Feedbacks between ice dynamics, subglacial discharge, and submarine melting during tidewater glacier retreat
Abstract
Subglacial discharge from tidewater glaciers mixes with warm fjord waters at depth, driving turbulent upwelling plumes that vigorously melt ice. Recent studies suggest that submarine melting can destabilize glacier termini and that plume melt rate increases nonlinearly with subglacial discharge. For land-terminating glaciers, net annual discharge increases during glacier retreat by about 25% due to climate-driven reductions in glacier storage. The situation is different for tidewater glaciers, which are capable of experiencing relatively rapid changes in geometry (i.e., glacier volume and submerged depth of the terminus) that are driven by ice-dynamic feedbacks. Here we couple a 1-D depth- and width-integrated ice flow model to a buoyant plume model as a first step toward assessing feedbacks between glacier dynamics, subglacial discharge, and plume dynamics. For tidewater glacier retreat in a steady climate, our results indicate that (1) net annual subglacial discharge can decrease by about 25% due to a decrease in catchment size, (2) the terminal level of the plume depends most strongly on the submerged depth of the terminus, and (3) the depth- and width-averaged submarine melt rate decreases when the terminus retreats into deep water, whereas the maximum submarine melt rate increases (and vice-versa for retreat out of deep water). Due to uncertainty regarding the impact of submarine melting on iceberg calving, it currently remains unclear whether these variations in submarine melt rates represent negative or positive feedback mechanisms. Nonetheless, we expect that further idealized simulations such as these will provide insights into the variability of plume structure, submarine melting, and consequences for glacier dynamics on decade-to-century time scales.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.C51A0648A
- Keywords:
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- 0720 Glaciers;
- CRYOSPHEREDE: 0728 Ice shelves;
- CRYOSPHEREDE: 4546 Nearshore processes;
- OCEANOGRAPHY: PHYSICALDE: 4562 Topographic/bathymetric interactions;
- OCEANOGRAPHY: PHYSICAL