Influence of synoptic scale weather variability on ice speed-up events in Southwest Greenland
The Greenland Ice Sheet (GrIS) has experienced increasing ice loss in the past decades and the trend is expected to continue due to climate change. However, large uncertainties about the magnitude of Greenland’s future ice loss remain. One process that contributes to this uncertainty are transient i...
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| Other Authors: | , , , |
| Language: | English |
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ETH Zurich
2021
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| Online Access: | https://hdl.handle.net/20.500.11850/561596 https://doi.org/10.3929/ethz-b-000561596 |
| Summary: | The Greenland Ice Sheet (GrIS) has experienced increasing ice loss in the past decades and the trend is expected to continue due to climate change. However, large uncertainties about the magnitude of Greenland’s future ice loss remain. One process that contributes to this uncertainty are transient ice accelerations, so-called ice speed-up events, caused by a short-term increase in rain-/meltwater, which descends to the glacier bed and can enhance basal sliding. Here, we investigate this phenomenon focusing on two main objectives. First, we present an analysis of local conditions on the Russell glacier in Southwest Greenland, which confirms the importance of meltwater variability for ice speed-up events. We find the strongest influence in early summer with correlations between surface melt and ice velocities above 0.8 in May and identify a typical lag of zero to one day between meltwater peaks and their ice velocity responses. Contrastingly, we find rainfall to have a minor influence with only 4 out of 51 ice speed-up events, where daily increases in water input on the glacier are dominated by rainfall. Secondly, we study the atmospheric drivers of ice speed-up events using a Self-Organizing Maps (SOM) classification of synoptic weather situations over Greenland. Two main patterns that induce most ice speed-up events emerge: The first pattern is characterized by southerly advection of warm and moist air that increases local surface melting by enhanced downward longwave radiation and high sensible heat flux. The second one is a large-scale anticyclone that induces GrIS surface melting through strong downward shortwave radiation and descending air that warm adiabatically. Our study provides new insights into atmospheric drivers of short-term ice accelerations and contributes towards an effort to constrain the impact of ice speed-up events on GrIS mass loss under a changing climate, which can be achieved when more high-resolution ice velocity data is available. |
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