Tropical Pacific to see the greatest increases, while relative sea level is likely to drop in some polar regions
By Summit Voice
FRISCO — Intensifying concerns about the potential for sea level rise to swamp low-lying Pacific island nations are justified, according to a new report in the Geophysical Research Letters journal. Western Australia, Oceania and the small atolls and islands in this region, including Hawaii, are at greatest risk, according to the new study from EU’s ice2sea program.
The results of the modeling mirror observational data that’s been collected by satellites in the past few decades, said David Vaughan, program coordinator for EU’s ice2sea program, which seeks to develop more accurate sea level rise predictions.
“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,” Vaughn said, explaining that some regions will actually see relative sea levels decline because of the way land and ice interact globally.
The report gives a nuanced view of sea level rise, including factors like thermal expansion and the contribution of the melting cryosphere, Vaughn explained. The study isn’t the last word, but part of the evolving science of forecasting sea level rise more accurately.
Identifying specific geographic areas that will see a higher-than-average surge in sea level will actually help planners and decision-makers on the ground, Vaughn said. The information will help regions focus resources where they’re needed most — finding the best location for infrastructure, bolstering coastal defenses or, in some cases, planning relocation.
A talk several weeks ago by NOAA’s acting coastal programs director Margaret Davidson described those collaborative planning efforts during a Breckenridge, Colorado conference several weeks ago, saying that “today’s flood is tomorrow’s high tide.”
The ice2sea research team included scientists from Italy’s University of Urbino and the UK’s University of Bristol. The study focused on three effects that lead to global mean sea-level rise being unequally distributed around the world.
One key factor is the continuing subsidence and emergence of land masses 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 the process is still ongoing.
The overall warming of the oceans will also change in the distribution of water across the globe by altering circulation patterns and currents. For example, scientists have documented a depletion of deep, cold water in the Southern Ocean around Antarctica, a reservoir that helps drive ocean currents worldwide — in effect, the globe’s coldest water is vanishing, which could weaken a major pump in global ocean circulation.
The new ice2sea paper also suggests that the loss of ice in Greenland and Antarctica will reduce the gravitational pull of those areas. Sea level will actually drop as the water sloshes away toward the equator.
“In the paper we are successful in defining the patterns, known as sea level fingerprints, which affect sea levels,” said University of Urbino Professor Giorgio Spada. “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,” Spada said, adding that, in Europe, sea level will 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,” Spada said.
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.
“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,” he said.