Rate of decline in the thickness of Arctic sea ice is faster than the earlier scientific estimates because satellite measurements have failed to take into account salty snow on the surface of the ice, a new study from the University of Calgary in Canada said on Tuesday.
A study led by Calgary’s Cryosphere Climate Research Group has concluded that the "long-held scientific estimates of Arctic sea ice thickness and the rate at which it’s declining have been off significantly."
According to Vishnu Nandan, the lead author of the study, Arctic Ocean could be ice-free much sooner than some scientific predictions which forecast it occurring between 2040 and 2050.
The researchers found that satellite estimates for the sea ice thickness of seasonal ice (one-year-old ice) have been overestimated by up to 25 per cent due to the saline properties of snow cover on top of the ice, affected the accuracy of satellite readings.
As such, that ice can likely be expected to melt earlier than projected, says the study published in the academic journal Geophysical Research Letters.
The study calls into question measurements provided over the past decade by the European Space Agency’s satellite, CryoSat-2, which has been the most prominent satellite measuring Arctic sea ice thickness.
“It has been assumed by the scientific community that CryoSat-2 can accurately measure the sea ice freeboard, which is the ice we can see above sea level,” says Nandan.
“But that ice is covered in snow and the snow is salty close to where the sea ice surface is. The problem is, microwave measurements from satellites don’t penetrate the salty snow very well, so the satellite is not measuring the proper sea ice freeboard and the satellite readings overestimate the thickness of the ice,” he said.
Previous study found that the thickness of ice has been declining at a rate of 17 per cent per decade since 1979. The new research however, says the rate of summer sea ice decline could be slightly faster.
To compensate for the inaccuracy of the satellite readings researchers devised a correction factor that takes into account the snow salinity. This involves a combination of microwave theory and over 10 years of snow property data in the Canadian Arctic.
The study said that the consequences of ice-free summers in the Arctic Ocean would be enormous.
“Such a transition would radically affect global weather patterns and dramatically increase the magnitude and frequency of storm events,” John Yackel, geography professor at the University of Calgary and co-researcher of the study said. “It would also dramatically alter the Arctic marine ecosystem, with the added sunlight affecting the Arctic Ocean food web and melting the very ice bed on which animals like polar bears hunt.”
Yackel added, “Our results suggest that snow salinity should be considered in all future estimates on the Arctic seasonal ice freeboard made from satellites.”
