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Nature / New study says isles were covered by own ice sheet thousands of years ago

An erratic boulder being examined at Muckle Roe that was deposited by retreating glaciers around 17,000 years ago.

RESEARCHERS say that a large ice sheet covered Shetland and its surrounding seafloor tens of thousands of years ago.

The study, which was led by the University of Stirling, said there was “clear and unequivocal” evidence that Shetland hosted its own ice sheet.

The research found that the sheet covered more than 50,000 square kilometres and was in existence between 30,000 and 19,000 years ago before reducing in size.

Scientists say that a smaller ice cap remained in Shetland for the next 3,000 years, melting completely 15,000 years ago.

Dr Tom Bradwell, of the Faculty of Natural Sciences at Stirling, said: “Our study has – for the first time – used onshore and offshore dating techniques, seabed mapping, and sediment analysis to reconstruct the complete deglaciation history of Shetland and the surrounding continental shelf.

“Our findings are clear and unequivocal: Shetland and the surrounding sea floor – once dry land – hosted an ice sheet between around 30,000 to 19,000 years ago. It was glaciologically independent from the Scottish and Fennoscandian ice sheets – but, at times, was connected to both.

“The marine portion of the ice sheet reduced in size dramatically between 19,000 and 18,000 years ago – leaving just a small, independent ice cap centred on mainland Shetland by 17,000 years ago. By 16,000 to 15,000 years ago, all of the remaining glaciers on Shetland had melted.”

The university said that for years scientists have been unsure as to whether Shetland had its own independent ice cap or if it was “overrun” by a larger sheet.

The new research – part of the wider BRITICE-CHRONO project, led by Professor Chris Clark at the University of Sheffield – was carried out by a 17-strong team of researchers from several UK institutions.

Speaking about how the findings fit in with more topical talk on climate change, Bradwell said: “Today, the longer-term forecasts of global sea-level rise are hampered by modelling uncertainties, with current estimates widely ranging depending on the behaviour of marine ice sheets and their fronting ice shelves.

“Our reconstructed record shows a massive abrupt reduction, or collapse, in Shetland’s marine ice sheet over the northern North Sea around 19,000 to 18,000 years ago – more than halving in volume – probably triggered by an instability process as sea levels rose.

“These results have strong parallels with recent findings from the Intergovernmental Panel on Climate Change, which highlighted the increased likelihood of near-future ‘large-scale singular events’ – such as Greenland ice-shelf collapse and West Antarctica marine ice sheet instability – in response to global warming above 1.5°C.”