The thickness of Arctic sea ice "plummeted" last winter, thinning by as much as one-fifth in some regions, satellite data has revealed.
© unknownThe data proves that overall volume of sea ice is decreasing, say researchers
A study by UK researchers showed that the ice thickness had been fairly constant for the previous five winters.
The team from University College London added that the results provided the first definitive proof that the overall volume of Arctic ice was decreasing.
The findings have been published in the journal Geophysical Research Letters
"The ice thickness was fairly constant for the five winters before this, but it plummeted in the winter after the 2007 minimum," lead author Katharine Giles told BBC News.
Sea ice in the Arctic shrank to its smallest size on record in September 2007, when it extended across an area of just 4.13 million sq km (1.59 million sq miles), beating the previous record low of 5.32 million sq km, measured in 2005.
The team from the university's Centre for Polar Observation and Modelling - part of the UK's National Centre for Earth Observation - found that last winter the ice had thinned by an average of 10% (26cm/0.9ft) below the 2002-2008 winter average.
Dr Giles added that the data also showed the western Arctic experienced the greatest impact, where the ice thinned by up to 19% (49cm/1.6ft).