Atmospheric destabilization leads to Arctic Ocean winter surface wind intensification

The surface-amplified winter warming over the Arctic Ocean is accompanied by a pronounced intensification of near-surface winds, simulated by climate models and emerging in reanalysis data. Here, the influences of sea-ice decline, wind changes aloft, and atmospheric stability are revisited based on CMIP6 historical and high-emission scenario and ERA5 reanalysis data. Spatial trend patterns suggest that near-surface wind intensification over the inner Arctic Ocean in winter is largely driven by an increasing downward momentum transfer due to a weakening atmospheric stratification. In contrast, a near-surface wind intensification in summer appears to be largely driven by accelerating winds aloft, amplified in a high-emission future by decreasing surface roughness due to sea-ice decline. In both seasons, differences in near-surface wind-speed trends are closely linked to atmospheric stability trends. Models suggest that by 2100 the lower troposphere may become as unstable in winter as in summer, implying a fundamental regime shift of the Arctic winter boundary layer.