The role of basal hydrology in the surging of the Laurentide Ice Sheet

Abstract

Abstract. We use the Glimmer ice sheet model to simulate periodic surges over the Laurentide Ice Sheet during the Last Glacial Maximum. In contrast to previous studies we use the depth of water at the base of the ice sheet as the switch for these surges. We find that the surges are supported within the model and are quite robust across a very wide range of parameter choices, in contrast to many previous studies where surges only occur for rather specific cases. The robustness of the surges is likely due to the use of water as the switch mechanism for sliding The statistics of the binge-purge cycles resemble observed Heinrich Events. The events have a period of between 10–15 thousand years and can produce fluxes of ice from the mouth of Hudson Strait of 0.05 Sv – a maximum flux of 0.06 Sv is possible. The events produce an ice volume of 2.50 × 106 km3 with a range of 4.30 × 106 km3–1.90 × 106 km3 possible. We undertake a suite of sensitivity tests varying the sliding parameter, the water drainage scheme, the sliding versus water depth parametrization, and the resolution all of which support the ice sheet surges. This suggests that internally triggered ice sheet surges were a robust feature of the Laurentide Ice Sheet and are a possible explanation for the observed Heinrich Events.

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

“…The surge phase stops when heat generation from internal deformation decreases and cannot maintain basal temperatures at the pressure melting point, resulting in an abrupt stop of basal sliding. Based on the binge-purge mechanism, a number of studies using ice-sheet models of different complexity have been able to reproduce quasi-periodic surge events for synthetic (Payne, 1995;Calov et al, 2010;Feldmann and Levermann, 2017) and real-world geometries (Marshall and Clarke, 1997;Calov et al, 2002;Roberts et al, 2016;Ziemen et al, 2019). The parameterisations that determine the onset of rapid basal sliding, however, differ between these studies, with some using a temperature switch (Marshall and Clarke, 1997;Calov et al, 2002Calov et al, , 2010 and others using a subglacial water availability switch (Roberts et al, 2016;Feldmann and Levermann, 2017).…”

“…Straneo and Heimbach, 2013;Murray et al, 2015). Until now, there have only been a couple of attempts to systematically investigate the sensitivity of ice-sheet surges to different boundary forcing perturbations (Calov et al, 2010;Roberts et al, 2016).…”

Assimilating the ICE‐6G_C Reconstruction of the Latest Quaternary Ice Age Cycle Into Numerical Simulations of the Laurentide and Fennoscandian Ice Sheets

“…GIA physics describes the way in which the solid surface of the Earth adjusts along with sea level in response to the evolution of ice sheets (e.g., Peltier, ), whose interactions with the atmosphere and ocean involve highly nonlinear feedbacks and instabilities. The grounding line instability (Schoof, ), the Heinrich instability (e.g., Hemming, ; Hulbe et al, ; MacAyeal, ; Marshall & Clarke, ; Roberts et al, ), and the Dansgaard‐Oeschger (D‐O) oscillation (e.g., Peltier & Vettoretti, ; Vettoretti & Peltier, , ) may all have been important contributors to high‐frequency (1–10 kyr) surface climate variability that is today evidenced in Greenland and Antarctic ice cores as distinct inferred variations of atmospheric temperature (e.g., Johnsen et al, ; Petit et al, ). Based upon oxygen isotopic evidence from marine sediment cores (see, e.g., Imbrie & McIntyre, ; Imbrie et al, ), the observational record of past eustatic sea level variation exhibits further, but somewhat more muted, evidence of such instances of rapid climate change.…”