Massive river suspected under Greenland’s ice sheet | Polarjournal
The Petermann Glacier, named after the German geographer August Petermann, has been the focus of science for a long time. In 1962, 2010 and 2012, gigantic parts of the glacier tongue (back) broke off and drifted down the West Greenland coast as icebergs. Picture: A. Münchow / AWI

The Petermann Glacier in northwest Greenland has made the headlines several times in recent years because, on the one hand, an iceberg of twice the size of Manhattan had detached from its 70-kilometer-long tongue in 2012. It was also revealed last year that its flow speed had accelerated to more than 1 kilometres per year. But even what lies beneath the glacier seems to be record-breaking. Model simulations by two US researchers at Hokkaido University suggest that a huge river could hide beneath the ice sheet and glacier.

The modelling concludes that the long valley in northwest Greenland, already known by radar data, could extend to the middle of the ice sheet and would not consist of segments, as previously assumed, but would be open completely. This would have great consequences for the meltwater that flows under the ice in this valley and the outflow. This is because it would reach the coast virtually unhindered and pour into the Hall Basin, which lies under the Petermann Glacier Tongue, at a depth of around 500 metres. Christoper Chambers, the lead author of the study, says: “The results (compeltely mathematical, ed.) are consistent with a long subglacial river.” The results of the study, which also involved researchers from the Universities of Oslo and Utrecht, have now been published in the journal The Cryosphere.

Two of the study’s authors, Christopher Chambers (left) and Ralf Greve (right), are working at the University of Hokkaido and used mathematical models to examine NASA’s 2013 radar data in more detail and found that the valley is likely to go far inland underneath the ice sheet to the coast without interruption, which could cause a river to exist under the ice. Picture left: Chamber et al, 2020 / right: Ralf Greve

The result of the simulation not only has possible consequences for the underground of Greenland, but also for the flow speed of the glacier, which had increased in recent years. An earlier study by the Alfred Wegener Institute had shown that melting of the surface had caused the braking force at the edges to be lost. If there was a huge river under the ice as well, this could mean additional acceleration. But Chambers warns against hasty conclusions: “Considerable uncertainty remains. 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.” Ralf Greve, who developed the model, also says: “Additional radar surveys are needed to confirm the simulations are accurate. This could introduce a fundamentally different hydrological system for the Greenland ice sheet.” The results of the simulation then could help to better model the behaviour of the ice sheet under different conditions and thus allow more precise statements regarding the effects of climate change.

The Petermann Glacier is located in the northwest corner of Greenland and covers an area of about 1,300 square kilometers. Its prominent ice tongue is almost 70 kilometres long. At its grounding line, the glacier is almost 600 meters thick, while the tongue still has 30 – 80 meters. The glacier flows into the fjord of the same name and then into the Nares Strait. In 2010, the largest known iceberg to date with an area of 260 square kilometres, had calved here.

Dr Michael Wenger, PolarJournal

Link to the study: Chambers, C., Greve, R., Altena, B., and Lefeuvre, P.-M.: Possible impacts of a 1000 km long hypothetical subglacial river valley towards Petermann Glacier in northern Greenland, The Cryosphere, 14, 3747–3759,, 2020.

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