Arctic Neighbors May Pollute Each Others' Waters

The movement of sea ice between Arctic countries is expected to significantly increase this century, raising the risk of more widely transporting pollutants like microplastics and oil, according to new research. 

The study, published in the journal Earth’s Future, predicts that by mid-century, the average time it takes for sea ice to travel from one region to another will decrease by more than half, and the amount of sea ice exchanged between Arctic countries such as Russia, Norway, Canada and the U.S. will more than triple.

Contaminants in frozen ice can travel much farther than those in open water moved by ocean currents. Historically, floating masses of Arctic sea ice have been able to survive for up to 10 years, building up layers during much of the year, lasting through each summer and not moving very far during any given year, until finally floating out into warmer southern waters. As the climate warms, however, that pattern has been changing.

While overall, sea ice is thinning and melting entirely across vast regions in the summer, the more open water means the area of new ice formed during winter is actually increasing. This is the case particularly along the Russian coastline. The trend will probably soon extend into the central Arctic Ocean. This thinner ice can move faster in the increasingly open waters of the Arctic, delivering the particles and pollutants it carries to waters of neighboring states.

“Ice moves faster, but as the climate warms, it doesn’t have as much time as before to travel before it melts,” said lead author Patricia DeRepentigny, a doctoral candidate at the University of Colorado, Boulder. “Because of that, we really see that it’s the regions that are directly downstream of each country’s waters that are going to be most affected.”

Russia’s exclusive economic zone and the central Arctic Ocean are two places the researchers expect more new ice to form. This would make them major “exporters” of ice to other regions in the Arctic. 

The researchers used a global climate model, together with the Sea Ice Tracking Utility, to track sea ice from where it would form to where it would ultimately melt during the 21st century. They considered two different emissions scenarios: the more extreme “business as usual” scenario, which predicts warming of 4 to 5 degrees Celsius by 2100, and a warming scenario limited to 2 degrees Celsius, inspired by the Paris Agreement. They then modeled how sea ice would behave in both these scenarios at the middle and the end of the century.

In three of these four situations, including both mid-century predictions, the movement of sea ice between Arctic countries increased. But in the high-emissions scenario at the end of the century, the researchers found countries could end up dealing more with their own ice and its contaminants than ice from their neighbors. In that case, the majority of sea ice that freezes during winter would melt each spring in the same region where it formed.

The study was coauthored by Alexandra Jahn of the University of Colorado Boulder, L. Bruno Tremblay of McGill University, Stephanie Pfirman of Arizona State University and Robert Newton of Columbia University’s Lamont-Doherty Earth Observatory.