Study: Greenland, Antarctica shed nearly 5 trillion tons of ice over 20 years

Melting faster than it's growing. For two decades, uncertainty over whether Antarctica was gaining mass or losing it from melting ice has made it difficult for scientists to predict the level of sea-level rise to be expected from global warming. The data showed, in the view of some scientists, that ice loss in the Arctic was being balanced by a gain in the Antarctic. Now a study published in the Nov. 30 issue of Science shows conclusively from satellite data that East Antarctica is, in fact, gaining ice, but the loss from western Antarctica and the Antarctic peninsula is twice as great as that gain.

In Greenland, the study concludes, ice is now melting at five times the rate it was in the 1990s.

Together with ice lost in Greenland, the melting in Antarctica has, the scientists say, raised sea levels worldwide by 11 mm in those 20 years, several times as much as previous measurements have shown. Combined loss: nearly 5 trillion metric tons of ice.

"The estimates are the most reliable to date, and end 20 years of uncertainty of ice mass changes in Antarctica and Greenland," said study leader, Andrew Shepherd, of Leeds University. "There have been 30 different estimates of the sea level rise contribution of Greenland and Antarctica, ranging from an annual 2mm rise to a 0.4mm fall.

"We can state definitively that both Greenland and Antarctica are losing mass, and as [the] temperature goes up we are going to lose more ice."

The Guardian has an interactive map for both here and here.

The scientists point out that the study does not resolve all the issues needed to predict how great sea-level rise will be because the interactions between warming air, warming seas, glaciers and the two giant ice sheets of Greenland and Antarctica as hugely complex. Ian Joughlin, a member of the study team from the University of Washington, Seattle, said: "In Greenland, we are seeing really dramatic losses in ice, but it is still uncertain if it will slow, stay the same or accelerate further."

The sea-level rise of about a half-inch may seem small, but:

Study lead author Andrew Shepherd of the University of Leeds in England, said their results provide a message for negotiators in Doha, Qatar, who are working on an international agreement to fight global warming: 'It's very clear now that Greenland is a problem.' [...]

That seemingly tiny extra bit probably worsened the flooding from an already devastating Superstorm Sandy last month, said NASA ice scientist Erik Ivins, another co-author of the study. He said the extra weight gives each wave a little more energy.

'The more energy there is in a wave, the further the water can get inland,' Ivins said.

Part of that rise in sea level comes from the expansion of water because the ocean itself is warming. That warming contributes to the intensity of storms while the higher sea levels means higher storm surges, which, as seen in Hurricane Sandy can be immensely damaging.

In another study just published Nature Geosciences magazine, Alejandro Orsi, associate professor of oceanography, and his colleagues from the University of Gothenburg in Sweden, researched steady warm water flows under the Antarctic ice shelves that extend from land into the surrounding Southern Ocean. The study added to concerns that warmer water may be contributing more to glacial loss on the continent than is warming air.

Perhaps, after having poured a billion or two dollars into denialist propaganda and buying puppets in Congress over the years, the Koch brothers and their ilk will soon be telling us no problem, we can grow wheat and corn in Antarctica to replace the losses in the world's existing agricultural belts.