Investigating North Greenland ice shelves and their response to warming climate

Abstract

The Greenland Ice Sheet has been losing mass at an increasingly rapid pace since the mid 1990s, which is forecast to accelerate further into the coming century. This mass loss is translated directly into global mean sea level rise, with severe consequences for coastal communities around the world who will rely on accurate predictions of sea level contributions to prepare for and mitigate the resultant effects. A significant source of uncertainty in models which predict sea level rise is the response of ice shelves and their grounding lines to environmental forcing. Ice shelves are critical components to understand because they exert a buttressing effect on upstream ice, preventing it from discharging rapidly to the ocean through exerting a back stress on glaciers which would otherwise be free to accelerate, thin, and increase output of mass to the ocean in response to a warming climate. This study quantified changes to ice shelf areas in North Greenland between 1995 and 2016 with the aim of understanding vulnerability to increasing ocean temperature and ice shelf runoff in the region. This was achieved through the measurement of annual average terminus position through repeat digitisation of ice shelf margins in GEEDiT, a tool developed by Lea (2018), which were then integrated with linearly interpolated grounding lines from the ESA’s Climate Change Initiative project, which measured grounding line positions in the late 1990s and 2017 across North Greenland. The ice shelf areas of Petermann Gletsjer, Ryder Gletsjer, Hagen Brae and Nioghalvfjerdbræ were found to have changed by - 27%, -8%, +28%, and +180% respectively. A secondary aim was to understand whether a linear relationship between environmental forcing variables and terminus positions exists at these ice shelves, which has previously been identified by Cowton et al. (2018) at tidewater glaciers. It was established that a direct linear co-integration is not applicable to ice shelf environments, which consequently increases concern that current approximations of linear forcing used in sea level predictions are severely limited. This is because local geometry and bathymetry play a strong role in modulating the delivery of heat to ice shelf environments.