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."
