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Arctic to green as Antarctic sea ice grows

Antarctic seaice

Sea ice around Antarctica is growing, while the Arctic is set to experience explosive greening due to global warming, researchers say (Source: Richard Bintanja)

Polar ice In the coming decades, global warming will cause grass, shrubs and trees to thrive in Arctic soil stripped of ice and permafrost, while sea ice around Antarctica will grow, according to new research published today.

Wooded areas in the Arctic could increase by as much as 52 per cent by the 2050s as the so-called tree line - the maximum latitude at which trees can grow - shifts hundreds of kilometres north, according to computer simulations published in the journal Nature Climate Change.

"Such widespread redistribution of Arctic vegetation would have impacts that reverberate through the global ecosystem," says Dr Richard Pearson of the American Museum of Natural History's Center for Biodiversity and Conservation.

The Arctic has become one of the world's 'hotspots' for global warming. Over the past quarter-century, temperatures there have been rising roughly twice as fast as in the rest of the world.

"These impacts would extend far beyond the Arctic region," says Pearson.

"For example, some species of birds seasonally migrate from lower latitudes and rely on finding particular polar habitats, such as open space for ground-nesting."

In a separate study, published today in the journal Nature Geoscience, Dutch scientists report that iceshelves in Antarctica - another part of the climate equation - have in fact been growing thanks to global warming.

Meltwater that runs off the Antarctic mainland provides a cold, protective "cap" for iceshelves because it comes from freshwater, which is not as dense as seawater, the team from the Royal Netherlands Meteorological Institute say.

Iceshelves are the floating blankets of ice that extend from the coast. They are fed by glaciers that move ice down from the icesheet and towards the sea.

The freshwater acts as a cold coating for the underside of the iceshelf, cocooning it from warmer seas, according to the new study.

This would explain an apparent anomaly: why sea ice around Antarctica has been growing, reaching the greatest-ever recorded extent in 2010, it suggests.

Other scientists, asked to comment on the work, concurred that the phenomenon, if confirmed, was one of several unexpected impacts from global warming, a hugely complex interplay of land, sea and air.

"This is a major, new piece of work with wide implications for assessing Antarctica's ice mass in the coming decades," says palaeo-climatologist Dr Valerie Masson-Delmotte of France's Laboratory for Climate and Environmental Science (LCSE).

She points to a worrying rise in sea levels in 2011 and 2012, due partly to expansion of the ocean through warming and through glacier runoff, coming from mountains and also from Greenland and Antarctica, the two biggest sources of land ice on the planet.

Tags: climate-change