Dissertations and Theses

Date of Award

2019

Document Type

Thesis

Department

Earth and Atmospheric Sciences

First Advisor

Kyle McDonald

Second Advisor

Nick Steiner

Third Advisor

Nir Krakauer

Keywords

Glaciers, imaging radar, microwave remote sensing, climate change, hydrology, melt detection, cryosphere

Abstract

Hindu Kush Himalayan (HKH) glaciers serve as some of the most sensitive indicators of changes in global climate. These glaciers shape the hydrologic dynamics of river systems supplying freshwater to over 2 billion people throughout Asia and regulate the geochemistry of sensitive aquatic alpine ecosystems. As snowmelt onsets sooner, lasts longer, and snowfields retreat due to increases in global temperature, the hydrologic dynamics of catchments draining HKH threaten to change the availability of surface freshwater resources for nearly one fifth of the global population, disturb sensitive aquatic habitat, and precipitate hazards associated with glacier wasting. Informed planning and decision-making around adaption to a changing climate requires operational monitoring of glacier melt dynamics to improve study of predicted disturbances to HKH hydrologic systems. This research presents a method for spatially resolved alpine glacier melt detection using synthetic aperture radar (SAR) time series. Building on research into melt detection from passive microwave scatterometers over large ice sheets, this study detects melt characteristics from Sentinel-1 SAR backscatter intensity time series over glacier surfaces using a classification threshold based on a decrease in backscatter intensity relative to average values across the frozen season. Statistical analysis of the radiometric response to dielectric loss on glaciated area within the study region (70,789 km2) shows that cross-polarized melt classification accounts for 24% more of glacier surface area than co-polarized observations. Illustrative comparison of melt classification results to optical imagery captured near the end of seasonal melt reveals that dual polarized melt measurements are concentrated within areas of apparent glacier accumulation yet cross-polarized melt detection occurs more homogeneously across glacier surfaces relative to co-polarized observations. The results of this study suggest that physical characteristics of the glacier surface may be radiometrically distinct across positive and negative zones of glacier mass balance. Improvements to radiometric terrain correction of SAR data in complex high mountain terrain would improve the accuracy of temporal thresholding algorithms for melt detection.

Available for download on Saturday, May 30, 2020

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