Mapping Greenland ice sheet velocities at high temporal resolution using satellite based imagery

• Main Author: Lemos, Adriano Gomes De
• Format: Thesis
• Language: English
• Published: University of Leeds 2019
• Subjects: Greenland; Jakobshavn Isbræ; Nioghalvfjerdsfjorden; The Sentinel; glacier; Ice Sheet; Jakobshavn; Jakobshavn isbræ; Petermann glacier
• Online Access: https://etheses.whiterose.ac.uk/24373/; https://etheses.whiterose.ac.uk/24373/1/Lemos_SEE_EarthEnvironment_PhD_2019.pdf

In this thesis, I develop and demonstrate a system for monitoring fluctuations in the speed of Greenland ice sheet outlet glaciers with high temporal frequency from imagery acquired by a range of satellite missions. This work is motivated by an ambition to utilise a new era of operational satellites to better understand how environmental changes are affecting the flow and mass of Greenland’s outlet glaciers. First, I exploited the systematic and frequent acquisition schedule of the Sentinel-1 satellite constellation to track weekly variations in the speed of four fast-flowing, marine-terminating glaciers - Jakobshavn Isbræ, Petermann Glacier, Zachariæ Isstrøm and Nioghalvfjerdsfjorden - between 2015–2017. By combining the Sentinel-1 data with an eight-year time-series derived from TerraSAR-X, I produced a decadal record of variations in glacier flow. On a technical level, I was able to demonstrate the value of Sentinel-1’s 6-day revisit time for glaciology, because it leads to an increase in the degree of correlation between consecutive images and also to improved tracking of movement near to the glacier calving fronts. On a scientific level, I was able to demonstrate that a strong correlation exists between iceberg calving events and glacier speedup, and to show for the first time that Jakobshavn Isbræ has begun to slow down. Next, I assessed the capability of the Sentinel-1 constellation to detect and chart seasonal changes in the speed of five slow-flowing glaciers situated in a 14,000 km2 land-terminating sector of central-west Greenland. These new measurements offer significantly improved spatial and temporal resolution when compared to previous missions, in all seasons. I was able to show that there are marked differences in the degree of seasonal speedup of the five glaciers – with summertime increases in ice flow ranging from 21 to 49 % - reinforcing the need for comprehensive monitoring and the challenges of making regional extrapolations. Thanks to the high temporal frequency afforded by Sentinel-1, I ...