New projections of winter Euro-Atlantic atmospheric blocking activity under strong warming scenario and consequences for Arctic land and sea ice

Atmospheric blockings have widespread, long-lasting, and severe consequences in a variety of regions, causing climate extremes such as drought, heavy rainfall, cold spells, and heatwaves. Depending on where the blocking occurs, climate anomalies caused by high-latitude Euro-Atlantic winter blockings, in particular, have a significant impact on Arctic sea ice export in the North Atlantic, and thus on the freshwater budget in deepwater formation regions, and also impact Greenland ice cap and Arctic sea ice recovery during the cold polar season. Understanding the evolution of future winter Euro-Atlantic blockings in the context of climate change is thus critical for accurately predicting future changes in cryosphere systems and ocean circulation. The future evolution of these blockings, however, remains highly uncertain because coupled climate models generally fail to reproduce their frequencies of occurrence and spatial locations in historical runs. Meanwhile, recent research has shown that historical atmospheric blockings are much better simulated in climate models with eddy-permitting ocean resolutions due to more accurately represented mean climate states and air-sea interactions. Here, we show that eddy-permitting climate models provide blocking projections with much lower uncertainties in terms of frequency and spatial extent by using an ensemble of more than a hundred of CMIP6 climate model simulations, both ran with and without eddying ocean models. Finally, we show from the set of model simulations with eddying ocean models that the frequency of blocking types leading to dryer and warmer winter conditions in North Atlantic-Arctic regions for the next three decades is likely to increase under strong warming scenarios. Such an evolution in blocking activity would trigger large sea ice export events in the North Atlantic and a low rate of recovery of Artic sea ice and the Greenland ice cap during winter, leading to quicker ice loss in general than for climate models with standard ocean grids resolutions.