Ice dynamics of Greelandic tidewater glaciers at large and small spatio-temporal scales
University of Liverpool, 2021
Online
Hochschulschrift
Zugriff:
Tidewater glaciers (TWGs) in Greenland have experienced widespread retreat and thinning over the past decades as a response to a warming climate. The majority of studies focused on investigating individual and regional TWG behaviour over varying temporal scales and have provided crucial insights into the ice dynamics of TWGs. However, there are still gaps in our understanding of ice sheet wide TWG behaviour over long temporal scales in response to climate, and ice dynamics of TWGs over seasonal to sub-daily temporal scales. This thesis aims to contribute to improve our knowledge of ice sheet-wide multi-decadal TWG behaviour in the context of climate by utilising newly available processing chains, and of individual TWG dynamics by using high spatial resolution PAZ Satellite Aperture Radar (SAR) and high temporal resolution time lapse imagery. The large-scale, multi-decadal study shows that TWG terminus advance/retreat behaviour over regional and GrIS-wide scales is linear, which contrasts the heterogeneous behaviour of individual TWGs. In addition, the results show that regional increases in ice discharge can be accounted for by only 11 TWGs, thereby indicating that TWG retreat does not necessarily equates to increased ice discharge. Individual TWG behaviour was investigated at Narsap Sermia, a TWG in SW Greenland, located ~100 km from the capital Nuuk. The analysis of strain rates derived from high spatial resolution SAR data (1 metre) provide insights into the relationship between local strain extrema and bedrock topography and puts the seasonal evolution of strains into context with climate and environmental forcings. The results further demonstrate that ice damage and crevasse depth are likely to be underestimated when using widely available medium resolution velocimetry products, which has implications for numerical models that use the crevasse-depth calving criterion to simulate individual calving events. Multiple near-terminus short-term ice flow acceleration events were identified from sub-daily time lapse imagery and they could prime the glacier for terminus retreat. We further find higher flow velocities in 2019 compared to the previous years that are not offset by a winter slow down as well as an increase in calving size between 2018 and 2019. This suggests that Narsap Sermia is currently adjusting to changes in climate or boundary conditions, which could lead to terminus retreat and increases in ice discharge with potential implications for Nuuk and its port. The results presented in this thesis provide new insights into regional TWG behaviour and drivers thereof, and the relationship between individual TWG dynamics and subglacial hydrology and bedrock topography, and into short-term ice dynamics in the context of environmental forcings. This thesis thereby contributes to closing current knowledge gaps in glaciology.
Titel: |
Ice dynamics of Greelandic tidewater glaciers at large and small spatio-temporal scales
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Autor/in / Beteiligte Person: | Fahrner, Dominik |
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Veröffentlichung: | University of Liverpool, 2021 |
Medientyp: | Hochschulschrift |
DOI: | 10.17638/03163231 |
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