03 Jul 2023
 | 03 Jul 2023
Status: this preprint is currently under review for the journal CP.

Late Pleistocene glacial terminations accelerated by proglacial lakes

Meike Scherrenberg, Constantijn Berends, and Roderik van de Wal

Abstract. During the glacial cycles of the past 800 thousand years, Eurasia and North America were periodically covered by large ice sheets. While the Late Pleistocene glacial cycles typically lasted 80 – 120 thousand years, the termination phases only took 10 thousand years to complete. During these glacial terminations, the North American and Eurasian ice sheets retreated which created large proglacial lakes in front of the ice sheet margin. Proglacial lakes accelerate the deglaciation as they can facilitate ice shelves in the southern margins of the North American and the Eurasian ice sheets. Ice shelves are characterized by basal melting, low surface elevations and negligible friction at the base. Here we quantify the effect of proglacial lakes, and the combined effect with glacial isostatic adjustment (GIA) on Late Pleistocene glacial terminations.

We find that proglacial lakes accelerate the deglaciation of the ice sheets mainly because of the absence of basal friction underneath ice shelves. If the friction underneath grounded ice is applied to floating ice, we find that full deglaciation is postponed by a few millennia, the Barents-Kara Sea region does not fully deglaciate, and there are no extensive ice shelves. Additionally, the large uncertainty in melt rates underneath lacustrine ice shelves translates to an uncertainty in the timing of the termination of only a few centuries at most.

Proglacial lakes are created by the depression in the landscape that linger after the ice sheet has retreated. The depth, size and timing of proglacial lakes depend on the bedrock rebound. We find that if the bedrock rebounds within a few centuries, instead of a few millennia, the mass loss rate of the ice sheet is substantially reduced. This is because fast bedrock rebound prevents the formation of extensive proglacial lakes. Additionally, a decrease in thickness is partly compensated by the faster bedrock rebound, resulting in a higher surface elevation with lower temperatures and higher surface mass balance delaying deglaciation. We find that a very long bedrock relaxation time does not affect terminations substantially, but will lead to a later inception of the next glacial period. This is because initial inception regions, such as North-Western Canada, remain below sea level throughout the preceding interglacial period.

Meike Scherrenberg et al.

Status: open (until 21 Oct 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2023-42', Niall Gandy, 08 Aug 2023 reply

Meike Scherrenberg et al.

Data sets

IMAU-ICE output M. D. W. Scherrenberg, C. J. Berends, R. S. W. van de Wal

Model code and software

IMAU-ICE model code and Matlab scripts for figures M. D. W. Scherrenberg, C. J. Berends, R. S. W. van de Wal

Meike Scherrenberg et al.


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Short summary
During Late Pleistocene glacial cycles, the Eurasian and North American ice sheets grew and melted resulting in over 100 meters of sea level change. Studying the melt of past ice sheets can improve our understanding of how ice sheets respond in the future. In this study we find that melt is increased due to proglacial lakes that form at the margins of the ice sheets, mostly due to the reduced basal friction of floating ice. Furthermore, bedrock uplift rates can strongly influence melt.