Brief communication: Glacier run-off estimation using altimetry-derived basin volume change: case study at Humboldt Glacier, northwest Greenland

Laurence Gray

doi:10.5194/tc-15-1005-2021

Abstract

Abstract. CryoSat can provide temporal height change around the Greenland Ice Sheet including that close to the terminus of many glaciers. Height change from the northern outlet of the Humboldt Glacier in northwestern Greenland is combined with ice flux into and out of sections of the glacier basin to derive the water run-off each year from 2011 to 2019. The cumulative 9-year run-off for this part of the Humboldt basin is 9.6±2.9 km3 and is predominantly sub-glacial at the terminus, with large run-offs occurring in 2012, 2015, and 2019 and much smaller ones in 2013, 2016, 2017, and 2018.

Highlights

The recent 21st century increase in mass loss from the Greenland Ice Sheet (Mouginot et al, 2019; The IMBIE team, 2020; Smith et al, 2020) has emphasized the need for regular monitoring of the periphery of the ice sheet, the area which has been, and still is, changing the most rapidly
The interferometric mode on the European Space Agency (ESA) CryoSat satellite was developed in part to alleviate the problems associated with measuring glacial ice height with radar altimeters when surface slopes are relatively large, e.g. at the periphery of the Greenland Ice Sheet
Greenland outlet glacier termini are almost always in a local topographic low such that the “point of closest approach” (POCA) for a satellite radar altimeter pass across a glacier terminus is often displaced to adjacent higher-elevation terrain

Summary

Introduction

The recent 21st century increase in mass loss from the Greenland Ice Sheet (Mouginot et al, 2019; The IMBIE team, 2020; Smith et al, 2020) has emphasized the need for regular monitoring of the periphery of the ice sheet, the area which has been, and still is, changing the most rapidly. Greenland outlet glacier termini are almost always in a local topographic low such that the “point of closest approach” (POCA) for a satellite radar altimeter pass across a glacier terminus is often displaced to adjacent higher-elevation terrain. This effect coupled with the larger slopes and rough surfaces means that it is difficult to measure the height or height change of glacier termini reliably with the traditional radar altimetry technique, i.e. the estimation of the time of arrival of the first radar returns. This suggests that “swath mode” processing (Gray et al, 2013), which uses the part of the waveform beyond the POCA, may be preferable for estimating the height change in these regions

Results

Discussion

Conclusion