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On the limited ice intrusion in Alaska at the LGM
Author(s) -
Löfverström Marcus,
Liakka Johan
Publication year - 2016
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2016gl071012
Subject(s) - ice sheet , climatology , geology , last glacial maximum , precipitation , shortwave radiation , shortwave , atmospheric sciences , glacial period , environmental science , oceanography , geomorphology , radiative transfer , geography , meteorology , radiation , physics , quantum mechanics
The Last Glacial Maximum (LGM) Laurentide Ice Sheet covered most of the North American continent poleward of 40°N, with the exception of Alaska that remained relatively warm, dry, and largely ice free. Experiments with a global atmospheric circulation model are in broad agreement with proxies: the Alaskan summer temperatures are comparable to the preindustrial, and the annual precipitation is reduced by 30–50%. The warm conditions are attributed to a lowering of the local planetary albedo—due to a decreased cloudiness in response to the cold LGM sea surface temperatures (SSTs) and a stationary anticyclone forced by the ice sheet—that allows more shortwave radiation to reach the surface. Stationary waves are shown to counteract the shortwave cloud feedback by converging less heat over the target region. The LGM SST field also yields an equatorward shifted Pacific stormtrack, which results in drier conditions in Alaska and abundant precipitation at the southern margin of the Laurentide Ice Sheet.