Extreme Events and the Melting of Greenland: Heat Waves and Hurricanes

The recent two decades have seen increased melting of the Greenland Ice Sheet (GIS) (e.g. Tedesco and Fettweis, 2020, The Cryosphere), in part due to the increasing frequency of Atmospheric Rivers impacting the GIS (Mattingly et al., 2018, JGR). In 2012, the GIS saw two melt episodes with nearly complete coverage over the ice sheet whereas most recently, in 2019, two more less-extensive surface melt episodes occurred. Prior to the current century, events of this kind last occurred in 1889 and prior to that during the medieval climate anomaly (~950 to 1250 CE). Whereas GIS-wide surface melt episodes have attracted the most attention, as in 2012, other impactful melt episodes and surface mass losses have been confined to the coastal and ablation zones where runoff reaches the ocean, such occurred in 2011 (Doyle et al., 2015, Nat. Geo.) Of interest in Doyle et al.'s August 2011 case is that it occurred in concert with Hurricane Irene moving northward in the Atlantic and decaying as an extratropical cyclone at the southern tip of the GIS. In advance of Irene, an AR initiated the episode (Neff, 2018, Nat. Clim. Change) and as we have now discovered, Irene followed the same isobaric pathway from the subtropics. Such combinations of ARs and hurricane sources have, in the past, been identified as resulting in heavy rainfall in the mountains of Norway at 60N (Stohl et al., 2008, JGR). In this latter case, the orientation of the mountains was transverse to the incident flow leading to significant increases in precipitation unlike the cases in Greenland where the flows are more likely aligned along the coast.

In this talk, we will examine the most recent cases in the context of the now-well-studied 2012 melt episode with respect to the extent of melt as well as the large-scale meteorological environment. This examination will consider continental heat anomalies, ARs, and subtropical moisture transport (hurricanes).