Increase in fresh water in Arctic Ocean could affect global climate systems

New study shows increased precipitation and ice melt caused by climate change have left Arctic waters less salty, and repercussions will be felt much farther south

There is more fresh water in the Arctic Ocean and climate change is the reason, according to a new study.

Alexandra Jahn, the lead author of the study and assistant professor at the University of Colorado Boulder, said the ocean is already bearing the effects of climate change, with more fresh water stored there — and, within the next two decades, this additional water could drain into more southern oceans, affecting currents.

“It’s really sobering to see the system changing so much,” she said.

The higher volume of fresh water is diluting the Arctic Ocean, making it less salty, which is expected to continue with each passing decade as the climate warms.

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That the Arctic is a bellwether for climate change has become widely accepted — melting sea ice is a common example of this, but there are others. Since the late 1990s, for instance, there’s been 10 per cent more fresh water in the Arctic Ocean than before, totalling 10,000 cubic kilometres. If spread out evenly across the entire Arctic Ocean, this would have a depth of about 0.7 metres. 

The Arctic Ocean is made up of more fresh water than other oceans already, Jahn said, as a result of runoff, primarily from rivers on the large landmass that surrounds it and melting sea ice, which acts as a freshwater cache.

Previous research has delved into temporary fluctuations in fresh water in the Arctic Ocean due to its natural cycle, Jahn said. Her research, published in Geophysical Research Letters, takes the issue a step further, suggesting human-caused climate change will account for long-term changes in the ocean. 

“The question was, is this just a natural cycle, or is this already climate change?” she said. “We knew we were seeing [the impacts of climate change] in the sea ice, but, in the ocean, it wasn’t clear when we would see that. In this study we clearly found that this increase is already driven by climate change.”

The global repercussions of an Arctic Ocean with more freshwater 

The Arctic Ocean has veins on both sides of Greenland that flow into the North Atlantic. 

Because the ocean will see more fresh water due to increased precipitation and runoff and melting sea ice, the Nares Strait, which runs between Ellesmere Island and Greenland, is projected to have more fresh water, too, Jahn said. Other straits emptying out of the Arctic Ocean to the south and east of Greenland are projected to be affected afterward, she added, though scientists don’t know exactly why there would be a delay.

“A lot of these changes are emerging by 2040,” Jahn said, adding that the changes will be at a rate that couldn’t possibly have occurred if not for climate change. 

More fresh water making its way through the Arctic Ocean’s gateways, like Nares Strait, could have global repercussions, Jahn said, noting it could affect currents and, thereby, climate systems the world over. 

“Everything is connected,” she said. “As that water exits the Arctic, that fresher water will reach the North Atlantic.” There, the mix of cold Arctic water and warmer water from the south play an important role in global ocean currents, she said.

This, Jahn continued, affects the climate, not only in the Arctic, but in northern Europe, where there could eventually be longer heat waves in the summertime.

Study highlights role greenhouse gas emissions will play in Arctic Ocean change 

Jahn’s team used a climate model to determine when greenhouse gas emissions started to affect how much fresh water there is in the Arctic Ocean. 

The researchers used pre-industrial greenhouse gas emissions levels in the years leading up to 1850, and then increasing levels after that, up until 2005. From 2006 on, they looked at a limited increase of emissions that would result in a climate that’s 2 C warmer (the limit suggested by the Intergovernmental Panel on Climate Change), as well as the business as usual scenario of emissions that warms the planet by 4 C.

The team then looked at how freshwater levels fared under the climate model before the pre-industrial era and in the later years as emissions levels increased. It was in those later years that the models showed fluctuation and increases in freshwater levels in the Arctic that hadn’t occurred previously.

Since the only difference between these pre- and post-industrial scenarios was the greenhouse gas levels, they concluded this shift in freshwater levels in the Arctic Ocean are the result of climate change, rather than a natural cycle. And they determined that climate change is already impacting how much fresh water is in the ocean.

“From those simulations, we know that this departure into a different regime is forced by climate change, rather than a natural cycle,” she said. 

Limiting emissions to keep global warming to the recommended 2 C versus the current trajectory of 4 C has major implications for fresh water in the Arctic Ocean, Jahn said, even though it can’t prevent or reverse the changes that are already occurring.

“At the end of the century, there’s actually a big difference between the best and worst case scenario that we looked at, with the changes [being] much, much bigger, as one would expect, under high-emission scenarios than the lower-emission scenario,” she said.

By 2100, she added, we will not return to 20th century levels of Arctic Ocean salinity even under the reduction targets outlined by the Intergovernmental Panel on Climate Change. 

Changes in water around Victoria Island prompt one Elder to call for more research

Jimmy Haniliak, an Elder from Cambridge Bay, Nunavut, has a cabin near Victoria Island’s shore on the Arctic Ocean. He said the fish he’s caught this year have been wildly different than previous decades.

“Every summer I’ve always set my net for Arctic char, and this year I’ve been catching white fish mostly,” he said, adding that for the last 25 years he’s tended to catch “nothing but char.”

“I was quite surprised. I never ever catch white fish. I’ve wondered, what’s going on with our climate here? ”

Haniliak said the water levels of lakes on Victoria Island have been dropping — upward of 1.2 metres — and possibly draining into the ocean. When his father, a commercial fisherman, was alive, they would boat down rivers without any problems.

“We can’t now. It’s gone [down] quite a bit.”

Lower water levels and a white fish-only harvest may not be directly related to more fresh water in the Arctic — but they could be. That’s why Haniliak wants to see more research completed in the area, noting that this summer has been a write-off, with no researchers visiting due to travel restrictions around the COVID-19 pandemic.

“Something’s going on here,” Haniliak said. “We need to have some studies. Without doing studies, then we really don’t know.”

Susanna Fuller, vice-president of operations and projects at the charity Oceans North, said there needs to be more research into the social and cultural impacts of climate change, including the fallout of more fresh water in the Arctic Ocean.

Country food, for instance, could become more scarce as the region becomes more ice-free, Fuller said.

And less ice means Arctic waters will become more navigable, allowing for increased shipping.

“It’s kind of equivalent to having an urban backyard and suddenly a transport truck drives up in your backyard. I think there will be all sorts of activity that increases, as traditional activities decrease.”

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