Accurate forecasting of the Greenland Ice Sheet's contribution to global sea-level rise requires detailed knowledge of the processes in action at marine-terminating glaciers and their sensitivity to the controls that govern them. Both ice velocities and supraglacial-melt have increased significantly over the last decade, while recent research suggests that the dynamic ice-loss can be attributed to oceanic rather than atmospheric forcing. Warm, subtropical-originating Atlantic water has been identified as a primary driver of mass loss across the marine sectors of the Greenland Ice Sheet. Subglacial drainage networks inject fresh-water at depth producing a buoyant upwelling at the glacier front, renewing the Atlantic water in contact with the ice and thus enhancing the submarine-melt. To investigate these processes, their mutual forcing, and seasonal variability, a time-series of oceanographic, glaciological, and atmospheric measurements was collected at the front of Store Glacier, a major marine terminating outlet in Uummannaq bay (West Greenland). These data revealed a submarine-melt rate of 1.9±0.5md⁻¹ during winter months, which is five times larger than previous assumptions, and is attributed to the year-round contribution of basal-melt to the subglacial discharge of fresh water. A novel method using repeated 3D scanning of the submerged part of the glacier front permitted us for the first time to directly measure a summer submarine-melt rate of 3.4±0.7md⁻¹. Together, summer and winter submarinemelt contributed to 14% of the annual frontal ablation and up to 25% during summer months. Measurements from inside two upwelling plumes provided insight to their physical characteristics as well as their impact on the entire glacier front. These results highlight the need to reconsider the assumptions used in current model parametrisations of the ocean-glacier interface when evaluating the response of the Greenland-ice sheet to a warmer climate.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:683455 |
| Date | January 2016 |
| Creators | Chauché, Nolwenn |
| Contributors | Hubbard, Alun ; Neal, Mark |
| Publisher | Aberystwyth University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/2160/5d617af0-d905-4924-92a4-5d3d30f32759 |
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