30 May 2022
30 May 2022
Status: this preprint is open for discussion and under review for Climate of the Past (CP).

Sensitivity of Heinrich-type ice-sheet surge characteristics to boundary forcing perturbations

Clemens Schannwell1, Uwe Mikolajewicz1, Florian Ziemen2, and Marie-Luise Kapsch1 Clemens Schannwell et al.
  • 1Max Planck Institute for Meteorology, Bundesstraße 53, 20146 Hamburg, Germany
  • 2Deutsches Klimarechenzentrum, Bundesstr. 45a, 20146 Hamburg, Germany

Abstract. Heinrich-type ice-sheet surges are one of the dominant signals of glacial climate variability. They are characterised as abrupt, quasi-periodic episodes of ice-sheet instabilities during which large amounts of ice are discharged from ice sheets into the ocean. The occurence of ice-sheet surges strongly influences the global climate evolution by altering the ocean circulation through the addition of freshwater and the atmospheric circulation through changes in ice-sheet height. The mechanisms controlling the timing and occurence of Heinrich-type ice-sheet surges remain poorly constrained to this day. Here, we use a coupled ice sheet-solid earth model to identify and quantify the importance of boundary forcing for the surge cycle length of Heinrich-type ice-sheet surges for two prominent ice streams of the Laurentide ice sheet – the land-terminating Mackenzie ice stream and the marine-terminating Hudson ice stream. We show that surface mass balance perturbations have the largest effect on the surge cycle length. Pertubations to the ice surface temperature and geothermal heatflux also influence the surge cycle length, but to a lesser degree. Ocean and sea-level forcing as well as different frequencies of the same forcing have a negligible effect on the surge cycle length. The simulations also highlight that only a certain parameter space exists under which ice-sheet oscillations can be maintained. Transitioning from an oscillatory state to a persistent ice streaming state, can result in an ice volume loss of up to 26 % for the respective ice stream drainage basin under otherwise constant climate conditions. We show that Mackenzie ice stream is susceptible to undergoing such a transition in response to all tested positive climate perturbations. This underlines the potential of the Mackenzie region to have contributed to prominent abrupt climate change events of the last deglaciation.

Clemens Schannwell et al.

Status: open (until 06 Aug 2022)

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Clemens Schannwell et al.

Clemens Schannwell et al.


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Short summary
Heinrich-type ice sheet surges are recurring events over the course of the last glacial cycle during which large amounts of icebergs are discharged from the Laurentide ice sheet into the ocean. These events alter the evolution of the global climate. Here, we use model simulations of the Laurentide ice sheet to identify and quantify the importance of various climate and ice sheet parameters on the simulated surge cycle.