Preprints
https://doi.org/10.5194/tc-2022-215
https://doi.org/10.5194/tc-2022-215
 
09 Nov 2022
09 Nov 2022
Status: this preprint is currently under review for the journal TC.

Simulating the Laurentide ice sheet of the Last Glacial Maximum

Daniel Moreno1,2, Jorge Alvarez-Solas1,2, Javier Blasco1,2, Marisa Montoya1,2, and Alexander Robinson1,2,3 Daniel Moreno et al.
  • 1Departamento de Física de la Tierra y Astrofísica, Universidad Complutense de Madrid, Facultad de Ciencias Físicas, 28040 Madrid, Spain
  • 2Instituto de Geociencias, Consejo Superior de Investigaciones Cientifícas-Universidad Complutense de Madrid, 28040 Madrid, Spain
  • 3Potsdam Institute for Climate Impact Research, 14473 Potsdam, Germany

Abstract. In the last decades, great effort has been made to reconstruct the Laurentide Ice Sheet (LIS) during the Last Glacial Maximum (LGM, ca. 21,000 years before present, 21 kyr ago). Uncertainties underlying its modelling have led to large differences in fundamental features such as its maximum elevation, extension and total volume. However, the uncertainty in ice dynamics and thus in ice extension, volume and ice-stream stability remains large. We herein use a higher-order three-dimensional ice-sheet model to simulate the LIS under LGM boundary conditions for a number of basal friction formulations of varying complexity. Their consequences on the Laurentide ice streams, configuration, extension and volume are explicitly quantified. Total volume and ice extent generally reach a constant equilibrium value that falls close to prior LIS reconstructions. Simulations exhibit high sensitivity to the dependency of the basal shear stress on the sliding velocity. In particular, a regularized-Coulomb formulation appears to be the best choice in terms of ice volume and ice-stream realism. Notable differences are found when the stress balance is thermomechanically coupled: the LIS volume is lower than for a purely mechanical friction scenario and the base remains colder. Thermomechanical coupling is fundamental for producing rapid ice streaming, yet it leads to a similar distribution of ice overall.

Daniel Moreno et al.

Status: open (until 07 Jan 2023)

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Daniel Moreno et al.

Daniel Moreno et al.

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Short summary
We have reconstructed the Laurentide Ice Sheet, placed in North America during the Last Glacial Maximum (21,000 years ago). The absence of direct measurements raises a number of uncertainties. Here we study the impact of different physical laws that describe the friction as the ice slides over its base. We found that the Laurentide Ice Sheet is closest to prior reconstructions when the basal friction takes into account whether the base is frozen or thawed during its motion.