An Analysis of Complex Polar-Midlatitude-Tropical Interactions that Culminated in the Largest Greenland Surface Ice-Melt Event of 2019

The largest Greenland surface ice-melt event of 2019 occurred during late July and early August when an astonishing 60% surface areal ice melt was observed according to the National Snow and Ice Data Center. This remarkable surface ice-melt event occurred in conjunction with: (1) the poleward displacement of an Alaskan anticyclone toward the North Pole, (2) the formation of a high-amplitude negatively tilted progressive upper-level trough over the eastern Atlantic, (3) the establishment of a deep southerly flow of very warm air of Saharan origin across western Europe, and (4) the development of a warm upper-level blocking Scandinavian anticyclone that shunted modified Saharan westward toward Greenland.

We use a combination of surface, upper-air and trajectory analyses derived from CFSR gridded reanalysis datasets to diagnose the structure and evolution of the record-breaking Greenland surface ice-melt event of late July and early August 2019. We will show that: (1) the merger of upper-level anticyclones initially situated over Alaska and Scandinavia during late July set the stage for deep easterly flow across Greenland, (2) a progressive negatively tilted North Atlantic upper-level trough facilitated upper-level ridge development from northwestern Africa poleward across western Europe during late July, (3) all-time maximum temperatures over parts of western Europe during late July were a manifestation of the poleward transport of hot Saharan air with standardized anomalies > 4 sigma at 850-hPa toward Scandinavia, and (4) a warm blocking anticyclone that formed over Scandinavia in conjunction with the poleward advection of Saharan air built westward and enabled modified Saharan air to reach Greenland during the period of rapid surface ice melt.