Icecaps around the North and South Poles are melting faster and in a more widespread manner than expected, raising sea levels and fuelling climate change, a major scientific survey showed Wednesday.
The International Polar Year (IPY) survey found that warming in the Antarctic is "much more widespread than was thought," while Arctic sea ice is diminishing and the melting of Greenland's ice cover is accelerating.
Rising sea levels and changes in ocean temperatures triggered by the melting ice also heralded shifts in weather patterns worldwide and potentially more coastal storm surges, scientists said.
"We're beginning to get hints of change in ocean circulation, that'll have a dramatic impact on the global climate system," IPY director David Carlson told journalists.
The frozen and often inaccessible polar regions have long been regarded as some of the most sensitive barometers of environmental change and global warming because of their influence on the world's oceans and atmosphere.
Preliminary findings from the two year survey by thousands of scientists revealed new evidence that the ocean around the Antarctic has warmed more rapidly than the global average, the World Meteorological Organisation and the International Council for Science said in a statement.
Meanwhile, shifts in temperature patterns deep underwater indicated that the continent's land ice sheet is melting faster than reckoned.
"These changes are signs that global warming is affecting the Antarctic in ways not previously suspected," the statement added.
"These assessments continue to be refined, but it now appears that both the Greenland and the Antarctic ice sheets are losing mass and thus raising sea level, and that the rate of ice loss from Greenland is growing."
Shrinking sea ice was expected around Antarctica, while Arctic sea ice decreased to its lowest level since satellite records began.
Special IPY expeditions in the Arctic in 2007 and 2008 also found an "unprecedented rate" of floating drift ice.
But the focus was on the erosion of land-based ice sheets of Greenland and the Antarctic, which hold the bulk of the world's freshwater reserves and can generate sea level changes of global scale as they melt.
"That was an urgent question three years ago and I think today it's now a more urgent question," Carlson said.
When the survey began in 2007, Greeenland and Antarctica's land areas were viewed as largely stable despite some worrying signs of fringe melting.
The joint statement concluded: "The message of IPY is loud and clear: what happens in the polar regions affects the rest of the world and concerns us all."
The survey also revealed that the melting has the potential to feed more global warming in turn as the permafrost melts faster.
Permafrost, the expanse of continuously frozen soil in polar land areas, was found to have larger pools of carbon than expected and the melting could unleash more greenhouse gases into the atmosphere.
The scientists also found that global warming caused substantial changes that were tantamount to a greening of the Arctic landscape.
Vegetation and soil were changing in the region, with shrubbery taking over grassland and tree growth shifting according to changing snowfall, while insect infestation increased and species move from lower latitudes into polar regions.
Those shifts also disrupted native animals, hunting and local livelihoods, while building was taking place in previously uninhabited areas, the scientists found.
The survey around both poles was the first of its kind for half a century, revisiting areas that have not been seen since the 1950s and mobilising 10,000 scientists around the world.
AFP: Climate change: Atlantic shift has global impact
Wed Feb 25, 2:09 pm ET
Big changes in the circulation of the Atlantic Ocean probably have an impact around the globe, according to a study published Wednesday that touches on a key aspect of climate change.
Scientists delved into dramatic swings in climate that are believed to have occurred during the last Ice Age, about 110,000 to 10,000 years ago.
Until now, the evidence for these swings has come only from the northern hemisphere, leaving a knowledge gap about what happened to the climate in the southern part of the globe.
The paper, appearing in the British-based journal Nature, supplies at least part of the answer: when temperatures plunged in the North Atlantic, they soared in the South Atlantic, and vice-versa.
The evidence, culled from a sediment core drilled from the seafloor in the South Atlantic, supports a theory known as the "bipolar seesaw".
Under this hypothesis, when circulation in the Atlantic is badly disrupted, there is a major knock-on, but opposite, effect in the two hemispheres.
In the Atlantic, the Gulf Stream ferries warm water at the surface from the tropics to the northeast.
Thanks to this, Western Europe has a relatively balmy climate, even though it is in the same latitude as the northeastern United States and Labrador, where winters are harsh.
The warm water cools as it heads north, which causes it to sink. The cold returns southward again by deep ocean currents, back to the tropics, where it warms again and so-on.
The new study provides the first concrete evidence of an immediate "seesaw" connection between the North and South Atlantic, say the authors, led by Stephen Barker of Cardiff University in Wales.
What caused the swings during the last glacial age are not known for sure. They were probably fuelled by natural shifts in Earth's orbit and axis, which can have big consequences in the amount of heat we get from the Sun.
But comprehending the seesaw mechanism also has a bearing on understanding climate change today, which is inflicted by manmade greenhouse-gases, the authors say.
One theory is that a spurt of global warming could swiftly melt Arctic ice, causing a rush of cold water into the North Atlantic that would slow the Gulf Stream "conveyor belt" and plunge Western Europe into a deep chill, even a mini Ice Age.
The evidence for this is sketchy or debatable, but the scenario is taken seriously by many climate scientists.
One of the study's co-authors, Ian Hall, a scientist at Cardiff University, said a big shift of Atlantic circulation is unlikely to occur in any near future.
Even so, "our results suggest that if such an extreme scenario did occur, its effects could be felt globally within years to decades."