资源环境科技发展态势分析平台

The Pacific inflow to the Arctic traditionally brings heat in summer, melting sea ice; dense waters in winter, refreshing the Arctic’s cold halocline; and nutrients year‐round, supporting Arctic ecosystems. Bering Strait moorings from 1990‐2019 find increasing (0.010±0.006Sv/yr) northward flow, reducing Chukchi residence times by ∼1.5 months over this period (record maximum/minimum ∼7.5 and ∼4.5 months). Annual mean temperatures warm significantly (0.05±0.02°C/yr), with faster change (∼0.1°C/yr) in warming (June/July) and cooling (October/November) months, which are now 2‐4°C above climatology. Warm (≥0°C) water duration increased from 5.5 months (1990s) to over 7 months (2017), mostly due to earlier warming (1.3±0.7days/yr). Dramatic winter‐only (January‐March) freshening (0.03psu/yr), makes winter waters fresher than summer waters. The resultant winter density change, too large to be compensated by Chukchi sea‐ice processes, shoals the Pacific Winter Water (PWW) equilibrium depth in the Arctic from 100‐150m to 50‐100m, implying PWW no longer ventilates the Arctic’s cold halocline at 33.1psu.