Streams of fast-moving ice that extended into the northeastern Greenland Ice Sheet stopped and were abruptly reconfigured thousands of years ago, according to a study published in Nature Geoscience. The findings may help inform our understanding of the stability of the Greenland Ice Sheet under future climate scenarios.
Ice accumulated from snowfall in the interior of Greenland generally moves towards the coast, partly via quickly-moving conduits called ice streams. Along with direct surface melting, this is one of the primary ways in which mass is lost from the ice sheet. The Northeast Greenland Ice Stream is a prominent example that drains a large sector of the current Greenland ice sheet. Despite the importance of ice streams in understanding the overall behaviour of this and other ice sheets, it is unclear exactly why they occur and how stable they are through time.
Steven Franke and colleagues analysed radar data to trace layers buried deep in the northeastern Greenland Ice Sheet, which were then used to reconstruct past ice flow regimes in the region. They found a series of prominent folds indicative of quickly flowing ice to the north of the current Northeast Greenland Ice Stream. The orientation of the folds, as well as the ways they have been deformed, indicate the existence of at least two ice streams that are no longer active. Although it is difficult to assign exact ages to these features, the authors suggest they were active at least into the early Holocene (around 11,500 years ago), and that they drained areas further north than the modern ice stream.
The precise cause of the shift in ice stream locations is unknown, but the authors conclude that Greenland ice streams can rapidly adjust to shifting glaciological conditions and that ongoing warming might lead to similar reconfigurations in the future, with implications for sea level rise.
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