Investigating tidewater glacier and iceberg submarine melting in Greenland’s fjords

• Main Author: Moyer, Alexis Noelle
• Other Authors: Nienow, Peter, Sole, Andrew, Gourmelen, Noel, Bingham, Robert, other
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: The University of Edinburgh 2019
• Subjects: glaciology; remote sensing; Greenland Ice Sheet; submarine melt rate; tidewater glacier; Greenland; glacier; Ice Sheet; Tidewater
• Online Access: http://hdl.handle.net/1842/35876

Accelerated mass loss from the Greenland Ice Sheet in recent decades has been concentrated around the coastal margins, where glacier ice fronts and the undersides of floating ice are in contact with warm ocean waters. The interaction of the ice sheet with a warming ocean leads to thinning of tidewater glaciers, which has been linked to increased glacier velocity, calving, retreat and subsequent mass loss. Our understanding of these ice-ocean interactions is limited, particularly regarding submarine melting of tidewater glacier ice fronts, which has been proposed as an initial trigger for glacier retreat and acceleration. Understanding the mechanisms promoting changes to tidewater glacier dynamics is critical, as they are currently absent from ice sheet models and present a large source of uncertainty in 21st century sea level rise predictions. This thesis develops two novel remote sensing techniques, to investigate both submarine melt rates under tidewater glacier floating ice tongues and iceberg freshwater fluxes from submarine melting, providing improved datasets and process understanding that can be used to constrain changes to the Greenland Ice Sheet in a warming world. The first result of this thesis is the development of a methodology to estimate submarine melting under floating ice tongues using satellite imagery. Submarine melt rates were derived by differencing along-flow ice tongue surface elevation, in combination with ice tongue velocity and changes in surface mass balance. Kangiata Nunaata Sermia (KNS), a large tidewater glacier in southwest Greenland, was used as a proof-of-concept study site. Mean submarine melt rates under the seasonal ice tongue at KNS in spring 2013 reach over 0.8 ± 0.3 m d−1, decreasing with distance down-fjord from the glacier grounding line and varying across-fjord. These variations in melt rate likely result from changes in ice tongue draft and fjord water temperature with depth, but may also reflect the strength of subglacial discharge plumes exiting beneath the glacier ...