The response of marine-terminating outlet glaciers in northwestern Greenland to recent and near-future climate change

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Summary of proposed projectThe Greenland Ice Sheet has experienced increased mass loss since the 1990s, resulting in an estimated global sea level rise of 10.8 0.9 mm from 1992-2018. Mass loss has occurred through increased surface melting and enhanced ice discharge at the ice-fronts of marine-terminating outlet glaciers, which are fast-flowing conveyor belts of ice that drain the ice sheet. Arctic air temperatures are projected to rise by up to 8 C by 2100, which are likely to further increase ice discharge from marine-terminating outlet glaciers and contribute significantly to near-future sea level rise. Nevertheless, there are fundamental gaps in our understanding of the factors controlling ice discharge. Increases in ice discharge were initially concentrated in southeastern Greenland during the early 2000s. However, since 2005 accelerated ice discharge from marine-terminating outlet glaciers has begun in the northwest, with rapid acceleration, retreat and thinning occurring throughout the region. Despite this, only a limited number of regional studies, many of which have been spatially and/or temporally constrained, have been conducted in northwestern Greenland to understand the mechanisms controlling its recent dynamic change, with sub-annual variations in glacier behaviour particularly understudied. Therefore, the extent to which current changes in glacier behaviour are being forced by atmospheric and oceanic forcing or are the result of glacier-specific factors such as the topography of the glacier bed remains unclear. This project aims to use remotely sensed data to extend previous studies (e.g. Carr et al. 2013b; Moon et al. 2015) spatially and temporally to assess recent seasonal changes in terminus position, velocity and surface elevation at marine-terminating outlet glaciers in northwestern Greenland and determine the mechanisms controlling their recent and near-future behaviour. It will address the following research questions:1. How have the seasonal terminus positions, velocities and surface elevations of marine-terminating outlet glaciers in northwestern Greenland evolved and how does this vary spatially?2. To what extent does sea ice control marine-terminating outlet glaciers dynamics, and how does this vary with the different fjord configurations and sea ice characteristics?3. What are the seasonal velocity patterns of northwestern Greenland's glaciers, and what are their primary controls?4. How might northwest Greenland glaciers behave in the future, and to what extent could this be influenced by their basal topography?To address these questions, seasonal glacier velocities will be obtained from the MEaSUREs Project to assess changes in ice velocity, high resolution Landsat 8 and Sentinel-2 satellite imagery will be used to measure variations in terminus position, and ICESat and Arctic DEM data will be acquired to assess surface elevation changes. The influence of sea ice and ice mélange (weak seasonal ice shelf) upon seasonal glacier dynamics will be examined from US National Ice Centre Charts and by categorising the rigidity of sea ice/ice mélange at the glacier termini from satellite imagery. Following this, surface runoff measurements from RACMO2.3p2 and seasonal terminus positions will be analysed to determine their influence upon seasonal glacier velocities throughout the region. In the final stages of the project, the Úa finite-elemental ice-flow model will be used to assess the future sensitivity of marine-terminating outlet glaciers to climate change, with focus given to the influence of basal topography. Overall, this project seeks to further the scientific understanding on how northwestern Greenland's marine-terminating outlet glaciers have responded to recent climate change, determine which forcing mechanisms are primarily controlling their behaviour and estimate how the region's glaciers may respond to near-future climate change.