Arctic Expedition Digs Into Ice Melt Puzzle

/ Source: OurAmazingPlanet

This month, a plucky band of scientists and explorers is headed to a remote floating base in the Arctic Ocean, where they will spend the coming weeks living out on the sea ice, searching for clues to help solve a climate mystery: Why is the Arctic's ice melting faster than anyone predicted?

The adventurers will brave frigid weather and sleep in unheated tents. Victoria Hill, a scientist who usually lives in the far more tender-footed climes of Virginia, said enduring the extreme conditions will be worth it.

Acknowledging the risk of sounding like "a total geek," Hill said: "I'm really looking forward to getting my hands on some data. It's really exciting — what am I going to find?"

See what?

Hill, a research assistant professor at the Department of Ocean, Earth and Atmospheric Sciences at Norfolk's Old Dominion University, is after a little-studied and ill-understood player in the ice-melt game — something called colored dissolved organic matter, or CDOM.

Intense study of CDOM (pronounced SEE-dahm) began only in the last decade or so. CDOM, which comes from broken down organic material, as the name implies, appears in oceans around the world and is known to trap the sun's rays, heating the water around it. However, much about CDOM, which appears when living things are broken down remains mysterious.

"When you measure CDOM you can't get a concentration," Hill told OurAmazingPlanet. "You can't get ‘x’ grams per liter."

Even though "pieces" of CDOM are minuscule, each about the size of a virus, satellites can map CDOM's distribution throughout the world's oceans because of the material’s ability to absorb solar radiation.

However, in the Arctic, sea ice obscures ocean water — and thus any CDOM it may contain — from satellite view. So unknown quantities of CDOM could be absorbing unknown amounts of solar radiation, which could be further fueling ice melt.

"I think these surface waters are absorbing a lot more solar energy than we've accounted for," Hill said. "Ice in the Arctic has been melting much more rapidly than all the models predicted, so obviously we're missing some process that we haven't incorporated into the models."

See ice disappear

"This is the right thing to measure," said Mark Serreze, director of the National Snow and Ice Data Center at the University of Colorado at Boulder.

Satellite measurements that began in 1979 show that Arctic sea ice cover has been declining steadily. Serrezze said greenhouse gas emissions and the warming they cause account for much of the ever-increasing melting.

"It's part of a feedback model," Serrezze told OurAmazingPlanet. The sea ice is melting earlier in the year, exposing ocean areas earlier. The open water is darker than the ice, and absorbs more solar energy, Serreze said, heating the water and melting more ice.

However, ignorance remains about the underlying mechanisms for all this accelerated melting, and heat-trapping CDOM could be one of the culprits.

As to the ultimate fate of the Arctic's sea ice, Serreze said there is overwhelming evidence the region eventually will be virtually ice-free in the summer months — perhaps within the next 20 or 30 years.

"So the question is not 'if,' the question is 'when,’" Serreze said. In the meantime, he said, finding data and working the correct mechanisms into climate models is a priority. "That is very much a part of coming up with the answer as to when we will lose the ice," he said.

Sea ice data

Hill, along with several other researchers and explorers from the United Kingdom and the United States, is slated to reach the expedition's isolated base off Ellef Ringnes Island in the Canadian Arctic by mid-March.

The voyage is part of the Catlin Arctic Survey, a privately sponsored endeavor now in its third year, aimed at examining climate change effects in the Arctic and how they will affect the rest of the world.

Hill and a colleague from Old Dominion plan to spend 46 days out on the ice — the longest period for any scientists taking part in the trip. Using various instruments, they will look into how much CDOM is in the water and try to figure out where it's coming from.

"I think it's sea ice algae, but we don't have any real proof of that right now," Hill said.

It's also possible the dissolved organic matter is coming from land, carried by the mighty rivers that empty into the Arctic's ocean waters.

Or, Hill said, it could be some unknown combination of the two. Either way, the source of the CDOM has big implications for the future of Arctic sea ice.

"If the CDOM is forming from the ice, as we see less sea ice forming every winter we could see a reduction in the CDOM," Hill said. "So the heating could decrease, which might slow the melting of the ice."

However, Hill said, if the CDOM is coming from land, the opposite could be true. "As we see more vegetative growth on land because it's warmer — bringing a longer growing season and melting permafrost — then we could see an increase in the heating."

During the expedition, Hill will drill through the ice and take samples of both ice and water from the bottom of the ice floes down to a depth of some 300 meters (984 feet).

Subtle differences in the way CDOM absorbs light , and the abundance of chlorophyll within the samples, will help Hill begin to unlock whether the CDOM's ultimate source is marine or terrestrial.

"By the time we leave the ice camp, we'll have six weeks of data and will have an idea of which direction it's going in," Hill said.

Ice life

Although data are the main attraction on this trip, Hill is far from immune to the pull of Arctic adventure.

The enforced high-calorie diet required by frozen living brings some small joys — "I'm told I can eat as much chocolate as I want," Hill said gleefully.

And the views are unmatched.

"I was so struck by the beauty the last time I was there," Hill said, recalling an expedition aboard an icebreaker in the Chukchi Sea in 2004.

"I'm looking forward to being out on the ice again. All you see is white for miles and miles, but it really is beautiful," Hill said. "I want to get up there before it's not there anymore."

Reach Andrea Mustain at Follow her on Twitter @AndreaMustain.