"Extreme summer weather in northern mid-latitudes linked to a vanishing cryosphere," by Qiuhong Tang, Xuejun Zhang & Jennifer A. Francis, Nature Climate Change

Nature Climate Change, (2013); doi:10.1038/nclimate2065

Extreme summer weather in northern mid-latitudes linked to a vanishing cryosphere

• Qiuhong Tang,
• Xuejun Zhang and
•  Jennifer A. Francis

Abstract

The past decade has seen an exceptional number of unprecedented summer extreme weather events^{1, 2, 3, 4} in northern mid-latitudes, along with record declines in both summer Arctic sea ice^5,6 and snow cover on high-latitude land⁷. The underlying mechanisms that link the shrinking cryosphere with summer extreme weather, however, remain unclear^{8, 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.

http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2065.html