|Title||A unique glacial lake-effect environment in the Great Lakes Basin|
|Author||Griggs, C B; Lewis, C F M|
|Source||GSA 2020 Connects Online; Geological Society of America, Abstracts With Programs vol. 52, no. 6, 250-7, 2020 p. 1, https://doi.org/10.1130/abs/2020AM-359278|
|Alt Series||Natural Resources Canada, Contribution Series 20200501|
|Publisher||Geological Society of America|
|Meeting||Geological Society of America Annual Meeting 2020; October 26-30, 2020|
|File format||html; pdf|
|NTS||30; 31C; 31D; 31E; 31F; 31L; 40; 41; 42B; 42C; 42D; 42E; 42F; 42L; 52A; 52B; 52G; 52H; 52I; 52J|
|Area||Great Lakes; New York State; Canada; United States of America|
|Lat/Long WENS|| -94.0000 -76.0000 51.0000 41.0000|
|Subjects||environmental geology; Nature and Environment; glacial lakes; paleoenvironment; glacial history; deglaciation; ice retreat; paleoclimates; paleowinds; paleodrainage; ecosystems; climatology; Great Lakes
Basin; Glacial Lake Iroquois; Glacial Lake Algonquin; Phanerozoic; Cenozoic; Quaternary|
|Released||2020 10 01|
|Abstract||During the Late Glacial (LG) ice recession, 14.2-11.5ka cal BP, changing glacial lake outlets and differential isostatic rebound changed water sources, meltwater distribution, lake configuration and
landscape in the Great Lakes basin. Changes in subfossil logs and other proxy data found downwind of the lakes suggest that the coupling of prevailing winds with the lakes created a unique glacial lake-effect environment, thus climate, within and
downwind of the lakes.|
Today, the Great Lakes affect air temperatures for ~50km and atmospheric moisture up to ~350km downwind of the lakes. During the LG and at least within that area, changes in prevailing winds altered the characteristics and
spatial extent of the lake-effect climate. Over time, a site was successively exposed to easterly winds driven by the glacial anticyclone, turbulence at the wind interface, prevailing westerlies, and drier northwesterlies as the ice sheet receded.
The greater seasonality of the LG interval was amplified by heat and moisture exchange between the winds and frozen vs. open glacial lakes.
A reconstruction of LG climate for the Great Lakes region differs from the accepted progression of the warm
Bølling-Allerød to cold Younger Dryas climate. Rather, climate changes correlate with those in the lakes and surface winds as the ice receded. Ca 14.2-13.1ka cal BP, sustained cold with increasing moisture coincided with the expansion of glacial Lake
Iroquois and drainage of meltwater into New York State. A warming summer trend with decreasing moisture correlated with the demise of Lake Iroquois and end of meltwater flow in New York ca 13.1-12.9ka. The better summers continued and moisture
increased with the expansion of glacial Lake Algonquin ca 12.9-12.5ka. A similar climate with higher variations and decreasing moisture coincided with extensive changes when drainage from Lake Algonquin was re-routed to the north ca 12.5ka-11.9ka.
Drier conditions subsequently prevailed, 11.9-11.5ka. Changes in surface winds across the lakes coincided with changes in lake and landscape configuration and the position of the ice sheet.
A glacial lake-effect environment offers new insight into
modifications of the ecosystems and landscape features downwind of the Great Lakes basin. This study suggests that the Great Lakes may influence climate change in the future.
|Summary||(Plain Language Summary, not published)|
Story about a university field experience(pre GSC) in the 1970's in the Canadian Arctic.Ring width variations in sub-fossil logs from New York State, and
other indicators, during retreat of the Laurentide Ice Sheet reveal changes in climate that correlate best with changes in ice and glacial lakes in the Great Lakes area. This study indicates that the coupling of the de-glacial lake-ice system with
the prevailing winds created a lake-effect climate significantly different than climate outside of the lakes' influence. The affected areas were greater than those affected by the modern lakes' effects. Different glacial lake effects included changes
from sustained cold to warmer summers with increasing, then decreasing moisture as prevailing winds and lake characteristics changed. Generally, a site was successively exposed to easterly winds driven by air circulating around a high pressure cell
over the ice sheet, air turbulence at the easterly-westerly wind interface, prevailing westerlies, and drier northwesterlies as the ice sheet receded. The glacial lake-effect environment offers new insight into modifications of ecosystems and
landscape features downwind of the Great Lakes basin, and the capability of lakes to influence climate change.