Melting ice sheets caused sea levels to rise up to 18 metres

an iceberg

Research led by our geography department has found that previous ice loss events caused sea-levels to rise around 3.6 metres per century, offering vital clues as to what lies ahead should climate change continue.

Research postgraduate Yucheng Lin worked with Dr Pippa Whitehouse, Dr Sarah Woodroffe and Prof. Ian Shennan, using geological records of past sea levels, to determine which ice sheets were responsible for a rapid sea-level rise in Earth’s recent past.

Geological records tell us that, at the end of the last ice age around 14,600 years ago, sea levels rose at ten times the current rate due to Meltwater Pulse 1A (MWP-1A); a 500 year, ~18 metre sea-level rise event.

Twice the size of Greenland

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

The new study uses detailed geological sea-level data and state-of-the-art modelling techniques to reveal 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, restoring formerly disparate views.

In addition to flooding vast areas of low-lying land, this unparalleled discharge of freshwater into the ocean – comparable to melting an ice sheet twice the size of Greenland in only 500 years – will have disrupted ocean circulation, with knock-on effects for global climate.

Improving climate change models

The results are important for our understanding of ice-ocean-climate interactions which play a significant role in shaping terrestrial weather patterns. The findings are particularly timely with the Greenland ice sheet rapidly melting, contributing to a rise in sea levels and changes to global ocean circulation.

The next big question is to work out what triggered the ice melt, and what impact the massive influx of meltwater had on ocean currents in the North Atlantic. This is very much on our minds today – any disruption to the Gulf Stream, for example due to melting of the Greenland Ice Sheet, will have significant consequences for the UK climate.

It is well known that climate-induced sea level rise is a major threat and, knowing the source of former large-scale meltwater events will improve the accuracy of climate models that are used to replicate the past and predict changes in the future.

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