Ice sheets are vast expanses of ice. The Greenland ice sheet (GrIS) is the second largest ice sheet on Earth at 1.7 million km2 and is currently losing mass at an accelerating rate, contributing ~14 mm to global sea level rise between 1992 and 2020. Understanding the processes driving this mass imbalance is essential for projecting ice sheet evolution. This thesis explores methods for studying key GrIS processes using digital elevation models (DEMs), focusing on supraglacial lake depth estimation, floating ice tongue identification, and grounding line delineation. Chapter 4 assesses the use of DEMs for measuring supraglacial lake depth, comparing ArcticDEM and ICESat-2 LiDAR-derived bathymetry with estimates from the radiative transfer equation (RTE) applied to Sentinel-2 imagery. While elevation-based methods agree strongly (r = 0.98), RTE-derived depths show large biases and uncertainties with the green band overestimating depths by ≤ 153% and the red band underestimating depths by ≤ 63%. This highlights limitations in current optical approaches, demonstrating the value of multi-sensor validation for improving volume estimates. Chapter 5 introduces an approach for identifying floating ice tongues using DEM deviation analysis across fifteen northern Greenland glaciers. The method identifies floating ice signatures on five lobes, confirms the absence of signatures on eight, and suggests ambiguous signatures on two. This provides a proof-of-concept that DEMs can be used to dynamically locate floating ice signatures. Chapter 6 combines ArcticDEM with a tidal model to detect timestamped grounding lines based on tidal flexure. This method yields > 200 new grounding line estimates across three major glaciers, identifying a previously undocumented 3.45 km² ice tongue on one of these glaciers as of 2018. These studies provide new tools for monitoring ice sheet processes, and their findings will support future research into the impact of climate change on our ice sheets and their stability.
Laura Melling (Thu,) studied this question.