Researchers Study How Warm, Subsurface Water Affects Accelerated Arctic Sea-ice Melt

Sep 18, 2015

A near-record year for Arctic Ocean sea-ice retreat – and researchers are on site to study why …


Scientists aboard the Arctic Research Vessel Sikuliaq say it appears sea ice in the far north has retreated as far as it’s going to this season. That’s based on satellite data – and, this year, eyewitness accounts.

“Right now,” says Chief Scientist Jennifer MacKinnon, “I’m standing on the bridge as we’re approaching the remnants of the ice pack. A lot of which has already melted, this summer, but we’re approaching one of the larger chunks of it that’s still in this area.”

Before the storm: The R/V Sikuliaq first encountered sea ice about 50 miles north of Alaska during this research cruise.
Credit Thomas Moore

MacKinnon is a researcher with the Scripps Institute of Oceanography at the University of California-San Diego. She called by sat-phone last week from a point about 50 miles north of Alaska that, at the time, was being battered by high winds and waves.

“One of the things we’ve gotten really excited about this week is that we’re seeing (that) the more the ice has melted in storms like the one we’re currently experiencing out here, there’s a lot of turbulent mixing of the upper ocean.”

Lead Scientist Jennifer MacKinnon operates controls of equipment that's been deployed from the Sikuliaq to monitor the turbulent mixing of warmer subsurface water with cooler surface water.
Credit Thomas Moore

MacKinnon is conducting much of her research in the Arctic Ocean under those conditions. Studying how that turbulence mixes relatively warm subsurface water with colder water at the surface. And how that contributes to the rapid rate of sea-ice melting.

“One of the funny things about the Arctic is that there’s a reservoir of heat beneath the surface here,” she said.

“So the more the wind is blowing on the ocean, the more it’s mixing this heat upwards. Which is bringing warmer water to the surface at a pretty rapid rate, warming the surface and accelerating the rate at which this ice is melting.”

The National Snow and Ice Data Center says Arctic sea ice reached its 2015 minimum extent of 4.4 million square kilometers (1.7 million square miles) on Sept. 11. The orange line shows the average sea-ice extent on that date based on measurements taken from 1981 to 2010
Credit NSIDC

MacKinnon says the lack of sea ice changes the dynamics of that process by enabling the ocean to absorb more heat, creating a positive-feedback loop that begets more rapid sea ice melting.

“And if storms like this continue, as there’s more open water, more storms mean more exposed surface,” she said. “It will not only melt the ice in the summer, but delay the onset of fall ice formation and accelerate the onset of spring ice melting.”

The National Snow and Ice Data Center predicts this year’s minimum summer sea ice extent won’t break the record set in 2012. But will probably end up as the third- or fourth-greatest seasonal ice retreat on record.

Editor's note: Visit the Arctic Mix website for blogs, photos, videos and more information about this research cruise.