The melting of the Greenland ice sheet due to climate change is having an impact on ocean circulation and rising sea levels, according to new studies from university researchers across North America.

"It was well known that Greenland's ice was melting, it was well known that that melting was accelerating, and it was well known that extra melting was changing the salinity of the North Atlantic Ocean," said Tim Dixon, a Canadian professor in the department of geophysics at the University of South Florida, who recently co-authored a study published in Nature Communications

Dixon said that when ice melts, it deposits fresh water into the ocean that dilutes the salt in the North Atlantic.

"What was not known is what effect if any that would have on ocean circulation," he said.

Ocean circulation graphic

'In the extreme case of a breakdown in this global ocean circulation pattern, equatorial regions could become much hotter than they are today and polar regions could become much colder than they are today, and significant fractions of the globe might become unlivable,' said University of South Florida's Tim Dixon. (Tim Dixon)

Previous studies had suggested that the impact of the melting Greenland ice on North Atlantic circulation would be minimal, at least for the next 50 years, Dixon said, because the amount of fresh water going into the North Atlantic was thought to be too small to disrupt the ocean circulation.

"The accelerated melting of Greenland is adding so much fresh water to the North Atlantic that it's starting to affect the basic ocean structure in the Labrador Sea." 

But it's not just the Labrador sea that is affected.

"We think those changes are big enough that they're starting to affect the overall global circulation pattern of the ocean," Dixon said.

'Fractions of the globe might become unlivable'

Altering the circulation pattern of the ocean can have drastic long-term implications, Dixon said.  

"In the extreme case of a breakdown in this global ocean circulation pattern, equatorial regions could become much hotter than they are today and polar regions could become much colder than they are today, and significant fractions of the globe might become unlivable." 

River exiting from beneath the ice sheet near Kangerlussuaq

'The rate of mass loss that the ice sheet is now exhibiting post 2010, is somewhere in the neighbourhood of three times higher than the rate of mass loss prior to the 1980s,' said Colgan. (William Colgan)

These changes are some of the first alarming signals of the possible effects of climate change, Dixon said.

"This is the first hint that these effects are starting a bit faster than people had imagined and implying that we need to get our act together and do something about this," he said.

"Which means we have to stop putting so much CO2 into the atmosphere."

Ice melt changing earth's gravity field

William Colgan of York University in Toronto has also been studying the rate of the Greenland ice melt and its effects on the ocean. In a recent study, published in the journal Science, he looked at historical data and compared it to new information gathered from expeditions in 2012, 2013 and 2015.  

William Colgan

'Iqaluit will not be flooded out by rising sea level but to have the harbour in Iqaluit, which is already really shallow get shallower at 1 cm per year going forward that can also be a very damaging sequence of sea level change,' said York University’s William Colgan. (William Colgan)

"The ice sheet didn't really start to accelerate and lose a lot more mass until the year 2000," he said.

"The rate of mass loss that the ice sheet is now exhibiting, post 2010, is somewhere in the neighbourhood of three times higher than the rate of mass loss prior to the 1980s." 

Greenland is losing about 8,300 tonnes of ice per second each day —  ice that is melting on land and running into the water, as well as icebergs that are being discharged into Baffin Bay, said Colgan.

"That's a rapid, rapid mass loss that's occurring in Greenland right now and it's actually changing the Earth's gravity field so quickly that we can detect it with satellite." 

Colgan said that just like the moon pulls tides around the Earth with its gravity, by being relatively massive, Greenland pulls water towards it. As Greenland gets smaller, the ocean water flows farther away towards the equator, in what is called a gravitational far-field.

Implications for Nunavut

Icebreaker approaches bay

Colgan said the sea level has been decreasing in Frobisher Bay at around 1 centimetre per year, an effect that can be as damaging as sea level rise. (Sima Sahar Zerehi/CBC)

Colgan said this change will have implications for places close to Greenland like Nunavut.

"Actually close to Greenland, sea level rise is negative,or sea level is dropping, in part because the gravitational field is weakening so quickly that the water in the ocean is migrating to more gravitationally massive places on Earth."

Colgan said the sea level has been decreasing in Frobisher Bay at around one centimetre per year, an effect that can be as damaging as sea level rise.

"Iqaluit will not be flooded out by rising sea level but to have the harbour in Iqaluit, which is already really shallow, get shallower at one centimetre per year going forward, that can also be a very damaging sequence of sea level change," he said.

The melting of Greenland ice also produces more icebergs which are being discharged from the glaciers on land.

"There's actually more icebergs now being spat out into Baffin Bay and floating around as potential navigation hazards than there were 50 or even 10 years ago," said Colgan.