UNIVERSITY OF ALASKA FAIRBANKS
IMAGE: WATER FROM CANADAS MACKENZIE RIVER COMES INTO THE BLUE ARCTIC OCEAN IN JULY 2012
A new study shows that increased heat from Arctic rivers melts sea ice in the Arctic Ocean and warms the atmosphere.
The study, published this week in Science Advances, was led by the Japanese Agency for Marine Earth Research and Technology, with authors in the US, United Arab Emirates, Finland, and Canada.
According to the study, large arctic rivers contribute significantly more heat to the Arctic Ocean than they did in 1980. River heat is responsible for up to 10% of the total sea ice loss that occurred in the Arctic shelf region from 1980 to 2015. This melt is equivalent to about 120,000 square miles of 1 meter thick ice.
"If Alaska were covered by 1 meter thick ice, 20% of Alaska would have disappeared," said Igor Polyakov, co-author and oceanographer at the University of Alaska Fairbanks International Arctic Research Center and the Finnish Meteorological Institute.
Rivers have the greatest impact during the spring outbreak. The warming water flows into the ice-covered Arctic Ocean and spreads under the ice, causing it to disintegrate. As soon as the sea ice melts, the warm water warms the atmosphere.
Research found that much more river heat energy is released into the atmosphere than ice melts or heats the ocean. Because air is mobile, river heat can affect areas of the Arctic far removed from river deltas.
The impact was most pronounced in the Siberian Arctic, where several large rivers flow into the relatively flat shelf region that extends nearly 1,000 miles offshore. Canada's Mackenzie River is the only river large enough to be a significant contributor to sea ice melt near Alaska. However, the state's smaller rivers are also a source of heat.
Polyakov expects that rising global air temperatures will continue to warm Arctic rivers in the future. As rivers warm, more heat flows into the Arctic Ocean, more sea ice melts and accelerates the warming of the Arctic.
Rivers are just one of many sources of heat that are now warming the Arctic Ocean. The entire arctic system is in an extremely anomalous state as global air temperatures rise and warm Atlantic and Pacific waters infiltrate the region and the sea ice crumbles even in mid-winter. All of these components work together to create positive feedback loops that accelerate warming in the Arctic.
"It's very alarming because all of these changes are accelerating," said Polyakov. "The rapid changes over the past ten years are just incredible."
The authors of the paper include Hotaek Park, Eiji Watanabe, Youngwook Kim, Igor Polyakov, Kazuhiro Oshima, Xiangdong Zhang, John S. Kimball, and Daqing Yang.