The melting of the ice sheets led to a rise in sea level to 18 meters

An isolated lake in the north-west of Scotland. Sediments analyzed from the bottom of this low-lying lake tell us that it was once connected to the ocean. Photo: Professor Ian Shennan, Department of Geography, Durham University.

It is well known that climate-induced sea-level rise is a serious threat. A new study has found that previous ice loss events could cause sea levels to rise at a rate of about 3.6 meters per century, offering vital clues about what lies ahead if climate change does not abate.

A team of scientists, led by researchers from Durham University, used geological data from past sea levels to shed light on the ice sheets responsible for the rapid pulse of sea-level rise in Earth's recent past.

Geological data tells us that at the end of the last ice age about 14,600 years ago, sea level rose tenfold on the current indicator due to Meltwater Pulse 1A (MWP-1A); 500 years, 18 meters of sea-level rise event.

Until now, the scientific community has not been able to agree on which ice sheet is responsible for this rapid rise, with the massive Antarctic ice sheet being a likely suspect, but some evidence pointing to ice sheets in the Northern Hemisphere.

The new study uses detailed geological data on sea level and the most advanced modeling techniques to identify the sources of MWP-1A. Interestingly, most of the meltwater appears to have originated from the former North American and Eurasian ice sheets, with minimal contribution from Antarctica, reconciling previously disparate views.

In addition to flooding vast areas of low-lying land, this unprecedented discharge of freshwater into the ocean, comparable to the melting of an ice sheet twice the size of Greenland in just 500 years, will disrupt ocean circulation, with implications for the global climate. Knowing the source of meltwater will increase the accuracy of climate models that are used to reproduce the past and predict changes in the future.

The results are important for our understanding of the interactions between ice and the ocean and climate, which play an important role in shaping terrestrial weather patterns. The findings are particularly timely due to the rapid melting of the Greenland ice sheet, which contributes to rising sea levels and changes in global ocean circulation.

From the results obtained, the lead author of the study, Yucheng Lin, in the Department of Geography at Durham University, notes: "Even though they were identified more than 30 years ago, it was surprisingly difficult to determine which ice sheet was the main factor behind this dramatic sea-level rise.

"Previously, scientists tried to work out the source of sea level rise based on sea level data from the tropics, but most of these studies did not agree with the geological data on the change in ice cover.

Our study includes new information from lakes around the Scottish coast that have been isolated from the ocean due to land rise following the retreat of the British ice sheet, allowing us to confidently identify the sources of meltwater."

Co-author Dr. Pippa Whitehouse, in the Department of Geography at Durham University, said: "The technique we used allows us to really dig into the error bars on the data and explore what ice-melting scenarios are most likely.

"We found that most of the rapid sea-level rise was caused by the melting of the ice sheet in North America and Scandinavia, with a surprisingly small contribution from Antarctica.

"The next big question is to find out what caused the melting of the ice and what effect the massive influx of meltwater had on the ocean currents in the North Atlantic. This is very much in our view today - any disruption of the Gulf Stream, for example, due to the melting of the Greenland Ice Sheet, will have significant consequences for the UK climate."

Rising sea levels due to a warming climate pose a great risk to society, and improving our understanding of why and how quickly changes can occur will help us plan for the consequences.

The study is published in the journal Nature Communications.

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