Public Release:  New projections of 'uneven' global sea-level rise

Reporting in the journal Geophysical Research Letters researchers have looked ahead to the year 2100 to show how ice loss will continue to add to rising sea levels

British Antarctic Survey

Sophisticated computer modelling has shown how sea-level rise over the coming century could affect some regions far more than others. The model shows that parts of the Pacific will see the highest rates of rise while some polar regions will actually experience falls in relative sea levels due to the ways sea, land and ice interact globally.

Reporting in the journal Geophysical Research Letters researchers have looked ahead to the year 2100 to show how ice loss will continue to add to rising sea levels. Scientists have known for some time that sea level rise around the globe will not be uniform, but in this study the team of ice2sea researchers show in great detail the global pattern of sea-level rise that would result from two scenarios of ice-loss from glaciers and ice sheets.

The team, from Italy's University of Urbino and the UK's University of Bristol, found that ice melt from glaciers, and the Greenland and Antarctic ice sheets, is likely to be of critical importance to regional sea-level change in the Equatorial Pacific Ocean where the sea level rise would be greater than the average increase across the globe. This will affect in particular, Western Australia, Oceania and the small atolls and islands in this region, including Hawaii.

The study focussed on three effects that lead to global mean sea-level rise being unequally distributed around the world. Firstly, land is subsiding and emerging due to a massive loss of ice at the end of the last ice age 10,000 years ago when billions of tons of ice covering parts of North America and Europe melted. This caused a major redistribution of mass on the Earth, but the crust responds to such changes so slowly that it is still deforming. Secondly, the warming of the oceans leads to a change in the distribution of water across the globe. Thirdly the sheer mass of water held in ice at the frozen continents like Antarctica and Greenland exerts a gravitational pull on the surrounding liquid water, pulling in enormous amounts of water and raising the sea-level close to those continents. As the ice melts its pull decreases and the water previously attracted rushes away to be redistributed around the globe.

Co-author Professor Giorgio Spada says, "In the paper we are successful in defining the patterns, known as sea level fingerprints, which affect sea levels.

"This is paramount for assessing the risk due to inundation in low-lying, densely populated areas. The most vulnerable areas are those where the effects combine to give the sea-level rise that is significantly higher than the global average."

He added that in Europe the sea level would rise but it would be slightly lower than the global average.

"We believe this is due to the effects of the melting polar ice relatively close to Europe - particularly Greenland's ice. This will tend to slow sea-level rise in Europe a little, but at the expense of higher sea-level rise elsewhere."

The team considered two scenarios in its modelling. One was the "most likely" or "mid-range" and the other closer to the upper limit of what could happen.

Professor Spada said, "The total rise in some areas of the equatorial oceans worst affected by the terrestrial ice melting could be 60cm if a mid-range sea-level rise is projected, and the warming of the oceans is also taken into account." David Vaughan, ice2sea programme coordinator, says, "In the last couple of years programmes like ice2sea have made great strides in predicting global average sea-level rise. The urgent job now is to understand how global the sea-level rise will be shared out around the world's coastlines. Only by doing this can we really help people understand the risks and prepare for the future."

Co-author Jonathan Bamber, of Bristol University, says, "This is the first study to examine the regional pattern of sea level changes using sophisticated model predictions of the wastage of glaciers and ice sheets over the next century."

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Notes for editors:

The paper "The gravitationally consistent sea-level fingerprint of future terrestrial ice loss" is published in Geophysical Research Letters online. Graphics and abstract available.

To request an interview with Professor Giorgio Spada please contact Anuska Pambiachi at the Urbino University Press Office, Italy.

Email: anuska.pambianchi@uniurb.it

To request an interview with Professor David Vaughan please contact the Paul B. Holland at the British Antarctic Survey Communications Office, Cambridge.

Tel: 01223 221226; Email: pbmho@bas.ac.uk

To request an interview with Professor Jonathan Bamber or Dr Ruud Hurkmans please contact Hannah Johnson at the Public Relations Office, Communications Division, University of Bristol.

Tel: (0117) 928 8896; Email: hannah.johnson@bristol.ac.uk

Ice2sea brings together the EU's scientific and operational expertise from 24 leading institutions across Europe and beyond. Improved projections of the contribution of ice to sea-level rise produced by this major European-funded programme will inform the fifth IPCC report (due in 2013). In 2007, the fourth Intergovernmental Panel on Climate Change (IPCC) report highlighted ice-sheets as the most significant remaining uncertainty in projections of sea-level rise.

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