27 Feb 2024
 | 27 Feb 2024
Status: this preprint is open for discussion and under review for Climate of the Past (CP).

The comparative role of physical system processes in Hudson Strait ice stream cycling: a comprehensive model-based test of Heinrich event hypotheses

Kevin Hank and Lev Tarasov

Abstract. Despite their recognized significance on global climate and extensive research efforts, the mechanism(s) driving Heinrich Events remain(s) a subject of debate. Here, we use the 3D thermo-mechanically coupled Glacial Systems Model (GSM) to examine Hudson Strait ice stream surge cycling as well as the role of 3 factors previously hypothesized to play a critical role in Heinrich events: ice shelves, glacial isostatic adjustment, and sub-surface ocean temperature forcings. In contrast to all previous modeling studies examining HEs, the GSM uses a transient last glacial cycle climate forcing, global visco-elastic glacial isostatic adjustment model, and sub-glacial hydrology model. The results presented here are based on a high-variance sub-ensemble retrieved from North American history matching for the last glacial cycle.

Over our comparatively wide sampling of the potential parameter space (52 ensemble parameters for climate forcing and process uncertainties), we find two modes of Hudson Strait ice streaming: classic binge-purge versus near continuous ice streaming with occasional shutdowns and subsequent surge onset overshoot. Our model results indicate that large ice shelves covering the Labrador Sea during the last glacial cycle only occur when extreme calving restrictions are applied. The otherwise minor ice shelves provide insignificant buttressing for the Hudson Strait ice stream. While sub-surface ocean temperature forcing leads to minor differences regarding surge characteristics, glacial isostatic adjustment does have a significant impact. Given input uncertainties, the strongest controls on ice stream surge cycling are the poorly constrained deep geothermal heat flux under Hudson Bay and Hudson Strait and the basal drag law. Decreasing the geothermal heat flux within available constraints and/or using a Coulomb sliding law instead of a Weertman-type power law leads to a shift from the near-continuous streaming mode to the binge-purge mode.

Kevin Hank and Lev Tarasov

Status: open (until 23 Apr 2024)

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Kevin Hank and Lev Tarasov

Video supplement

Supplementary material for "The comparative role of physical system processes in Hudson Strait ice stream cycling: a comprehensive model-based test of Heinrich event hypotheses" Kevin Hank

Kevin Hank and Lev Tarasov


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Short summary
The ice-rafted debris signature of Heinrich Events in marine sedimentary cores is usually attributed to massive ice discharge from the Laurentide ice sheet. However, the driving mechanism of this pulsed discharge remains unclear. We compare three previously proposed hypotheses and examine the role of relevant system processes. We find ice stream surge cycling is the most likely mechanism, but its character is sensitive to both the geothermal heat flux and the form of the basal drag law.