Spatial Patterns of Submarine Melt and Basal Crevasse Growth on Greenland Ice Tongues

Submarine melting is a direct mechanism by which oceans influence outlet glaciers, and can significantly modulate both grounding line and calving dynamics. Similarly, basal crevasse evolution likely provides a first-order control on iceberg calving for most glaciers with a floating, or loosely floating, terminus. However, converse to iceberg calving which has substantial long-term records due to advancements in satellite remote sensing, both basal melt and crevasse growth remain poorly quantified and sparsely documented over extensive temporal and spatial scales. While recent studies report large-scale basal melt rates through a variety of remote sensing methods, few studies differentiate between 1) fracture versus melt of basal crevasses, and 2) spatial variability in basal melt rates beneath floating ice tongues. To better model the response of marine-terminating glaciers (MTGs) to anthropogenically-induced climate change, we need to quantify these key metrics of ice-ocean interactions.

Here, we present updated results of multi-annual basal melt rates and basal crevasse growth derived from NASA Operation IceBridge (OIB) and the Center for Remote Sensing of Ice Sheets (CReSIS) radar depth sounder (RDS). Our pre-processing methodology includes: semi-automated layer tracking using a Viterbi algorithm, echogram projection and resampling onto a master profile, and velocity corrections based on NSIDC MEaSUREs annual ice flow velocity maps. We present changes to ice shelf and individual crevasse geometry between 2010 to 2019 for a total of 7 glaciers in North Greenland (Petermann Glacier, Nioghalvsfjerdbræ (79N Glacier), Humboldt Glacier, Ryder Glacier, Steensby Glacier, and Zachariæ Isstrøm). For all glaciers we compare echograms from repeat passes over central flowlines and, where available, extend our comparison to the glacier margins. Results from this study will enhance the community's current understanding of ice-ocean relationships by providing new information into both spatial trends in basal melt and of basal crevasse evolution through stepwise documentation of shelf and feature growth.