Abstract
Changes in the calving front position of marine-terminating glaciers strongly influence the mass balance of glaciers, ice caps, and ice sheets. At present, quantification of frontal position change primarily relies on time-consuming and subjective manual mapping techniques, limiting our ability to understand changes to glacier calving fronts. Here we describe a newly developed automated method of mapping glacier calving fronts in satellite imagery using observations from a representative sample of Greenland’s peripheral marine-terminating glaciers. Our method is adapted from the 2-D wavelet transform modulus maxima (WTMM) segmentation method, which has been used previously for image segmentation in biomedical and other applied science fields. The gradient-based method places edge detection lines along regions with the greatest intensity gradient in the image, such as the contrast between glacier ice and water or glacier ice and sea ice. The lines corresponding to the calving front are identified using thresholds for length, average gradient value, and orientation that minimize the misfit with respect to a manual validation data set. We demonstrate that the method is capable of mapping glacier calving fronts over a wide range of image conditions (light to intermediate cloud cover, dim or bright, mélange presence, etc.). With these time series, we are able to resolve subseasonal to multiyear temporal patterns as well as regional patterns in glacier frontal position change.
Highlights
G LACIER mass loss and thermal expansion are the two largest contributors to contemporary sea level rise, which critically impacts the coastal populations [13]
Images were analyzed over the Landsat 8 record (2013–2020) available from the US Geological Survey (USGS) on the Amazon Web Services (AWS) cloud
Images where there are shadows cast by the fjord walls across the glacier terminus and where there are shadows from the ice cliff at the calving front remain challenging to delineate using this method
Summary
G LACIER mass loss and thermal expansion are the two largest contributors to contemporary sea level rise, which critically impacts the coastal populations [13]. Global sea level rise is of major concern to the coastal systems, with many communities focusing on the infrastructure adaptations [13]. Estimates of global sea level rise will be critical to risk assessment and the development of adaptation strategies. The fresh water flux associated with glacier mass loss directly impacts marine ecosystems and regional ocean circulation. Ice mass loss from Greenland’s glaciers, ice caps, and ice sheet contributes ∼43% to the contemporary global sea level rise [30]. The Greenland ice sheet, the largest contributor to sea level rise in the twenty-first century [18], was responsible for an average of ∼0.47 ± 0.23 mm · yr−1 of sea level rise over 1991–2015 [38]
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