The past decade has seen an exceptional number of unprecedented summer extreme weather events1, 2, 3, 4 in northern mid-latitudes, along with record declines in both summer Arctic sea ice5, 6 and snow cover on high-latitude land7. The underlying mechanisms that link the shrinking cryosphere with summer extreme weather, however, remain unclear8, 9, 10, 11, 12. Here, we combine satellite observations of early summer snow cover and summer sea-ice extent13 with atmospheric reanalysis data14 to demonstrate associations between summer weather patterns in mid-latitudes and losses of snow and sea ice. Results suggest that the atmospheric circulation responds differently to changes in the ice and snow extents, with a stronger response to sea-ice loss, even though its reduction is half as large as that for the snow cover. Atmospheric changes associated with the combined snow/ice reductions reveal widespread upper-level height increases, weaker upper-level zonal winds at high latitudes, a more amplified upper-level pattern, and a general northward shift in the jet stream. More frequent extreme summer heat events over mid-latitude continents are linked with reduced sea ice and snow through these circulation changes.
At a glance
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