East Greenland firn aquifer water extends the efficiency of the subglacial hydrological system beyond the melt season
Abstract
The state of the Greenland subglacial hydrologic system is sensitive to the quantity and rate of meltwater reaching the glacier bed. In regions with bare ice, meltwater generally reaches the bed rapidly (within hours), which causes daily and seasonal changes in the subglacial drainage system and, in turn, the motion of the overlying ice. Meltwater that collects in firn aquifers, however, likely takes a much longer time to reach the subglacial environment due to its seasonal- to multi-year transit time through the firn and multi-day to month-long hydrofracture through crevasses to the bed. A lack of observations limits our ability to predict the influence of firn-aquifer water on the subglacial hydrologic system once it reaches the bed.
We use the Glacier Drainage System (GlaDS) model to test how water draining from an idealized firn aquifer affects the development of the regional subglacial hydrologic system. We find that firn-aquifer water raises the subglacial water pressure at inland locations, but reduces it downstream via persistent subglacial channelization. Compared to cases without a firn aquifer, water pressure remains higher during winter, which maintains a small channel network overwinter that can accommodate melt more quickly during spring. Overall, the effect of the firn aquifer is to dampen seasonal variations in the subglacial system. These differences are consistent with unexpected seasonal velocity patterns observed at glaciers in the Ikertivaq region of East Greenland, which are ringed by firn aquifers and show a dampened seasonal cycle of ice flow. Our modeling results highlight the importance of firn-aquifer water to subglacial hydrology at a time when surface melt rates and firn-aquifer extent are increasing in East Greenland.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C54A..03P
- Keywords:
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- 0726 Ice sheets;
- CRYOSPHERE;
- 0774 Dynamics;
- CRYOSPHERE;
- 0776 Glaciology;
- CRYOSPHERE;
- 0798 Modeling;
- CRYOSPHERE