On thin ice

A team of UW scientists has been studying weather and changes in the Arctic for years, and the conclusion is clear: Arctic sea ice has been thinner in 2012 than in any previous year.

“Everybody talks about the extent of the sea ice, but thickness is really as important,” said Ron Lindsay, the senior principal physicist of the Polar Science Center (PSC), one of the departments of the UW Applied Physics Laboratory (APL). Lindsay also works with NASA’s Operation IceBridge, a program that studies the changing polar ice.

Employing a model developed at the APL/PSC called Pan-Arctic Ice-Ocean Modeling and Assimilation System (PIOMAS), Lindsay and others have analyzed and measured sea ice volume relative to the averages from 1979 to 2011. According to the most recent report, September ice volume was 800 cubic kilometers less than the previous minimum volume in 2011.
Although this measurement was within the uncertainty estimate of PIOMAS, the average ice thickness between March and August of 2012 was the smallest ever measured within the area PIOMAS studies.

“The biggest challenge is measuring ice thickness,” Lindsay said. “Satellites can measure the extent well, but measuring thickness was only accomplished with submarines or moorings in the past.”

The measurements, among others, are taken during monthly trips to the Arctic by various scientists. The U.S. Coast Guard flies regularly over the ever-growing expanse of open Arctic water, and UW researchers seize the opportunity to study changes in the region.

“It’s really a unique opportunity to work with the U.S. Coast Guard,” said Axel Schweiger, the principal scientist and chair of the PSC.

Deploying buoys, weather probes that can fly on programmed paths, and other tools, the UW researchers can gather a wealth of data that then must be analyzed with models specifically tailored to the task.

“One of the things that we look for are better models,” Schweiger said. “Current Intergovernmental Panel on Climate Change (IPCC) models can show less sea ice loss [than observed].”

Ensuring accurate results, especially in comparison to historical averages, requires careful computation and interpretation of results, which is where people such as Lindsay come in. By uniting observations made by the UW and other institutions and teams that study the Arctic, and utilizing the past seven summers’ data to build ensemble forecasts, models can be built to predict future changes in the region.

“This year we made a special effort to predict what the ice will do this fall,” Lindsay said. “I’ve been revising the proofs of September ice extent. But there’s always a lot of variability and we have to see how it plays out.”

The models do not always predict the future perfectly, and as shown by the difference in opinion among various institutions around the world, agreement is not always possible regarding how drastic the transformation of the Arctic region is.

However, the last summer’s worldwide prolonged heat and drought led to a startling new low. The average low point of Arctic sea ice from 1979 to 2000 was 7 million square kilometers, yet 2012’s ice ebbed all the way down to 3.4 million square kilometers. The UW team saw far more open stretches of water as they flew past in the Coast Guard’s C-130 Hercules planes. Although the last flight departed Oct. 17, the monthly trips since May gave the UW team plenty of numbers to analyze.

“We have to stop for winter as it gets so dark and cold,” said Mike Steele, the senior principal oceanographer at the APL. “We’re hoping to get approval from the Coast Guard to employ new buoys and more instruments over the winter.”

The rapidly changing face of the Arctic requires more understanding, hence the need for more sophisticated equipment. Changes in the climate lead to warmer ocean air, which, according to standard hypothesis — although Schweiger stated that nobody is quite sure — can lead to more clouds. These clouds exert a type of thermal blanket over the ice, shielding it from radiation, but also trapping heat, which melts the ice. The cycle of feedback is complex and requires much study, but the stakes are quite high.

“The overall goal is to understand what changes are occurring in the Arctic region and what those changes mean,” Steele said.

Reach reporter Garrett Black at science@dailyuw.com. Twitter: @garrettjblack