Study reveals how Arctic Ocean drives ice melt

By Yuri Bult-Ito
Public Information Officer for UAF’s International Arctic Research Center

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Photo by Adrienne Tivy A curious young bear circles the research ship CCGS Louis S. St-Laurent in Franklin Strait along the Northwest Passage above the Arctic Circle. Under the bear are pieces of first-year sea ice in the process of melting.

Unprecedented ice melt in the Arctic Ocean is not caused by warming air alone, according to a recent study that emerged from a workshop at the University of Alaska Fairbanks.

Sea ice in the Arctic has continued to get thinner and smaller and to move faster during the past two decades.

Examining a collection of observational data obtained for more than two decades, a group of more than two dozen international researchers gathered at the March 2013 workshop to tackle the question of whether the increasing warmth of the Arctic Ocean itself is melting its own cover of ice.

The results were published in December in the Bulletin of the American Meteorological Society.

Researchers investigated how the effects of ocean currents, salinity, wind and ice interact with one another to accelerate sea ice melting. They showed that small changes in ways the ocean transports heat to the ice cover could have a substantial impact on future changes in Arctic ice cover.

“Sea ice loss has implications for governance, economics, security and global weather, so it is critical to understand how ocean, ice and air interact,” said Igor Polyakov of the UAF International Arctic Research Center, who was one of the lead authors of the study.

The Atlantic and Pacific Oceans are heating up and warmer currents are flowing into the Arctic Ocean. The heat from these currents would melt the Arctic sea ice instantly, Polyakov said, but so far it hasn’t happened because the warm currents don’t come into direct contact with the ice.

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Photo by Yuri Bult-Ito International Arctic Research Center researcher Igor Polyakov sits in front of monitors displaying observational data from the Arctic Ocean.

“The reason is these currents are saltier, therefore heavier, so they sink deeper into the ocean. Colder, fresher surface water partly shields the ice on the surface from warm water below,” he said.

Wind and faster-moving ice floes stir the ocean below, causing cold surface water and warm waters below to mix. As they are mixed, warmer water is brought to the surface and melts the ice cover from beneath it.

As this process continues, more sea ice melts.

The heat from the sun not only directly melts the sea ice but also heats up the water between ice floes, which is darker than ice and absorbs more heat. The heat from the sun also penetrates the thin areas of the ice, causing them to break from bigger, solid masses of ice. These smaller ice floes move freely.

Fresh water rushing from the large Siberian and North American rivers add more warm water to the ocean and accelerate ice melt, according to the paper.

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Photos by Jenny Hutchings (left) and Alice Orlich (right) These photos were taken at the same site in the Arctic Ocean (78 degrees N, 150 degrees W) during separate research expeditions aboard the Canadian Coast Guard Ship Louis S. St-Laurent in 2006 (left) and 2012 (right).

The Arctic is warming faster than any other region on the planet.

“Sea ice melt in the Arctic is one of the most visible indicators of global climate change,” said Peter Winsor of the UAF Institute of Marine Science, who contributed to the study.

The study presents the most comprehensive summary so far of the current understanding of how heat reaches the ice base from the original sources, such as currents from different oceans and river discharge. The study gives key directions for creating more realistic future projections of the warmer and more dynamic “new Arctic.”

“Physical mechanisms within the Arctic Ocean impact biological, chemical, geological and physical processes and occur across sovereign state boundaries,” noted Polyakov. “So it is really important that we make multidisciplinary, multiagency and multinational efforts to reduce uncertainties in the projections of the future Arctic.”

The Chapman Chair Untersteiner Workshop was hosted by the UAF College of Natural Science and Mathematics and the International Arctic Research Center at UAF.

ON THE WEB: The paper, entitled “Toward quantifying the increasing role of oceanic heat in sea ice loss in the New Arctic,” was published in the Bulletin of the American Meteorological Society.

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