Feedbacks Between Fjord Circulation, Mélange Melt, and the Subglacial Discharge Plume at Kangerlussuaq Glacier, East Greenland

Abstract

In recent decades, the Greenland ice sheet has been losing ice and contributing substantially to global sea level rise. Approximately half of this recent loss is due to glacier acceleration, increasing the calving of icebergs into the ocean. This process has been linked with increased ocean heat content on the continental shelf, yet the pathways delivering this heat into Greenland's fjords and its interactions with fjord-scale processes modulating glacier ice loss are still unclear. In this study, we use a series of numerical ocean model configurations to examine feedbacks between ocean circulation, subglacial discharge, submarine glacier melt, and ice mélange in Kangerlussuaq Fjord—a major fjord system where Greenland's third-largest glacier terminates. We find that subglacial discharge is a major control on ocean properties, increasing the up-fjord advection of deep warm water more than 10-fold over fjords without discharge and modulating ocean temperature on the continental shelf near the fjord mouth. Further, discharge-driven upwelling increases ice mélange melt 3-fold, revealing that subglacial discharge is an important control on mélange melt, particularly in the summer when submarine glacier melt and subsequent glacier retreat is highest. These results suggest that subglacial plume activity contributes to the strong correlation between mélange thickness and retreat noted in previous studies and may contribute to extensive future retreat at Kangerlussuaq Glacier.