Geodetic measurements of present-day climate changes in Greenland

• Main Author: Dahl-Jensen, Trine S.
• Format: Book
• Language: English
• Published: Technical University of Denmark 2022
• Subjects: Greenland; glacier; Sea ice; Thule
• Online Access: https://orbit.dtu.dk/en/publications/856ff099-3f56-4139-b627-275f696282c0; https://backend.orbit.dtu.dk/ws/files/310374467/PhD_Thesis_final_Trine_S_Dahl_Jensen.pdf

Global mean sea level has been rising about 3 mm/yr since 1993 due to global warming. Today, Greenland is the largest mass contributor to global mean sea level rise and has been so since the early 2000s. In order to study the movement of the bedrock in response to ice mass loss a network of permanent GNSS stations was developed along the coast of Greenland in 2007-2009. The network (GNET) gives valuable insights into the dynamics and mass loss of nearby glaciers as the uplift decreases rapidly with the distance to the station. During the last decade or so a method called GNSS interferometric reflectometry (GNSSIR) has been developed using GNSS data to study the surrounding environment. It utilizes the interference between the direct signals and the signals reaching the antenna after being reflected off a surface. In the first study of this thesis we test the use of GNSS-IR for studies of inter annual sea level variations in Thule, Greenland, using the existing THU2 GNSS station from 2008 - 2019. We find that the two methods show much of the same sea level variations but also that there are differences significantly larger than the estimated errors. We suggest that the difference are likely a result of a combination of factors; sea ice will affect the two measurements differently and induce an error which is not accounted for, the tide gauge is not datum controlled and the tide gauge was moved to a new location in 2015. For the second study we use a GNSS station which was installed at the PROMICE automatic weather station, NUK-K, in March-August 2020. The aim of the installation was to test if the setup could be used for high precision positioning with the goal of tracking glacier flow. We use the GNSS data from the station to extract snow heights using GNSSIR and compare the results to a sonic ranger mounted on the weather station. Though the data is limited, we find a good correspondence between the GNSS-IR results and the sonic ranger. We suggest that the deviations during some of the melt period is due to the ...