A SAR-derived long-term record of glacier evolution in North-West Greenland

• Main Author: Oost, R. (author)
• Other Authors: Hanssen, R.F. (mentor), Van Leijen, F. (mentor), Vizcaino, M. (mentor), Ditmar, P.G. (mentor)
• Format: Master Thesis
• Language: English
• Published: 2016
• Subjects: glaciers; Greenland; terminus position; climate change; ice sheet; marine-terminating outlet glaciers; outlet glaciers; SAR; amplitude tracing; speckle tracking; glacier; Ice Sheet; Uummannaq
• Online Access: http://resolver.tudelft.nl/uuid:0b124f1a-9821-472c-9496-a94bfb1f2b22

Observations show that the Greenland ice sheet is losing mass with accelerating pace. Ice discharge trough outlet glaciers contributes approximately for half of the mass loss. However, the role of marine-terminating outlet glaciers on the response of the Greenland ice sheet to climate change is relatively unknown. In recent years, observations have shown dramatic changes in the velocity and front position in a number of marine-terminating outlet glaciers, but a questions remains why some outlet glaciers are stable and others are not. Consequently, predictions on the evolution of the Greenland ice sheet are uncertain until a realistic representation of marine-terminating outlet glaciers is possible. More specifically, significant uncertainty exists on the link between climate forcing and marine-terminating outlet glacier behaviour. This link has been associated to glaciers-specific factors, such as bedrock topography and fjord width, but more glaciers need to be studied. Here we present a study that focussed on the response of different glaciers to a similar climate forcing, thereby taking into account their topographic situation. SAR observations of seven marine-terminating glaciers in the Uummannaq-bay (West-Greenland) are used to estimate terminus positions and glacier flow velocity. The observations are acquired between 1991 - 2014 using ERS, Envisat and TerraSAR-X, thereby extending the length of the state-of-the-art records. Terminus positions are manually digitized and an equivalent position is determined on the glacier flowline, a significant improvement with respect to the box-method. Glacier flow velocities are obtained using ICC offset tracking. The estimated offsets of ERS and Envisat image pairs were noisy, but have been filtered using the along-track velocity profile that was accurately estimated with TerraSAR-X image pairs. The results showed that the outlet glaciers in this region have been stable during the 1990's, and that the warm winter of 2003 initiated retreat. Three glaciers (Lille ...