctic Ocean become more vulnerable to variations in surface winds with sea ice decline.