A two-part analysis of the Greenland Ice Sheet using glacial isostatic adjustment and bare ice albedo: from past and present to future

Abstract

Global sea level rise is a major present-day and future concern as it directly affects many people living in coastal communities. The Greenland Ice Sheet (GrIS) is currently the largest contributing ice sheet to global sea level rise, though it remains unclear, however, exactly how much sea level is going to rise and what role meltwater from the GrIS is going to play. To understand the behaviour of the GrIS in the future, we need to understand its behaviour both in the past and present. In this thesis I therefore focus on aspects of both the historic as well as the present-day contribution to sea level rise from the GrIS. The first chapter contains a study of the sensitivity of the GrIS to a historic warmer-than-present climate during the Holocene Thermal Maximum (HTM; ∼11-5 ka). During this period, especially Southwest Greenland was exposed to a warmer climate. In this study I focus on the extent of the ice margin in Southwest Greenland to increased temperatures during the HTM and what effect a changing ice margin has on the long-term viscoelastic response of the solid Earth underlying the southwestern region of the GrIS. By doing this, I infer what ongoing adjustments of the changing ice mass load since the Last Glacial Maximum (26.5-20 ka) are present in current sea level and geodetic signals in Southwest Greenland and how this affects our understanding of present-day ice melt from the GrIS. The second chapter contains a study of the present-day behaviour of the GrIS. In particular, the variability of the extent and albedo of the bare ice zone. Bare ice is responsible for the majority of meltwater production and runoff from the GrIS through its low albedo and absorption of solar radiation. Proper representation of the bare ice zone in climate models is thus imperative for accurately modeling future melt from the GrIS. In this study I focus on the representation of the bare ice extent and albedo variability on the GrIS in the Modèle Atmosphérique Régional (MAR), a regional climate model. I compare MAR model output with satellite imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) to isolate differences between modeling and remote sensing data and highlight regions for climate model improvement. Focusing on both the historic and present-day behaviour of the GrIS through a multidisciplinary approach allows me to more broadly investigate the processes governing historic, present-day and future ice mass loss and associated sea level rise.