Ice-ocean-atmosphere interactions in the Arctic Seas

Abstract

Arctic ice masses have rapidly lost mass during the past two decades, coincident with marked climatic and oceanic change. Accelerated ice discharge through marine-terminating outlet glaciers has been a primary contributor to deficits. However, substantial uncertainty exists over the factors controlling Arctic outlet glacier dynamics and their spatial variation. This thesis aims to quantify outlet glacier retreat rates across the Atlantic sector of the Arctic and to assess observed changes in relation to climatic, oceanic and glacier-specific controls. Results from a study region in north-west Greenland recorded dramatic retreat on Alison Glacier, coincident with marked atmospheric warming and sea ice decline. However, retreat rates varied substantially within the region, suggesting that fjord width variability and basal topography were important controls on glacier response to external forcing. The influence of fjord width variability was further explored on Novaya Zemlya, Russian High Arctic, where a statistically significant relationship between total retreat and along-fjord width variation was found and the first empirical categories of this relationship were defined. Here, retreat rates were an order of magnitude greater on marine-terminating outlets than on land-terminating glaciers and accelerated retreat from 2000 onwards was linked to sea ice decline. In a further case study, Humboldt Glacier, northern Greenland, retreated rapidly from 1999, coincident with atmospheric warming. However, retreat rates were an order of magnitude greater on its northern section, due to a major subglacial trough, which strongly modulated its response to external forcing. Overall, during the past decade, outlet glacier retreat was widespread and rapid in the Atlantic Arctic. Although some regional-scale patterns of retreat and response to forcing were evident, retreat rates varied markedly. Fjord width variation was identified as an important and widespread control on outlet glacier retreat, which highlights the need to consider glacier-specific factors when forecasting glacier response to climate change.