NASA Team Studies Pollutants' Effect on Arctic Climate Change

A NASA-led team completed April 21 the first of two planned field studies using airborne and space-based sensors to collect data that will help scientists better understand the impact of atmospheric pollutants on the Arctic's climate. Although analysis of the data has just begun, an initial finding is that fossil-fuel emissions that accumulate in the Arctic atmosphere come from all over the globe, according to scientists involved in the effort.

The Arctic has become an attractive region for scientific research as worldwide awareness of global climate change has increased in recent years. The growing body of research on climate change continues to show the planet's polar regions are undergoing the most rapid changes.

The Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) program is the most recent in a series of NASA field campaigns that have been studying atmospheric chemistry for two decades. The ARCTAS mission is part of the International Polar Year, an international collaboration involving more than 60 nations and 200 programs to study the Arctic and Antarctic regions. The U.S. Department of Energy and the National Oceanic and Atmospheric Administration also are contributing to the mission.

While much atmospheric research is dedicated to the long-term effects that carbon dioxide and other so-called greenhouse gases have on the atmosphere, the goal of ARCTAS is to understand how pollutants that remain in the atmosphere for a short time affect the Arctic climate. The two field studies are focused on two different pollutants: those generated from the burning of fossil fuels and those generated by the Arctic's summertime forest fires.

Using three heavily instrumented NASA planes in concert with data from six Earth-observing satellites, the ARCTAS team spent three weeks in Fairbanks, Alaska, studying fossil-fuel pollutants in the lower 12 kilometers of the atmosphere. The second part of the mission will take place this summer in Alberta, Canada, where the team will use the same methods to study the effects of pollutants generated by the seasonal forest fires in the Arctic.

The ARCTAS program will cost around $11 million this year and the team will spend another $5 million to $6 million in each of the next several years to analyze the data, Jim Crawford, NASA's ARCTAS program manager, said in a May 7 interview.

Since the Arctic is relatively unpopulated, it is known that most of the fossil-fuel pollutants found there came from lower latitudes. The spring is the best time to study pollutants there because the lack of sunlight during the winter allows them to accumulate the most, creating a phenomenon called Arctic haze.

Pollutants have an effect on the temperature of the atmosphere. Some particles, like sulfate, reflect a large amount of the sun's energy, creating a cooling effect on the atmosphere. Other particles, like the black carbon spewed by diesel trucks, absorb much of that energy and have a warming effect.

Other emissions found in the Arctic atmosphere, including ozone, methane, nitrogen oxides and water vapor, lie somewhere in between and only add to the complexity of the research. Because so many types of pollutants are created when fossil fuels are burned, understanding the net gain or loss of atmospheric heat is very difficult, Crawford said.

"We're looking at more short-term impacts of burning fossil fuels," Crawford said. "Carbon dioxide alone is important, but it's not a complete picture. The [Intergovernmental Panel on Climate Change] is even more certain of the effects of tropospheric ozone and particulate in the atmosphere."

The team is still in the process of validating its data and is not yet ready to present its findings. Eventually the data will be used to verify and improve climate change models. The one finding the team is certain of is pollutants found in the Arctic originate from every region of the planet and no single location appears to be the lone culprit.

"There is a disagreement about whether it is the fires in the Arctic or pollutants from other regions that are having the most fundamental impact," Crawford said. "I don't personally have a hypothesis. I just want to see what those impacts are."

Hanwant Singh, NASA's lead mission scientist, said this will be the most detailed study of the Arctic atmosphere ever produced because of the volume of data being collected and the highly advanced instruments being used. While many of the sensors on the planes and satellites have been operational for years, new instruments, some capable of detecting black carbon molecules and halogen radicals, for example, are generating previously unattainable data.

"We've brought in the latest technology," Singh said. "Many measurements we are taking were probably not possible 10 years ago."

While saying a three-week campaign produced a wealth of detailed atmospheric information, Crawford and Singh agreed a longer-term effort is needed. One tool on Crawford's wish list is a high-resolution atmospheric chemistry sensor operating in geostationary orbit. This would generate the kind of long-term data needed for change detection.

"We've never had geostationary measurements before," Crawford said. "It's something we are committed to, and we are actively talking about plans for one."

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