Simulation of the Greenland Ice Sheet over two glacial–interglacial cycles: investigating a sub-ice- shelf melt parameterization and relative sea level forcing in an ice-sheet–ice-shelf model

Abstract

Abstract. Observational evidence, including offshore moraines and sediment cores, confirm that at the Last Glacial Maximum (LGM) the Greenland ice sheet (GrIS) expanded to a significantly larger spatial extent than seen at present, grounding into Baffin Bay and out onto the continental shelf break. Given this larger spatial extent and its close proximity to the neighbouring Laurentide Ice Sheet (LIS) and Innuitian Ice Sheet (IIS), it is likely these ice sheets will have had a strong non-local influence on the spatial and temporal behaviour of the GrIS. Most previous paleo ice-sheet modelling simulations recreated an ice sheet that either did not extend out onto the continental shelf or utilized a simplified marine ice parameterization which did not fully include the effect of ice shelves or neglected the sensitivity of the GrIS to this non-local bedrock signal from the surrounding ice sheets.In this paper, we investigated the evolution of the GrIS over the two most recent glacial-interglacial cycles (240 ka BP to the present day) using the ice-sheet-ice-shelf model IMAU-ICE. We investigated the solid earth influence of the LIS and IIS via an offline relative sea level (RSL) forcing generated by a glacial isostatic adjustment (GIA) model. The RSL forcing governed the spatial and temporal pattern of sub-ice-shelf melting via changes in the water depth below the ice shelves.In the ensemble of simulations, at the glacial maximums, the GrIS coalesced with the IIS to the north and expanded to the continental shelf break to the southwest but remained too restricted to the northeast. In terms of the global mean sea level contribution, at the Last Interglacial (LIG) and LGM the ice sheet added 1.46 and −2.59 m, respectively. This LGM contribution by the GrIS is considerably higher (∼ 1.26 m) than most previous studies whereas the contribution to the LIG highstand is lower (∼ 0.7 m). The spatial and temporal behaviour of the northern margin was highly variable in all simulations, controlled by the sub-ice-shelf melting which was dictated by the RSL forcing and the glacial history of the IIS and LIS. In contrast, the southwestern part of the ice sheet was insensitive to these forcings, with a uniform response in all simulations controlled by the surface air temperature, derived from ice cores.

Submarine melt as a potential trigger of the North East Greenland Ice Stream margin retreat during Marine Isotope Stage 3

“…S4 in the Supplement), that is underestimated as compared to other recent modelling work (Lecavalier et al, 2014;Tabone et al, 2018). Nevertheless, our estimation is not far from others (Huybrechts, 2002;Simpson et al, 2009) and well within the range proposed by Buizert et al (2018). Note that although the LGM extent simulated by Lecavalier et al (2014) is smaller than ours in the north-east, their ice volume contribution during the glacial maximum is about 1 m sea-level equivalent (SLE) higher.…”

“…Even in the unperturbed experiment, which allows the largest icesheet expansion due to the absence of melting at the marine margins, the grounding line does not reach the continental shelf break. Nevertheless, our simulated extent is still one of the best reconstructions of north-east Greenland during the LGM obtained with an ice-sheet model (Bradley et al, 2018;Lecavalier et al, 2014;Simpson et al, 2009;Tabone et al, 2018). This discrepancy in the LGM extents is reflected in the transient GrIS sea-level contribution from the LGM to the present (Fig.…”

Application of HadCM3@Bristolv1.0 simulations of paleoclimate as forcing for an ice-sheet model, ANICE2.1: set-up and benchmark experiments

“…Several studies of past glacial cycles using ice-sheet models (Bintanja et al, 2002;) apply a present-day climate with a uniform temperature offset based on a "glacial index", usually from ice-core isotope records, adapting precipitation based on a Clausius-Clapeyron-type relationship. Others have used a similar glacial index to create a linear combination of output of different GCM timeslice simulations (Marshall et al, 2000(Marshall et al, , 2002Charbit et al, 2002Charbit et al, , 2007Tarasov and Peltier, 2004;Zweck and Huybrechts, 2005;Niu et al, 2017). Both types of studies share the shortcoming of having no clear physical cause for the prescribed climatological variations and no explicit feedback from the cryosphere back onto the prescribed climate.…”

The impact of model resolution on the simulated Holocene retreat of the southwestern Greenland ice sheet using the Ice Sheet System Model (ISSM)

“…Southwestern Greenland is an area that experienced a large reduction in ice sheet extent. The ice margin retreated on the order of 150 km inland from the present-day coastline in response to warming during the early and middle Holocene (Briner et al, 2016). This landscape is punctuated by widely traceable moraine sequences (Weidick, 1968;Ten Brink and Weidick, 1974) that extend nearly 600 km throughout western Greenland and provide a constraint on the past retreat pattern of the GrIS in this region; the chronology of these moraines continues to be refined (Weidick et al, 2004(Weidick et al, , 2012Young et al, 2013;Larsen et al, 2015;Lesnek and Briner, 2018).…”