Ice rafts traveling farther and faster across the Arctic Ocean

SAN FRANCISCO — Climate change could turn the Arctic Ocean into an ice autobahn. Sea ice, much of it chunks of floating ice, is becoming younger and thinner as old ice melts. That new ice travels farther and faster than older ice, carrying dirt, organisms and pollution along for the ride, new research shows.

Tracking the movements of Arctic ice over several years, researchers noticed that ever larger areas of ice now make the trek from one side of the ocean to the other. That movement means that the far-flung reaches of the Arctic are becoming more connected, Robert Newton said December 16 at the American Geophysical Union’s fall meeting. That’s a problem, as migrating ice will boost the risk of widespread environmental disaster from events such as oil spills, said Newton, an oceanographer at Columbia University’s Lamont-Doherty Earth Observatory in Palisades, N.Y.

“You might imagine that the ice is this pristine environment, but that’s not true,” he said. “The ice in the Arctic is surprisingly polluted, and when the ice travels from one part of the Arctic to the other, it carries all that material with it.”

Winds sweep airborne pollution north from lower latitudes, where it settles into the ocean and onto sea ice. Industries along the Arctic coastline, such as gold mining, oil extraction and copper refining, can also pollute the region’s waters. As new ice forms in the autumn and winter, that pollution, along with nearby sediment, gets trapped inside the ice. When ice melts during spring and summer, the ice drops its payload back into the ocean.

Between formation and melt, the ice can get pushed across the Arctic by winds and ocean currents. Young, thin ice is more likely to be prodded along by these forces. As sea ice cover shrinks (SN Online: 8/3/15), Newton and colleagues wondered what the impact would be on these ice rafts and the material they transport. Less ice means less capacity to carry a large load of pollutants and debris, but a less crowded Arctic lets ice travel farther and faster.

The researchers assembled satellite snapshots of the Arctic and used sophisticated computer software that can recognize the edges of sea ice. Paired with GPS-tracked buoys and atmospheric data, the team followed the movements of ice from formation to disintegration.

Most Arctic ice does not go far. About 60 percent of ice travels less than 100 kilometers from its birthplace, the team found. The remaining ice, equivalent to tens of thousands of square kilometers, can travel hundreds or even thousands of kilometers. If the past is any indication, that amount is still rising. Newton estimates that an approximately 8 to 10 percent larger area of ice now travels a significant distance over its lifetime than did around 15 years ago. That ice is moving faster, too: Ice now travels from Russia to Canada in four to five years or less, down from six to seven years in 2000.

The new work may underestimate the amount of wandering ice and the threat it poses, said sea ice geophysicist Andy Mahoney of the University of Alaska Fairbanks. Fresh, fast-moving ice forms during October and November, but satellites struggle to capture that young ice. An oil spill during the summer could become trapped in this autumn ice and quickly move from one country’s waters to another’s, Mahoney said, rapidly spreading the spill’s ecological impact.