Eemian Greenland ice sheet simulated with a higher-order model shows strong sensitivity to surface mass balance forcing

Andreas Plach,Sébastien Le Clec'H,Kerim H Nisancioglu,Andreas Born,Petra M Langebroek

doi:10.5194/tc-13-2133-2019

Abstract

Abstract. The Greenland ice sheet contributes increasingly to global sea level rise. Its history during past warm intervals is a valuable reference for future sea level projections. We present ice sheet simulations for the Eemian interglacial period (∼130 000 to 115 000 years ago), a period with warmer-than-present summer climate over Greenland. The evolution of the Eemian Greenland ice sheet is simulated with a 3-D higher-order ice sheet model, forced with a surface mass balance derived from regional climate simulations. Sensitivity experiments with various surface mass balances, basal friction, and ice flow approximations are discussed. The surface mass balance forcing is identified as the controlling factor setting the minimum in Eemian ice volume, emphasizing the importance of a reliable surface mass balance model. Furthermore, the results indicate that the surface mass balance forcing is more important than the representation of ice flow for simulating the large-scale ice sheet evolution. This implies that modeling of the future contribution of the Greenland ice sheet to sea level rise highly depends on an accurate surface mass balance.

Highlights

The simulation of the Greenland ice sheet (GrIS) under past warmer climates is a valuable way to test methods used for sea level rise projections
There is a distinct difference between the model experiments forced with the two surface mass balance (SMB): forcing the ice sheet with Modèle Atmosphérique Régional (MAR)-surface energy balance (SEB) SMB gives a minimum ice volume of 2.73 × 1015 m3 at 124.7 ka, corresponding to a sea level rise of 0.5 m – the basal sensitivity experiments give a range of 0.3 to 0.7 m
This study emphasizes the importance of an accurate surface mass balance (SMB) forcing over a more complex ice flow approximation for the simulation of the Greenland ice sheet during the Eemian

Summary

Introduction

The simulation of the Greenland ice sheet (GrIS) under past warmer climates is a valuable way to test methods used for sea level rise projections. The Eemian summer temperature is estimated to have been 4– 5 ◦C above present over most Arctic land areas (e.g., Capron et al, 2017) and an ice core record from NEEM (the North Greenland Eemian Ice Drilling project in northwest Greenland; NEEM community members, 2013) indicates a local warming of 8.5 ± 2.5 ◦C (Landais et al, 2016) compared to pre-industrial levels. Coral-reef-derived global mean sea level estimates show values of at least 4 m above the present level (Overpeck et al, 2006; Kopp et al, 2013; Dutton et al, 2015) While this could indicate a reduced Antarctic ice sheet, the contribution from the GrIS to the Eemian sea level highstand remains unclear. Previous modeling studies focusing on Greenland (e.g., Letréguilly et al, 1991; Otto-Bliesner et al, 2006; Robinson et al, 2011; Born and Nisancioglu, 2012; Stone et al, 2013; Helsen et al, 2013) used very different setups and forcing, and show highly variable results

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Discussion

Conclusion