Showing posts with label ARTIC. Show all posts
Showing posts with label ARTIC. Show all posts

Friday, April 26, 2013

THE CHEMISTRY OF SUN AND SNOW IN THE ARTIC

Artic Sun.  U.S. Fish And Wildlife Service
FROM: NATIONAL SCIENCE FOUNDATION

Sunlit Snow Triggers Atmospheric Cleaning, Ozone Depletion in the Arctic

Finding is related to snow atop sea ice, adding a new dimension to scientific concerns about loss of Arctic ice

National Science Foundation-funded researchers at Purdue University have discovered that sunlit snow is the major source of atmospheric bromine in the Arctic, the key to unique chemical reactions that purge pollutants and destroy ozone.

The new research also indicates that the surface snowpack above Arctic sea ice plays a previously unappreciated role in the bromine cycle and that loss of sea ice, which been occurring at an increasingly rapid pace in recent years, could have extremely disruptive effects in the balance of atmospheric chemistry in high latitudes.

The team's findings suggest the rapidly changing Arctic climate--where surface temperatures are rising three times faster than the global average--could dramatically change its atmospheric chemistry, said Paul Shepson, an NSF-funded researcher who led the research team. The experiments were conducted by Kerri Pratt, a postdoctoral researcher funded by the Division of Polar Programs in NSF's Geosciences Directorate.

"We are racing to understand exactly what happens in the Arctic and how it affects the planet because it is a delicate balance when it comes to an atmosphere that is hospitable to human life," said Shepson, who also is a founding member of the Purdue Climate Change Research Center. "The composition of the atmosphere determines air temperatures, weather patterns and is responsible for chemical reactions that clean the air of pollutants."

A paper detailing the results of the research, some of which was funded by NSF and some by the National Aeronautics and Space Administration, was recently published online at Nature Geoscience.


Arctic Sea Ice.  Credit:  NOAA.

Ozone in the lower atmosphere behaves differently from the stratospheric ozone involved in the planet's protective ozone layer. This lower atmosphere ozone is a greenhouse gas that is toxic to humans and plants, but it also is an essential cleaning agent of the atmosphere.

Interactions between sunlight, ozone and water vapor create an "oxidizing agent" that scrubs the atmosphere of most of the pollutants human activity releases into it, Shepson said.

Temperatures at the poles are too cold for the existence of much water vapor and in the Arctic this cleaning process appears instead to rely on reactions on frozen surfaces involving molecular bromine, a halogen gas derived from sea salt.

This gaseous bromine reacts with and destroys atmospheric ozone. This aspect of the bromine chemistry works so efficiently in the Arctic that ozone is often entirely depleted from the atmosphere above sea ice in the spring, Shepson noted.

"This is just a part of atmospheric ozone chemistry that we don't understand very well, and this unique Arctic chemistry teaches us about the potential role of bromine in other parts of the planet," he said. "Bromine chemistry mediates the amount of ozone, but it is dependent on snow and sea ice, which means climate change may have important feedbacks with ozone chemistry."

While it was known that there is more atmospheric bromine in polar regions, the specific source of the natural gaseous bromine has remained in question for several decades, said Pratt, a Polar Programs-funded postdoctoral fellow and lead author of the paper.

"We thought that the fastest and best way to understand what is happening in the Arctic was to go there and do the experiments right where the chemistry is happening," Pratt said.

She and Purdue graduate student Kyle Custard performed the experiments in -45 to -34 Celsius (-50 to -30 Fahrenheit) wind chills near Barrow, Alaska. The team examined first-year sea ice, salty icicles and snow and found that the source of the bromine gas was the top surface snow above both sea ice and tundra.

"Sea ice had been thought to be the source of the gaseous bromine," she said. "We had an 'of course!' moment when we realized it was the snow on top of the sea ice. The snow is what is in direct contact with the atmosphere. Sea ice is critical to the process, though. Without it, the snow would fall into the ocean, and this chemistry wouldn't take place. This is among the reasons why the loss of sea ice in the Arctic will directly impact atmospheric chemistry."

The team also discovered that sunlight triggered the release of bromine gas from the snow and the presence of ozone increased the production of bromine gas.

"Salts from the ocean and acids from a layer of smog called Arctic haze meet on the frozen surface of the snow, and this unique chemistry occurs," Pratt said. "It is the interface of the snow and atmosphere that is the key."

A series of chemical reactions that quickly multiplies the amount of bromine gas present, called the "bromine explosion," is known to occur in the atmosphere. The team suggests this also occurs in the spaces between the snow crystals and wind then releases the bromine gas up into the air above the snow.

The team performed 10 experiments with snow and ice samples contained in a "snow chamber," a box constructed of aluminum with a special coating to prevent surface reactions and a clear acrylic top. Clean air with and without ozone was allowed to flow through the chamber and experiments were performed in darkness and in natural sunlight.

The team also measured the levels of bromine monoxide, a compound formed from the reaction of bromine atoms with ozone, through flights of the Purdue Airborne Laboratory for Atmospheric Research.

Shepson is the pilot of this specially equipped aircraft, which he and air operations technical specialist Brian Stirm flew from Indiana to Barrow for these experiments. They found the compound was most prevalent over snow-covered first-year sea ice and tundra, consistent with their snow chamber experiments.

The experiments were performed from March to April 2012 and were part of NASA's Bromine, Ozone and Mercury Experiment, or BROMEX. The goal of the study is to understand the implications of Arctic sea ice reduction on tropospheric chemistry.

Shepson's group next plans to perform laboratory studies to test the proposed reaction mechanisms and to return to Barrow to perform more snow chamber experiments.

In addition, Shepson is co-leading a team using ice-tethered buoys to measure carbon dioxide, ozone and bromine monoxide across the Arctic Ocean, and Pratt is working with scientists from the University of Washington to examine the chemistry of snow from across the Arctic Ocean.

"In the Arctic, climate change is happening at an accelerated pace," Pratt said. "A big question is what will happen to atmospheric composition in the Arctic as the temperatures rise and snow and ice decline even further?"

-NSF-

Saturday, April 20, 2013

BAFFIN ISLAND OVERFLIGHT BY P-3B




FROM: NASA
IceBridge Flight Over Baffin Island

IceBridge closed out the fourth week of its Arctic campaign with a flight over the striking landscape of eastern Greenland's Geikie Peninsula and a survey of a Canadian ice cap before taking two days off over the weekend. Soon the mission will return to Thule to finish up Arctic flights for 2013.

The morning of April 12, 2013 saw the P-3B take off for a flight to the west, across the Davis Strait to Canada's Baffin Island. This island, the largest one in Canada, is home to an ice formation known as the Penny Ice Cap. This mission was a repeat of airborne surveys by the ATM and radar teams flown in 1995, 2000 and 2005, and added new survey lines along ICESat ground tracks. Previous airborne surveys showed the ice cap thinning and glaciers retreating in the area and the April 12 mission aimed at measuring several glaciers in the area to see how much the Penny Ice Cap has melted in recent years.

The image captures ice covered fjord on Baffin Island with Davis Strait in the background. Image Credit-NASA-Michael Studinger

Friday, April 12, 2013

THE GREENING OF THE ARTIC

Photo:  Melting Artic Ice.  Credit:  NOAA
FROM: NATIONAL SCIENCE FOUNDATION
New Models Predict Dramatically Greener Arctic in the Coming Decades

Rising temperatures will lead to a massive "greening" of the Arctic by mid-century, as a result of marked increases in plant cover, according to research supported by the National Science Foundation (NSF) as part of its International Polar Year (IPY) portfolio.

The greening not only will have effects on plant life, the researchers noted, but also on the wildlife that depends on vegetation for cover. The greening could also have a multiplier effect on warming, as dark vegetation absorbs more solar radiation than ice, which reflects sunlight.

In a paper published March 31 in Nature Climate Change, scientists reveal new models projecting that wooded areas in the Arctic could increase by as much as 50 percent over the coming decades. The researchers also show that this dramatic greening will accelerate climate warming at a rate greater than previously expected.

"Such widespread redistribution of Arctic vegetation would have impacts that reverberate through the global ecosystem," said Richard Pearson, lead author on the paper and a research scientist at the American Museum of Natural History's Center for Biodiversity and Conservation.

In addition to Pearson, the research team includes other scientists from the museum, as well as from AT&T Labs-Research, Woods Hole Research Center, Colgate and Cornell universities, and the University of York.

The research was funded by two related, collaborative NSF IPY grants, one made to the museum and one to the Woods Hole Researc Center.

IPY was a two-year, global campaign of research in the Arctic and Antarctic that fielded scientists from more than 60 nations in the period 2007-2009. The IPY lasted two years to insure a full year of observations at both poles, where extreme cold and darkness preclude research for much of the year. NSF was the lead U.S. government agency for IPY.

Although the IPY fieldwork has been largely accomplished "in addition to the intensive field efforts undertaken during the IPY, projects such as this one work to understand IPY and other data in a longer-term context, broadening the impact of any given data set," said Hedy Edmonds, Arctic Natural Sciences program director in the Division of Polar Programs of NSF's Geosciences Directorate.

Plant growth in Arctic ecosystems has increased over the past few decades, a trend that coincides with increases in temperatures, which are rising at about twice the global rate.

The research team used climate scenarios for the 2050s to explore how the greening trend is likely to continue in the future. The scientists developed models that statistically predict the types of plants that could grow under certain temperatures and precipitation. Although it comes with some uncertainty, this type of modeling is a robust way to study the Arctic because the harsh climate limits the range of plants that can grow, making this system simpler to model compared to other regions, such as the tropics.

The models reveal the potential for massive redistribution of vegetation across the Arctic under future climate, with about half of all vegetation switching to a different class and a massive increase in tree cover. What might this look like? In Siberia, for instance, trees could grow hundreds of miles north of the present tree line.

These impacts would extend far beyond the Arctic region, according to Pearson.

For example, some species of birds migrate from lower latitudes seasonally, and rely on finding particular polar habitats, such as open space for ground-nesting.

The computer modeling for the project was supported by a separate NSF grant to Cornell by the Division of Computer and Network Systems in NSF's Directorate for Computer & Information Science & Engineering, as part of the directorate's Expeditions in Computing program.

"The Expeditions grant has enabled us to develop sophisticated probabilistic models that can scale up to continent-wide vegetation prediction and provide associated uncertainty estimates. This is a great example of the transformative research happening within the new field of Computational Sustainability," said Carla P. Gomes, principal investigator at Cornell.

In addition to the first-order impacts of changes in vegetation, the researchers investigated the multiple climate-change feedbacks that greening would produce.

They found that a phenomenon called the albedo effect, based on the reflectivity of the Earth's surface, would have the greatest impact on the Arctic's climate. When the sun hits snow, most of the radiation is reflected back to space. But when it hits an area that's "dark," or covered in trees or shrubs, more sunlight is absorbed in the area and temperature increases. This has a positive feedback to climate warming: the more vegetation there is, the more warming will occur.

"By incorporating observed relationships between plants and albedo, we show that vegetation distribution shifts will result in an overall positive feedback to climate that is likely to cause greater warming than has previously been predicted," said co-author and NSF grantee Scott Goetz, of the Woods Hole Research Center.

-NSF-

Friday, September 7, 2012

TAKING THE 'POLAR BEAR PLUNGE'






FROM:  U.S. AIR FORCE
09/4/2012 - THULE AIR BASE, Greenland – Icebergs float on the horizon as 821st Air Base Group Airmen hold a polar bear swim Aug. 4 and 26 at the Thule AB Tug Boat Beach. The air temperature was 51 degrees, while the water was a scant 41 degrees. "It was a really unique experience," said a chilled Staff Sgt. Neal Thompson, 821st Air Base Group Knowledge Operations Management. "It was definitely something that a lot of people are unable to do," he said referring to his newly-earned title of Polar Bear. Thule AB is one of the six installations operated by the 21st Space Wing, and is located 750 miles north of the Arctic Circle. (U.S. Air Force photo/ Staff Sgt. Laura Vargas)

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