Centennial response of Greenland\u2019s three largest outlet glaciers

Shfaqat Abbas Khan ,Anja Løkkegaard,Kurt H Kjær,Anders A Bjørk,Zhejing Bao ,Trine Dahl‐Jensen ,Michael Bevis,Mathieu Morlighem,Ingo Sasgen,William Colgan,Beáta Csathó ,Lingli Liu ,Nicolaj K Larsen,Niels J Korsgaard,David M Holland,Jason E Box ,Kasper Hjorth Hansen ,Veit Helm,V Barletta ,Anne Søndergaard ,Andy Aschwanden,J Mouginot ,Jonathan Bamber ,Toni Schenk

doi:10.1038/s41467-020-19580-5

Abstract

The Greenland Ice Sheet is the largest land ice contributor to sea level rise. This will continue in the future but at an uncertain rate and observational estimates are limited to the last few decades. Understanding the long-term glacier response to external forcing is key to improving projections. Here we use historical photographs to calculate ice loss from 1880–2012 for Jakobshavn, Helheim, and Kangerlussuaq glacier. We estimate ice loss corresponding to a sea level rise of 8.1 ± 1.1 millimetres from these three glaciers. Projections of mass loss for these glaciers, using the worst-case scenario, Representative Concentration Pathways 8.5, suggest a sea level contribution of 9.1–14.9 mm by 2100. RCP8.5 implies an additional global temperature increase of 3.7 °C by 2100, approximately four times larger than that which has taken place since 1880. We infer that projections forced by RCP8.5 underestimate glacier mass loss which could exceed this worst-case scenario.

Highlights

The Greenland Ice Sheet is the largest land ice contributor to sea level rise
We provide a century-long time series of ice mass change separated into ice dynamics and surface mass balance (SMB) components
We improve the approach described in Kjeldsen et al.[7] to estimate mass loss by including Little Ice Age maximum extent trimlines located in the area between the early 1900s and the 2002 ice margin

Summary

Introduction

The Greenland Ice Sheet is the largest land ice contributor to sea level rise. This will continue in the future but at an uncertain rate and observational estimates are limited to the last few decades. Global mean sea level (GMSL) rose by ~17 centimetres during the 20th century in response to the loss of land-based ice mass, thermal expansion of the oceans, and changes in terrestrial water storage[1,2,3,4,5,6,7,8,9,10,11,12]. This number could increase to 0.7–2 meters by 2100, mainly owing to accelerating ice loss[1]. Helheim Glacier does not have a bed that deepens inland[18,21], allowing us to assess the importance of retrograde bed slopes by comparing Helheim Glacier with

Methods

Results

Conclusion