资源环境科技发展态势分析平台

The Beaufort Gyre (BG) is the largest liquid freshwater reservoir of the Arctic Ocean. The liquid freshwater content (FWC) significantly increased in the BG in the 2000s during an anticyclonic wind regime and remained at a high level despite a transition to a more cyclonic state in the early 2010s. It is not well understood to what extent the rapid sea ice decline during this period has modified the trend and variability of the BG liquid FWC in the past decade. Our numerical simulations show that about 50% of the liquid freshwater accumulated in the BG in the 2000s can be explained by the sea ice decline caused by the Arctic atmospheric warming. Among this part of the FWC increase, 60% can be attributed to surface freshening associated with the reduction of the net sea ice thermodynamic growth rate, and 40% to changes in ocean circulation, which makes freshwater more accessible to the BG for storage. Thus, the rapid increase of the BG FWC in the 2000s was due to the concurrence of the anticyclonic wind regime and the high freshwater availability. We also find that if the Arctic sea ice had not declined, the liquid FWC in the BG would have shown a stronger decreasing tendency at the beginning of the 2010s owing to the cyclonic wind regime. From our results we argue that changes in sea ice conditions should be adequately taken into account when it comes to understanding and predicting variations of BG liquid FWC in a changing climate.

Plain Language Summary Arctic Ocean is undergoing unprecedented changes, with significant accumulation of liquid freshwater. If the accumulated freshwater in the Arctic Ocean is released to the North Atlantic, it might significantly influence the large-scale ocean circulation and climate through its impact on deep water formation. The Beaufort Gyre (BG) is the Arctic Ocean's largest liquid freshwater reservoir. Its liquid freshwater content (FWC) increased significantly in the 2000s. At the same time Arctic sea ice has declined rapidly. A crucial question needs to be answered: To what extent the sea ice decline has modified the trend and variability of the BG liquid FWC? Our numerical simulations show that about 50% of the liquid freshwater accumulated in the BG in the 2000s can be explained by sea ice decline. Among this part of the FWC increase, 60% can be attributed to surface freshening associated with the reduction of the net sea ice thermodynamic growth rate, and 40% is due to changes in ocean circulation, which helped advect freshwater to the BG. From our results we argue that changes in sea ice conditions should be adequately taken into account when it comes to understanding and predicting variations of Arctic FWC in a changing climate.