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. Intensified surface winds over the Arctic are driven by increasing downward momentum transfer in winter and by decreasing surface roughness due to sea-ice decline in summer, suggest analyses of climate model simulations and reanalysis data.