Glacier dynamics at Helheim and Kangerdlugssuaq glaciers, southeast Greenland, since the Little Ice Age

摘要

Observations over the past decade show significant ice loss associated withthe speed-up of glaciers in southeast Greenland from 2003, followed by adeceleration from 2006. These short-term, episodic, dynamic perturbationshave a major impact on the mass balance on the decadal scale. To improve theprojection of future sea level rise, a long-term data record that revealsthe mass balance beyond such episodic events is required. Here, we extendthe observational record of marginal thinning of Helheim and Kangerdlugssuaqglaciers from 10 to more than 80 years. We show that, although the frontalportion of Helheim Glacier thinned by more than 100 m between 2003 and 2006,it thickened by more than 50 m during the previous two decades. In contrast,Kangerdlugssuaq Glacier underwent minor thinning of 40–50 m from 1981 to1998 and major thinning of more than 100 m after 2003. Extending the recordback to the end of the Little Ice Age (prior to 1930) shows no thinning ofHelheim Glacier from its maximum extent during the Little Ice Age to 1981,while Kangerdlugssuaq Glacier underwent substantial thinning of 230 to265 m. Comparison of sub-surface water temperature anomalies and variationsin air temperature to records of thickness and velocity change suggest thatboth glaciers are highly sensitive to short-term atmospheric and oceanforcing, and respond very quickly to small fluctuations. On centurytimescales, however, multiple external parameters (e.g. outlet glaciershape) may dominate the mass change. These findings suggest that specialcare must be taken in the projection of future dynamic ice loss.