Scientists say current concerns over a tipping point in the disappearance of Arctic sea ice may be misplaced.
Danish researchers analysed ancient pieces of driftwood in north Greenland which they say is an accurate way to measure the extent of ancient ice loss.
Writing in the journal Science, the team found evidence that ice levels were about 50% lower 5,000 years ago.
They say changes to wind systems can slow down the rate of melting.
They argue, therefore, that a tipping point under current scenarios is unlikely.
While modern observations by ship and by satellite give us a very accurate picture of the recent state of the ice, historic information is limited. The ice comes and goes without leaving a permanent record.
But a Danish team believes it has found an indirect method that gives a clear picture of the ice loss dating back 11,000 years.
Dr Svend Funder from the Natural History Museum of Denmark led several expeditions to inhospitable regions of Northern Greenland. On these frozen shores the Danish team noticed several pieces of ancient driftwood. They concluded that it could be an important method of unlocking the secrets of the ancient ice.
"Driftwood cannot float across the water, it has to be ferried across the ocean on ice, and this voyage takes several years, which means that driftwood is actually a signal of multi-year sea ice in the ocean and it is this ice that is at risk at the moment" said Dr Funder.
Carbon dating was used to determine the age of the wood. And figuring out its origins also yielded important information.
"It's so lovely that drift wood from Siberia is mainly larch and from North America is mainly spruce. So if we see there was more larch or spruce we can see that the wind system had changed and in some periods there was little spruce and in other periods there was lots," he said...
Read more:
http://www.bbc.co.uk/news/science-environment-14408930
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