Arctic Air Spills South, Southern Air Spills North

Departure from average temperatures for Feb. 27, 2014, as forecast by the GFS model. (Source: Data/image obtained using Climate Reanalyzer™ http://cci-reanalyzer.org/, Climate Change Institute, University of Maine, USA.)

Baby, it’s cold outside — again, especially for residents of the Upper Midwest who’ve been beset with repeated Arctic blasts this winter.

But as in previous episodes, that’s only part of the story, as the graphic above illustrates. It shows the forecast departure from normal temperature over the Northern Hemisphere. Notice that while the eastern half of the United States is shivering, large parts of the higher latitudes are considerably warmer than normal.

Once again a loopy jet stream is to blame. Click on the thumbnail at right to see what it looks like.

The map shows the jet stream as forecast by the GFS model for today. A sharp trough of low pressure has dropped down across much of the eastern half of the United States, opening to door for Arctic air to spill south.

The latest Arctic blast comes on a day when the Royal Society and National Academy of Sciences have released an overview of climate change, written in non-scientific language and targeted at general audiences. I’m sure pundits will use the cold temperatures some people are experiencing in the United States to deride the report. But as the map above shows, they will be telling only part of the story.

The new report addresses the issue of cold snaps in a warming world. Here’s part of what it has to say:

Global warming is a long-term trend, but that does not mean that every year will be warmer than the previous one. Day to day and year to year changes in weather patterns will continue to produce some unusually cold days and nights, and winters and summers, even as the climate warms.

The report provides a clear, straightforward and relatively concise overview of the evidence for climate change, and what’s causing it. I recommend that you check it out, and also pass it along to anyone you know who is puzzled about the issue — including anyone shivering under the latest blanket of Arctic air and wondering what happened to global warming.

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New NASA Satellite Survey Reveals Dramatic Arctic Sea Ice Thinning

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NASA Finds Sea Ice Driving Arctic Air Pollutants

Bromine explosion on March 13, 2008 across the western Northwest Territories in Canada looking toward the Mackenzie Mountains at the horizon, which prevented the bromine from crossing over into Alaska. Image credit: NASA/JPL-Caltech/University of Bremen
› Full image and caption March 01, 2012

PASADENA, Calif. - Drastic reductions in Arctic sea ice in the last decade may be intensifying the chemical release of bromine into the atmosphere, resulting in ground-level ozone depletion and the deposit of toxic mercury in the Arctic, according to a new NASA-led study.

The connection between changes in the Arctic Ocean's ice cover and bromine chemical processes is determined by the interaction between the salt in sea ice, frigid temperatures and sunlight. When these mix, the salty ice releases bromine into the air and starts a cascade of chemical reactions called a "bromine explosion." These reactions rapidly create more molecules of bromine monoxide in the atmosphere. Bromine then reacts with a gaseous form of mercury, turning it into a pollutant that falls to Earth's surface.

Bromine also can remove ozone from the lowest layer of the atmosphere, the troposphere. Despite ozone's beneficial role blocking harmful radiation in the stratosphere, ozone is a pollutant in the ground-level troposphere.

A team from the United States, Canada, Germany, and the United Kingdom, led by Son Nghiem of NASA's Jet Propulsion Laboratory in Pasadena, Calif., produced the study, which has been accepted for publication in the Journal of Geophysical Research- Atmospheres. The team combined data from six NASA, European Space Agency and Canadian Space Agency satellites; field observations and a model of how air moves in the atmosphere to link Arctic sea ice changes to bromine explosions over the Beaufort Sea, extending to the Amundsen Gulf in the Canadian Arctic.

"Shrinking summer sea ice has drawn much attention to exploiting Arctic resources and improving maritime trading routes," Nghiem said. "But the change in sea ice composition also has impacts on the environment. Changing conditions in the Arctic might increase bromine explosions in the future."

The study was undertaken to better understand the fundamental nature of bromine explosions, which first were observed in the Canadian Arctic more than two decades ago. The team of scientists wanted to find if the explosions occur in the troposphere or higher in the stratosphere.

Nghiem's team used the topography of mountain ranges in Alaska and Canada as a "ruler" to measure the altitude at which the explosions took place. In the spring of 2008, satellites detected increased concentrations of bromine, which were associated with a decrease of gaseous mercury and ozone. After the researchers verified the satellite observations with field measurements, they used an atmospheric model to study how the wind transported the bromine plumes across the Arctic.  

The model, together with satellite observations, showed the Alaskan Brooks Range and the Canadian Richardson and Mackenzie mountains stopped bromine from moving into Alaska's interior. Since most of these mountains are lower than 6,560 feet (2,000 meters), the researchers determined the bromine explosion was confined to the lower troposphere.

"If the bromine explosion had been in the stratosphere, 5 miles [8 kilometers] or higher above the ground, the mountains would not have been able to stop it and the bromine would have been transported inland," Nghiem said.

After the researchers found that bromine explosions occur in the lowest level of the atmosphere, they could relate their origin to sources on the surface. Their model, tracing air rising from the salty ice, tied the bromine releases to recent changes in Arctic sea ice that have led to a much saltier sea ice surface.

In March 2008, the extent of year-round perennial sea ice eclipsed the 50-year record low set in March 2007, shrinking by 386,100 square miles (one million square kilometers) -- an area the size of Texas and Arizona combined. Seasonal ice, which forms over the winter when seawater freezes, now occupies the space of the lost perennial ice. This younger ice is much saltier than its older counterpart because it has not had time to undergo processes that drain its sea salts. It also contains more frost flowers -- clumps of ice crystals up to four times saltier than ocean waters -- providing more salt sources to fuel bromine releases.

Nghiem said if sea ice continues to be dominated by younger saltier ice, and Arctic extreme cold spells occur more often, bromine explosions are likely to increase in the future.

Nghiem is leading an Arctic field campaign this month that will provide new insights into bromine explosions and their impacts. NASA's Bromine, Ozone, and Mercury Experiment (BROMEX) involves international contributions by more than 20 organizations. The new studies will complement those of a previously conducted NASA field campaign, Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS), which is providing scientists with valuable data for studies of bromine.

This study was funded by NASA, the National Oceanic and Atmospheric Administration, the National Science Foundation, the Office of Naval Research, the International Polar Year Program, Environment Canada, the Natural Sciences and Engineering Council of Canada, the European Space Agency, the State of Bremen, the German Aerospace Center, and the European Organisation for the Exploitation of Meteorological Satellites.

For more information about NASA programs, visit: http://www.nasa.gov .

JPL is managed for NASA by the California Institute of Technology in Pasadena.
Additional media contacts: Sandra Hines, University of Washington, 206-543-2080; John Burrows, University of Bremen, 011-49-421-218-62100; Isabelle Compagnon, Environment Canada, 819-953-6959; Sean Moore, University of Manitoba, 204-474-7963; Lt. Cmdr. Michael Vancas, National Ice Center, 301-817-3941; Katja Tholen-Ihnen, University of Hamburg, 011-49-0-40-42838-7596.

Alan Buis 818-354-0474
Jet Propulsion Laboratory, Pasadena, Calif.
Alan.buis@jpl.nasa.gov

Dwayne Brown 202-358-1726
NASA Headquarters, Washington
Dwayne.c.brown@nasa.gov

2012-054

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Missing 'Ice Arches' Contributed to 2007 Arctic Ice Loss

Large, thick floes of ice can be seen breaking off of the Arctic sea ice cover before entering the Nares Strait in this Dec. 23, 2007 radar image from the European Space Agency's Envisat satellite.
Credit: European Space Agency
Larger image | View animation (GIF 52 Mb) | View animation (GIF 13 Mb) February 18, 2010

PASADENA, Calif. - In 2007, the Arctic lost a massive amount of thick, multiyear sea ice, contributing to that year's record-low extent of Arctic sea ice. A new NASA-led study has found that the record loss that year was due in part to the absence of "ice arches," naturally-forming, curved ice structures that span the openings between two land points. These arches block sea ice from being pushed by winds or currents through narrow passages and out of the Arctic basin.

Beginning each fall, sea ice spreads across the surface of the Arctic Ocean until it becomes confined by surrounding continents. Only a few passages -- including the Fram Strait and Nares Strait -- allow sea ice to escape.

"There are a couple of ways to lose Arctic ice: when it flows out and when it melts," said lead study researcher Ron Kwok of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "We are trying to quantify how much we're losing by outflow versus melt."

Kwok and colleagues found that ice arches were missing in 2007 from the Nares Strait, a relatively narrow 30- to 40-kilometer-wide (19- to 25-mile-wide) passage west of Greenland. Without the arches, ice exited freely from the Arctic. The Fram Strait, east of Greenland, is about 400 kilometers (249 miles) wide and is the passage through which most sea ice usually exits the Arctic.

Despite Nares' narrow width, the team reports that in 2007, ice loss through Nares equaled more than 10 percent of the amount emptied on average each year through the wider Fram Strait.

"Until recently, we didn't think the small straits were important for ice loss," Kwok said. The findings were published this month in Geophysical Research Letters.

"One of our most important goals is developing predictive models of Arctic sea ice cover," said Tom Wagner, cryosphere program manager at NASA Headquarters in Washington. "Such models are important not only to understanding changes in the Arctic, but also changes in global and North American climate. Figuring out how ice is lost through the Fram and Nares straits is critical to developing those models."

To find out more about the ice motion in Nares Strait, the scientists examined a 13-year record of high-resolution radar images from the Canadian RADARSAT and European Envisat satellites. They found that 2007 was a unique year – the only one on record when arches failed to form, allowing ice to flow unobstructed through winter and spring.

The arches usually form at southern and northern points within Nares Strait when big blocks of sea ice try to flow through the strait's restricted confines, become stuck and are compressed by other ice. This grinds the flow of sea ice to a halt. 

"We don't completely understand the conditions conducive to the formation of these arches," Kwok said. "We do know that they are temperature-dependent because they only form in winter. So there's concern that if climate warms, the arches could stop forming."

To quantify the impact of ice arches on Arctic Ocean ice cover, the team tracked ice motion evident in the 13-year span of satellite radar images. They calculated the area of ice passing through an imaginary line, or "gate," at the entrance to Nares Strait. Then they incorporated ice thickness data from NASA's ICESat to estimate the volume lost through Nares.

They found that in 2007, Nares Strait drained the Arctic Ocean of 88,060 square kilometers (34,000 square miles) of sea ice, or a volume of 60 cubic miles. The amount was more than twice the average amount lost through Nares each year between 1997 and 2009.

The ice lost through Nares Strait was some of the thickest and oldest in the Arctic Ocean.

"If indeed these arches are less likely to form in the future, we have to account for the annual ice loss through this narrow passage. Potentially, this could lead to an even more rapid decline in the summer ice extent of the Arctic Ocean," Kwok said.

For more information about NASA and agency programs, visit: http://www.nasa.gov .

JPL is managed for NASA by the California Institute of Technology in Pasadena.

Alan Buis 818-354-0474
Jet Propulsion Laboratory, Pasadena, Calif.
Alan.buis@jpl.nasa.gov

Kathryn Hansen 301-352-4638
NASA Goddard Space Flight Center, Greenbelt, Md.
Kathryn.h.hansen@nasa.gov

2010-056 

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