Sea ice in the Arctic was at record lows for October as unusually warm waters slowed the recovery of the ice, Danish researchers said on Wednesday.
Diminishing sea ice comes as a reminder about how the Arctic is hit particularly hard by global warming.
Since the 1990s, warming has been twice as fast in the Arctic compared to the rest of the world, as a phenomenon dubbed “Arctic amplification” causes air, ice and water to interact in a reinforcing manner.
“The October Arctic sea ice extent is going to be the lowest on record and the sea ice growth rate is slower than normal,” said Rasmus Tonboe, a scientist at the Danish Meteorological Institute (DMI), noting the record was unequalled for at least 40 years.
According to preliminary satellite data used by the institute, sea ice surface area was at 6.5 million square kilometres (2.5 million square miles) on October 27.
Every year, some of the ice formed in the Arctic waters melts in the summer.
It usually reaches a low point of about five million square kilometres (1.9 million square miles), but then reforms to cover about 15 million square kilometres (5.7 million square miles) in winter.
Warmer temperatures are now reducing both the summer and winter extent of the ice.
Satellite data has been collected to monitor the ice precisely since 1979 and the trend towards a reduction is clear.
For the month of October, measurements show an 8.2 percent downward trend in ice over the last 10 years.
Warmer than normal
Already in September, researchers noted the second-lowest extent of sea ice recorded in the Arctic, though not quite hitting the low levels recorded in 2012.
But warmer-than-normal seawater slowed the formation of new ice in October.
Water temperatures in the eastern part of the Arctic, north of Siberia, was 2 degrees Celsius (35.6 degrees Fahrenheit) to 4C (39.2F) warmer than normal, and in Baffin Bay, it was 1-2C warmer, DMI said in a statement.
The institute said this was following a trend observed in recent years, which was described as a “vicious spiral”.
“It’s a trend we’ve been seeing the past years with a longer open-water season making the sun warm the sea for a longer time, resulting in shorter winters so the ice doesn’t grow as thick as it used to,” Tonboe said.
Since the melting ice is already in the ocean it does not directly contribute to the rise in sea levels.
But as the ice disappears sunlight “gets absorbed in the ocean, helping to further warm the Earth”, said Claire Parkinson, a climate scientist at NASA.