Date of Award

Summer 6-10-2023

Document Type

Thesis (Master's)

Department or Program

Earth Sciences

First Advisor

Robert Hawley

Second Advisor

Jonathan Chipman

Third Advisor

Erich Osterberg

Abstract

Geodetic surface mass balance calculations regularly rely on satellite radar altimeters such as CryoSat-2 to understand elevation and volume changes of the Greenland Ice Sheet (GrIS). However, the impact of changing GrIS shallow subsurface stratigraphic conditions on CryoSat-2 elevation products is poorly understood. We seek to investigate the long-term impacts of changing surface and shallow subsurface conditions on CryoSat-2 Level 2 elevation products derived from the Offset Center of Gravity (OCOG), Ocean - Customer Furnished Item (CFI), and University College London (UCL) Land-Ice retracking algorithms through the analysis of radar waveform characteristics. We further investigate time series from 2010 to 2021 of Leading-Edge Width (LeW), Riemann Sum Integral (RSI), and Trailing-Edge Slope (TeS) metrics calculated from Level 1B CryoSat-2 radar waveforms. We use Bayesian Model averaging and changepoint detection to compare equivalent time series in elevations derived from CryoSat-2’s three retracking algorithms. This workflow is performed at five GrIS locations representing different glaciological regimes and compared with previous literature. We note that melting events, snowpack recovery, and potentially anomalous snow accumulation and high-speed winds are evident in GrIS dry snow zone Level 1B LeW time series. We determine that Level 1B LeW has an inverse relationship with the model-based retracked Level 2 elevations. Future work is needed to understand the impacts varying GrIS snow accumulation rates and high-speed wind events on the elevation products, as well as to create retracking algorithms that are more resistant to abrupt changes in the shallow subsurface.

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