April 21, 2011

Scientists Tracking Black Carbon In The Arctic

Researchers from six countries are in the Arctic studying the potential role that soot, or black carbon, has on the rapidly changing Arctic climate.

Although the Arctic is typically viewed as a vast white wasteland, scientists believe a thin layer of soot is causing it to absorb more heat. They want to find out if that is the main reason for the recent rapid warming of the Arctic, which could have an impact on the world's climate for years to come.

Black carbon is produced by vehicle engines, aircraft emissions, burning forests and wood- and coal-burning stoves.

"Carbon is dark in color and absorbs solar radiation, much like wearing a black shirt on a sunny day. If you want to be cooler, you would wear a light-colored shirt that would reflect the sun's warmth," said Tim Bates, a research chemist at NOAA's Pacific Marine Environmental Laboratory (PMEL) in Seattle and co-lead of the U.S. component of the study.

"When black carbon covers snow and ice, the radiation is absorbed, much like that black shirt, instead of being reflected back into the atmosphere," explained Bates.

Scientists from The United States, Norway, Russia, Germany, Italy and China are a participating in the Coordinated Investigation of Climate-Cryosphere Interactions (CICCI) project. The team's goals are to coordinate more than a dozen research activities so they are done in tandem providing, for the first time, a vertical profile of black carbon's movement through the atmosphere, its deposition on snow and ice surfaces, and its affect on warming in the Arctic.

"The Arctic serves as the air conditioner of the planet," said Patricia Quinn of the National Oceanic and Atmospheric Administration (NOAA), and research chemist at Pacific Marine Environmental Laboratory (PMEL).

Heat from other regions of the Earth moves to the Arctic via circulating air and ocean currents, where some of that warmth does radiate into space along its journey. At the same time, some of the incoming heat from the sun that tends to be absorbed in other regions is reflected by ice and snow, allowing the polar regions to help cool the planet.

But soot in the Arctic could be changing that game.

In recent years, the Arctic has been warming more rapidly than other areas of the planet and the "warming of the Arctic has implications not just for polar bears, but for the entire planet," Quinn told the Associated Press (AP).

"We need to better understand the behavior of black carbon in the Arctic," said Quinn. "This coordinated study will give us a snapshot so we can see all of it at once."

For the NOAA part of the study, called Soot Transport, Absorption, and Deposition Study (STADS), conducted between April 7 and May 6, researchers are using two small unmanned aircraft outfitted with sensors to take samples of the air in the Arctic. 

The aircraft will measure aerosol size, number, light absorption and chemical composition. A PMEL sensor will also be outfitted on the aircraft for the first time.

Also, a Norwegian unmanned aircraft will measure incoming radiation from the sun and the reflectivity of snow and ice covered surfaces.

NOAA will also collect falling and newly fallen snow to check levels of black carbon and for chemical tracer analysis. Chemical tracers yield information on the source of the black carbon, which is necessary for creating strategies on how best to deal with the impact black carbon has on the Arctic climate.

Also, Robert Stone of the Cooperative Institute for Research in Environmental Sciences will lead a study to measure reflectivity using a snowmobile-pulled sled on Svalbard at the Holtadalfohna Plateau, Kongsfjord fast ice, and the sea ice north of Spitsbergen.

Cutting carbon dioxide and other greenhouse gases is the mainstay of any effort to fight global warming, especially within the Arctic, said Quinn.

But studies suggest that cutting the concentration of short-lived pollutants, such as soot, will reduce the rate of warming in the Arctic faster than cuts in carbon dioxide and other greenhouse gases, which last much longer in the atmosphere, she said.

The UN Environmental Program urged for cuts in soot emissions in February. The call came for a variety of reasons, including the threat to human health from inhaling it and the potential warming of the polar regions.

The Arctic Council, which represents eight countries that border the Arctic, is deciding whether to seek reductions in soot from other nations and will be using data from the new research project to help make its decisions.

The surface air temperature in the Arctic has increased about twice as fast as the global average rate over the past 100 years, Quinn told AP in an interview by email. "Over the past 50 years, annual average surface air temperatures have increased from 2 to 3 degrees Celsius (3.6 to 5.4 degrees Fahrenheit) in Alaska and Siberia. The annual average temperature globally has increased by about 0.7 degree C (1.3 F) over the same time period."

The Arctic warming has resulted in an earlier spring melt, a longer melting season, and a decrease in the extent of sea ice, she said. That raises concerns for polar bears, which depend on sea ice to hunt for food. When the highly reflective snow and ice melt, the darker surfaces of land and water that are beneath absorb more heat, adding to the growing global warming problem.

Soot's greatest effect in the Arctic is likely to be warming caused by the particles floating in the atmosphere, according to Jack Dibb, an atmospheric chemist at the University of New Hampshire. It may also reduce the reflectivity of the snow and ice enough to cause warming, but that is going to be harder to document, he said in a telephone interview with AP.

The NOAA team includes leaders Bates and Quinn, as well as PMEL engineers Scott Stalin, Nick Delich, and Dirk Tagawa; Joint Institute for the Study of Atmosphere and Ocean scientists Jim Johnson and Drew Hamilton, and NOAA scientist Derek Coffman.

Participating institutions and research centers include the Arctic and Antarctic Research Institute, the Alfred Wegner Institute, the Institute of Atmospheric Sciences and Climate of the Italian National Research Council, the Chemistry Department of Florence University, the Norwegian Institute for Air Research, the Northern Research Institute, the Norwegian Institute for Polar Research, and the Chinese Academy of Meteorological Sciences.


Image 2: Trish Quinn shows off the first snow pit. Credit: NOAA-STAD


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