Arctic heat waves cause exceptional Greenland melt, says new study
Influxes of warm air from lower latitudes may be causing highest melt rates
A new study by researchers from Denmark and Canada's York University says Arctic heat waves cause exceptional melts of the Greenland ice sheet, calling into question commonly-used climate models that may underestimate the impact of warm weather episodes.
The study published in Geophysical Research Letters looked at causes of ice melt during two exceptional melt episodes in 2012 from July 8-11 and July 27-28. These six days accounted for 14 per cent of the annual melt in 2012 and the highest daily melt rates ever observed in the Greenland ice sheet to date.
"That was about 28 cm per day of ice melting at the southern tip of the Greenland ice sheet," said William Colgan, co-author of the study from York University's Lassonde School of Engineering.
"This is a really remarkable observation of just how fast the Greenland ice sheet is melting."
Using new technology, the researchers were able to see the daily rate of ice melt, even when the melt rate was very large.
They say it wasn't energy from radiation such as solar radiation that was causing the most ice melt, as was previously assumed. It was non-radiant fluxes of warm air being pushed up against Greenland or into Baffin Bay from lower latitudes.
"That was kind of surprising," said Colgan.
Sign of things to come
As the climate warms, the exceptional periods observed in July 2012 in Greenland may become the rule, said Colgan.
"In a warming climate the equator is getting even more energy than it used to, so it wants to push even more energy North into the Arctic and south into the Antarctic," said Colgan.
The findings may have major implications for how scientists study climate change.
"Looking forward, we're saying that we've got to pay attention to these short period events, these sort of one-to-two-day heat waves that blast north and bring warm air to the ice sheet," said Colgan.
He added that if future weather models don't investigate these heat waves they may miss or underestimate the melt rate.
Implications for Nunavut
It is not only the Greenland ice sheet that will be affected as warm and often moist air moves from low latitudes to the poles.
"When those air masses or heat waves move North they flood right into Baffin Bay and they affect all of Nunavut and you can see evidence of enhanced sea ice melt as well as enhanced snow melt on land," said Colgan.
Jimmy Akavak, originally from Kimmirut, said he has noticed rapid melts on the land.
"I've seen the change where you can Ski-Doo no problem one day on the land and some ice and it does change in a matter of a few days, even a weekend," he said.
Akavak said he really noticed the fast rate of melting snow and ice in May about 10 years ago.
"People were out camping and fishing and they could barely get back over land because of the melt," he said.
He said in the past 10 to 15 years the melt rate has dramatically increased.
"Three weeks to a month earlier now than before — the ice is melting a lot quicker — you could almost see the ice melting in front of you."
Working on shifting Arctic ice
Colgan said it's not easy to maintain a weather station around the edge of the melting Greenland ice sheet, so the tools they use such as the PROMICE automatic weather station are designed to withstand the elements.
"They're super robust or sturdy so that they can withstand the harsh Arctic climate and get buried with snow and come out OK on the other hand," said Colgan
The weather stations are installed on the site and left to gather data for a year. They collect all their own power through solar panels and save that power through the polar night in large car batteries that are in an insulated box. They then come back online in the spring and transmit their data via satellite so that the researchers can see if there are any problems with the station before heading back to the field.
"When you go and put your instrumentation out one year and you come back the next year, the whole surface looks radically different," said Colgan.
"The ice sheet is changing so fast that the ground, or in this case the ice, is literally shifting under our feet and under our instruments' feet."