Abstract
Greenlandic glaciers distinct from the ice sheet make up 12% of the global glacierized area and store about 10% of the global glacier ice volume (Farinotti et al., 2019). However, knowledge about recent climate change-induced volume changes of these 19,000 individual glaciers is limited. The small number of available glaciological and geodetic mass-balance observations have a limited spatial coverage, and the representativeness of these measurements for the region is largely unknown, factors which make a regional assessment of mass balance challenging. Here we use two recently released digital elevation models (DEMs) to assess glacier-wide elevation changes of 1,526 glaciers covering 3,785 km2 in west-central Greenland: The historical AeroDEM representing the surface in 1985 and a TanDEM-X composite representing 2010–2014. The results show that on average glacier surfaces lowered by about 14.0 ± 4.6 m from 1985 until 2012 or 0.5 ± 0.2 m yr−1, which is equivalent to a sample mass loss of ~45.1 ± 14.9 Gt in total or 1.7 ± 0.6 Gt yr−1. Challenges arise from the nature of the DEMs, such as large areas of data voids, fuzzy acquisition dates, and potential radar penetration. We compared several different interpolation methods to assess the best method to fill data voids and constrain unknown survey dates and the associated uncertainties with each method. The potential radar penetration is considered negligible for this assessment in view of the overall glacier changes, the length of the observation period, and the overall uncertainties. A comparison with earlier studies indicates that for glacier change assessments based on ICESat, data selection and averaging methodology strongly influences the results from these spatially limited measurements. This study promotes improved assessments of the contribution of glaciers to sea-level rise and encourages to extend geodetic glacier mass balances to all glaciers on Greenland.
Highlights
Greenland’s peripheral glaciers are key indicators of climate change, respond faster to climate change than the Ice Sheet and contribute strongly to sea-level rise (Zemp et al, 2019)
This study presents for the first time glacier-wide elevation changes for a large sample of Greenland’s peripheral glaciers
We found the local mean hypsometric method to be suitable for westcentral Greenland where surge-type glaciers are abundant
Summary
Greenland’s peripheral glaciers are key indicators of climate change, respond faster to climate change than the Ice Sheet and contribute strongly to sea-level rise (Zemp et al, 2019). Glacier Elevation Changes West-Central Greenland of their volume and mass is still poor due to observational gaps. In situ mass-balance measurements on Greenland’s peripheral glaciers exist (e.g., Mittivakkat, Freya and Qasigiannguit glacier, cf WGMS, 2019) and are important for evaluating models and remote sensing data (Machguth et al, 2016) but are limited to a small number of accessible glaciers. The studies by Bolch et al (2013) and Gardner et al (2013) are heretofore the only studies that have estimated volume changes for all glaciers around the Greenland Ice Sheet based on ICESat laser altimetry data from 2003 to 2008 (Bolch et al, 2013) and 2003 to 2009 (Gardner et al, 2013), respectively. ICESat provides precise elevation information at point locations but is challenged in mountainous terrain by non-alignment of repeat tracks, limited coverage, and possible sampling bias with respect to accumulation/ablation distribution of glaciers, which results in high uncertainty ranges
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