Melting ice could lead to 7-meter sea rise, warns study

Melting ice could lead to 7-meter sea rise, warns study

Melting ice could lead to 7-meter sea rise, warns study

In July 2012, a spate of warm weather caused almost the entire surface of the Greenland ice sheet to begin melting, an event with no precedent in the satellite record. The melting is not just increasing - it's accelerating.

Ice loss from Greenland is the single largest contributor to global sea-level rise, which is predicted to lead to inundation of low-lying islands and coastal cities around the world over the next several decades and centuries.

Today, these rates are "off the charts", said glaciologist Sarah Das, who is a co-author of the study, published this week in the journal Nature.

The team was then able to use modern, precise measurements of melt and correlate those measurements with the pattern seen in the ice cores, which allowed them to estimate what melt at lower elevations across the island would have looked like in each year recorded in the high-elevation cores.

The enormous sheet, which covers an area two and a half times that of the United Kingdom, is dumping more melted ice into the oceans than at any point during the past 400 years, according to a new study.

The year 2012, in particular, was a standout for ice melt. At higher elevations, however, the summer meltwater quickly refreezes from contact with the below-freezing snowpack sitting underneath.

The research also discovers that the estimate of melting at Greenland's surface has shot up in recent years and now is beyond the limits of what was contemplated organic changeability over the last few centuries.

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Most previous research has used satellite observations and computer modelling to calculate the rate of melting in Greenland. Instead of escaping the ice sheet, the short-lived meltwater forms icy bands that stack up layers of densely packed ice over time.

Analysis of ice core samples from sites 6,000ft (1,829m) above sea level has enabled the researchers to assess melting dating back 350 years.

The scientists combined the results from ice cores with satellite data and climate models to reconstruct melt-water runoff at lower elevations on the edge of the ice sheet that contributes to sea level rise.

"We have had a sense that there's been a great deal of melting in recent decades, but we previously had no basis for comparison with melt rates going further back in time", Osman said.

Das and her colleagues at Rowan University and elsewhere reached that conclusion by examining three ice cores from central west Greenland, and one from an ice cap off the coast, that contain a history of melt events spanning the past 350 years. Now, even a very small temperature change in the region can cause huge spikes in ice sheet melting, according to the study. The satellites used to study ice sheet melting around the world haven't been around long enough to capture a complete picture of the melting process.

"To be able to answer what might happen to Greenland next, we need to understand how Greenland has already responded to climate change", he said.

The U.S. Department of Defense, the Netherlands Organization for Scientific Research, the Netherlands Earth System Science Center, and the Belgian National Fund for Scientific Research also provided institutional support to the effort.

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