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Rise of Great Lakes Surface Water, Sinking of the Upper Midwest of the United States, and Viscous Collapse of the Forebulge of the Former Laurentide Ice Sheet
Author(s) -
Argus Donald F.,
Ratliff Benjamin,
DeMets Charles,
Borsa Adrian A.,
Wiese David N.,
Blewitt Geoffrey,
Crowley John W.,
Martens Hilary R.,
Kreemer Corné,
Landerer Felix W.
Publication year - 2020
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1029/2020jb019739
Subject(s) - geology , greenland ice sheet , ice sheet , surface water , hydrology (agriculture) , groundwater , oceanography , physical geography , environmental science , geography , geotechnical engineering , environmental engineering
Great Lakes water levels rose 0.7–1.5 m from 2013 to 2019, increasing surface water volume by 285 km 3 . Solid Earth's elastic response to the increased mass load is nearly known: The Great Lakes floor fell 8–23 mm, and the adjacent land fell 3–14 mm. Correcting GPS measurements for this predicted elastic loading (1) straightens position‐time series, making the evolution of position more nearly a constant velocity and (2) reduces estimates of subsidence rate in Wisconsin, Michigan, and southern Ontario by 0.5–2 mm/yr, improving constraints on postglacial rebound. GPS records Wisconsin and Michigan to have subsided at 1–4 mm/yr. We find this sinking to be produced primarily by viscous collapse of the former Laurentide ice sheet forebulge and secondarily by elastic Great Lakes loading. We infer water on land in the Great Lakes watershed to be total water change observed by GRACE minus Great Lakes surface water smeared by a Gaussian distribution. Water stored on land each year reaches a maximum in March, 6 months before Great Lakes water levels peak in September. The seasonal oscillation of water on land in the Great Lakes basin, 100 km 3 (0.20 m water thickness), is twice that in a hydrology model. In the seasons, groundwater in the Great Lakes watershed increases by 60 km 3 (0.12 m) each autumn and winter and decreases by roughly an equivalent amount each spring and summer. In the long term, groundwater volume remained constant from 2004 to 2012 but increased by 50 km 3 (0.10 m) from 2013 to 2019.