Elevation and volumetric changes to the Greenland ice sheet derived from Sentinel-3 satellite radar altimetry

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)

Abstract

The European Space Agency (ESA) has been operating satellite radar altimeters over the ice sheets since the launch of the European Remote Sensing (ERS) satellites in 1991. Radar altimeters monitor ice sheet evolution and enable estimates of ice sheet mass balance, important for assessing the land ice contribution to global sea level rise. Problematically, an observation gap may occur in the elevation record from the mid-2020s onwards in between cryosphere specific missions, CryoSat-2 (CS2) and CRYSTAL. This thesis explores the glaciological applications of Sentinel-3 (S3), a marine focused
radar altimeter mission, to fill the gap in the radar altimetry time series of elevation change over the Greenland ice sheet.

First, the capacity of S3 to monitor glaciological processes is assessed through validation with airborne laser altimetry records. The accuracy, precision, and coverage of ice sheet elevation provided by S3 is determined over Greenland and compared to CS2 to establish the continuity between the two missions. Rates of elevation change of the Greenland ice sheet derived from S3 are presented over a 3-year period from January 2017 − January 2020. Here, S3A is shown to provide spatially consistent, robust rates of elevation change, in the ice sheet interior. However, coverage decreases where the elevation product degrades with increased surface slope around the margins of the ice sheet. Good agreement is found between mapped rates of elevation change determined from S3 and CryoSat-2 both spatially and in magnitude. Volume estimates are also obtained from S3 and found to be reliable in areas of high spatial sampling, but are inconsistent with volume estimates determined from CS2 for the ice sheet exterior. Finally, we assess the capability of S3 to determine interannual and seasonal variability of ice sheet elevation change, utilising S3’s 27-day repeat cycle. A monthly time series of the elevation change is produced over the interior of the ice sheet from January 2017 − January 2020, a period containing years of anomalous accumulation (2017, 2018) and melt (2019). It is demonstrated that S3 can resolve meteorological signals by mapping spatial and temporal variations in elevation change. Ultimately, this thesis demonstrates the ability of S3 to continue the ice sheet elevation record of radar altimeters, and provides advances in the quantification of high-temporal variations of radar derived elevation change.
Date of Award22 Mar 2022
Original languageEnglish
Awarding Institution
  • University of Bristol
SupervisorJonathan L Bamber (Supervisor) & Jack C Landy (Supervisor)

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