Tidewater glacier mass-loss mechanisms in Northwest Greenland

The Greenland Ice Sheet is currently the leading ice-sheet contributor to sea-level rise. Focused research, starting in the mid 2000’s, has concluded that the two main driving forces of this mass loss are (1) increased surface melting in the ice sheet’s land-terminating southwestern region [Enderlin et al., 2014], and (2) warm, ocean currents in the south-eastern and western regions driving iceberg calving at tidewater-glacier termini [Straneo & Heimbach, 2013].

The Northwest Greenland Ice Sheet (NWGIS) experiences little surface melt and terminates in among the coldest ocean water in all of Greenland. Thus, we would expect some of the lowest rates of mass loss in NWGIS relative to other sectors. What we observe is that NWGIS has contributed the most to sea-level rise of any sector from 1972–2018 [Mouginot et al., 2019]! The magnitude and acceleration of NWGIS mass loss indicates that there are rapid mechanisms for mass loss that we do not yet understand. Targeted research on the NWGIS is required to fill in knowledge gaps on the mechanisms at work in Northwest Greenland, and the mechanisms that lead to ice-sheet mass loss globally.

Most NWGIS mass loss occurs dynamically through calving, but we lack a solid explanation for whether ocean-driven or atmospheric-driven processes cause this mass loss [Slater & Straneo, 2022]. To tackle this knowledge gap, this research project will bring together observations of glacier calving events, modelled estimates of ice-sheet surface runoff, and numerical modelling of the subglacial drainage system to test the hypothesis that NWGIS tidewater glaciers can retreat rapidly under low oceanic thermal forcing, if the basal drainage system releases water in a way that facilitates calving. The hypothesis that we will test contrasts with earlier tidewater-glacier retreat hypotheses that rely on warm ocean currents driving high rates of calving and submarine melting [Straneo & Heimbach, 2013].

Finally, a fundamental challenge in our ability to predict tidewater glaciers’ dynamic, future response to increased atmospheric and oceanic warming is quantifying and understanding mass-loss mechanisms at work today. The work of this research project will fill in our knowledge gap on mass-loss mechanisms at work today, which, in turn, will enhance our ability to predict mass loss for the full Greenland Ice Sheet in future decades.

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