Variability and trends in anticyclonic circulation over the Greenland ice sheet, 1948–2013

Melting and mass loss on the Greenland ice sheet have accelerated in recent years. Possible causes include broader Arctic warming, reduced snow/ice cover, lowered ice sheet albedo, and changes in atmospheric circulation. Anticyclonic ridging over Greenland leads to southerly advection of warm air and clear‐sky conditions, promoting high melt rates. To examine the relative importance of ridging, we examine direct measures of summer 500 hPa anticyclonic circulation strength and frequency in Greenland from 1948 to 2013, isolating the atmospheric circulation signal from 500 hPa geopotential height variations. Anticyclonic circulation anomalies account for 38–49% of the interannual variability and trend in summer air temperature and melt indices. Vorticity‐detrended geopotential height anomalies explain an additional 13–27% of the variance. We identify an abrupt, persistent shift to strong anticyclonic circulation in central Greenland beginning in 2001, which has contributed to recent increases in Greenland ice sheet melt.