Quantifying ice-shelf basal melt and ice-stream dynamics using high-resolution DEM and GPS time series

• Main Author: Shean, David
• Other Authors: Joughin, Ian R
• Format: Thesis
• Language: English
• Published: 2016
• Subjects: glaciology; ice sheet; photogrammetry; stereo; Remote sensing; Geophysics; Geographic information science and geodesy; earth and space sciences; Pine Island Glacier; Antarc*; Antarctica; Ice Sheet; Ice Shelf; Pine Island
• Online Access: http://hdl.handle.net/1773/36365

Thesis (Ph.D.)--University of Washington, 2016-06 This dissertation describes methods to generate high-resolution digital elevation models (DEMs) of the Earth's ice sheets, and combines these observations with in situ GPS measurements to study basal melting beneath the Pine Island Glacier ice shelf, Antarctica. Pine Island Glacier (PIG) is currently losing mass at a rate of ~40 Gt/yr and contributing ~0.1 mm/yr to global sea level rise. This mass loss has been attributed to rapid retreat, speedup, thinning, and increased discharge in recent decades, due to ocean forcing and/or internal instability. The automated, open source NASA Ames Stereo Pipeline (ASP) was adapted to generate digital elevation models (DEMs) and orthoimages from very-high-resolution (VHR) commercial imagery. I outline a processing workflow for ~0.5 m ground sample distance (GSD) DigitalGlobe WorldView-1/2/3 stereo image data. Output DEM products are posted at ~2 m with direct geolocation accuracy of <5.0 m CE90/LE90. An automated co-registration workflow reduces absolute vertical and horizontal error to <0.5 m, with observed standard deviation of ~0.1-0.5 m for overlapping, co-registered DEMs. I processed all available 2010-2015 WorldView/GeoEye DEMs over the PIG ice shelf, and integrated with other available 2002-2015 DEM/altimetry data. I analyzed Eulerian elevation change (dh/dt) over grounding zones and upstream ice, and developed novel Lagrangian elevation change (Dh/Dt) methodology for elevation measurements over floating ice. I combined these results with an annual mass budget analysis to quantify the spatial and temporal evolution of ice shelf baasal melt. This analysis reveals the complex spatial/temporal evolution and interconnection of grounding zones, sub-shelf cavity geometry, basal melt rates, and upstream dynamics over grounded ice. Rapid PIG grounding line retreat ended between ~2008-2009, followed by the ephemeral regrounding of ~2-3 deep keels as a positive ice shelf thickness anomaly advected over a seabed ridge. ...