Summer atmospheric circulation over Greenland in response to Arctic amplification and diminished spring snow cover

Abstract

The exceptional atmospheric conditions that have accelerated Greenland Ice Sheet mass loss in recent decades have been repeatedly recognized as a possible dynamical response to Arctic amplification. Here, we present evidence of two potentially synergistic mechanisms linking high-latitude warming to the observed increase in Greenland blocking. Consistent with a prominent hypothesis associating Arctic amplification and persistent weather extremes, we show that the summer atmospheric circulation over the North Atlantic has become wavier and link this wavier flow to more prevalent Greenland blocking. While a concomitant decline in terrestrial snow cover has likely contributed to this mechanism by further amplifying warming at high latitudes, we also show that there is a direct stationary Rossby wave response to low spring North American snow cover that enforces an anomalous anticyclone over Greenland, thus helping to anchor the ridge over Greenland in this wavier atmospheric state.

Attributing Greenland summer temperature extremes to feedback processes and circulation anomalies

“…A second mode, which is anti-correlated with the North Atlantic oscillation, is the Greenland blocking index. The Greenland blocking index, which indicated the strength and frequency of high-pressure blocking conditions over Greenland, was positively correlated with Greenland temperature 10,33,35,[37][38][39][40][41] . Both modes have exerted a substantial impact on the strength and position of the jet stream by increasing the westerly component, reducing the advection of warm and moist air towards Greenland in a positive (negative) phase of the North Atlantic oscillation (Greenland blocking index) 19,32,33 .…”

“…Only during summer, the mean temperature exceeded the freezing point and resulted in snow, ice sheet and glacier melting of varying intensity [1][2][3][4] . Previous studies related enhanced snow and ice sheet melting over Greenland to anomalous warm air advection associated with high-pressure blocking conditions and intensified anticyclonic circulation [4][5][6][7][8][9][10] . For instance, the most recent melt events in 2012 were linked to above-normal temperatures near the surface and in the troposphere, resulting in intense melting, while in 2019, a below-normal snowfall resulted in a negative surface mass balance 9 .…”

“…The ice sheet has undergone a significant negative trend in terms of mass balance 14,15 . Further, there is a significant warming that exceeded the corresponding global average affecting the Arctic and includes Greenland, commonly referred to as Arctic Amplification 10,[15][16][17][18][19][20][21][22][23][24][25] . This warming trend was attributed to local feedback processes [26][27][28][29][30] , especially lapse-rate feedback, the heat release from the Arctic Oceans 16,18,26,31 , and energy transport from lower latitudes 17,27 .…”

“…Other indices of climate variability that exerted teleconnections to Greenland climate conditions include the Scandinavian pattern 43 , the Arctic oscillation 45 , the East Atlantic/West Russia pattern 42 , the East Pacific/North Pacific pattern 42 , the Pacific North America pattern 46 , the Quasi-biennial oscillation 47 , the El Niño-Southern Oscillation 48 , and the Atlantic multi-decadal oscillation 49 . Associated with a positive Greenland blocking index was a high frequency of blocking over Greenland 10,37,40,50 . An anomalous anti-cyclonic circulation and wave breaking at the jet stream and subsidence are characteristics of blocking events 10,41,[51][52][53] .…”

“…Associated with a positive Greenland blocking index was a high frequency of blocking over Greenland 10,37,40,50 . An anomalous anti-cyclonic circulation and wave breaking at the jet stream and subsidence are characteristics of blocking events 10,41,[51][52][53] . Blocking is an important factor affecting regional weather and climate extremes, such as anomalies in the hydroclimate contributing to the development of droughts or extreme rainfalls 50,51 .…”