A possible subterranean river flows from the deep interior of Greenland to Petermann Fjord, suggests a paper published in The Cryosphere.
A possible subglacial valley and river deep below the surface of Greenland. Image credit: Chambers et al., doi: 10.5194/tc-14-3747-2020.
“The Greenland bedrock data indicate that a subglacial valley extends from Petermann Fjord into the center of Greenland,” said lead author Dr. Christopher Chambers, a researcher in the Institute of Low Temperature Science at Hokkaido University, and colleagues.
“The valley is segmented along its route in the current bed topographic datasets used in ice sheet simulations.”
“The rises occur where data are interpolated to fill in gaps between where radar has obtained reliable data. This suggests that the valley rises may not be real.”
Dr. Chambers and co-authors wanted to explore what might happen if the subglacial valley is open and melting increases deep in Greenland’s interior known for melting.
The scientists ran numerous simulations to compare water dynamics in northern Greenland with and without valley segmentation
Their results show a dramatic change in how water melting at the base of the ice sheet would flow, if the valley is indeed open.
A distinct subglacial watercourse runs all the way from the melting site to Petermann Fjord, which is located more than 1,000 km (621 miles) away on the northern coast of Greenland.
The watercourse only appears when valley segmentation is removed; there are no other major changes to the landscape or water dynamics.
“The results are consistent with a long subglacial river, but considerable uncertainty remains,” Dr. Chambers said.
“For example, we don’t know how much water, if any, is available to flow along the valley, and if it does indeed exit at Petermann Fjord or is refrozen, or escapes the valley, along the way.”
If water is flowing, the model suggests it could traverse the whole length of the valley because the valley is relatively flat, similar to a riverbed. This suggests no parts of the ice sheet form a physical blockade.
The simulations also suggested that there was more water flow towards the fjord with a level valley base set at 500 m (1,640 feet) below sea level than when set at 100 m (328 feet) below.
In addition, when melting is increased only in the deep interior at a known region of basal melting, the simulated discharge is increased down the entire length of the valley only when the valley is unblocked.
This suggests that a quite finely tuned relationship between the valley form and overlying ice can allow a very long down-valley water pathway to develop.
“Additional radar surveys are needed to confirm the simulations are accurate,” said co-author Dr. Ralf Greve, also from the Institute of Low Temperature Science at Hokkaido University.
“This could introduce a fundamentally different hydrological system for the Greenland ice sheet.”
“The correct simulation of such a long subglacial hydrological system could be important for accurate future ice sheet simulations under a changing climate.”
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C. Chambers et al. 2020. Possible impacts of a 1,000 km long hypothetical subglacial river valley towards Petermann Glacier in northern Greenland. The Cryosphere 14: 3747-3759; doi: 10.5194/tc-14-3747-2020
