Recently observed change in Arctic temperatures and sea ice cover may be a harbinger of global climate changes to come, according to a recent NASA study. Satellite data -- the unique view from space -- are allowing researchers to more clearly see Arctic changes and develop an improved understanding of the possible effect on climate worldwide.
The Arctic warming study, appearing in the November 1 issue of the American Meteorological Society's Journal of Climate, shows that compared to the 1980s, most of the Arctic warmed significantly over the last decade, with the biggest temperature increases occurring over North America.
"The new study is unique in that, previously, similar studies made use of data from very few points scattered in various parts of the Arctic region," said the study's author, Dr. Josefino C. Comiso, senior research scientist at NASA's Goddard Space Flight Center, Greenbelt, Md. "These results show the large spatial variability in the trends that only satellite data can provide." Comiso used surface temperatures taken from satellites between 1981 and 2001 in his study.
The result has direct connections to NASA-funded studies conducted last year that found perennial, or year-round, sea ice in the Arctic is declining at a rate of nine percent per decade and that in 2002 summer sea ice was at record low levels. Early results indicate this persisted in 2003.
Researchers have suspected loss of Arctic sea ice may be caused by changing atmospheric pressure patterns over the Arctic that move sea ice around, and by warming Arctic temperatures that result from greenhouse gas buildup in the atmosphere.
Warming trends like those found in these studies could greatly affect ocean processes, which, in turn, impact Arctic and global climate, said Michael Steele, senior oceanographer at the University of Washington, Seattle. Liquid water absorbs the Sun's energy rather than reflecting it into the atmosphere the way ice does. As the oceans warm and ice thins, more solar energy is absorbed by the water, creating positive feedbacks that lead to further melting. Such dynamics can change the temperature of ocean layers, impact ocean circulation and salinity, change marine habitats, and widen shipping lanes, Steele said.
In related NASA-funded research that observes perennial sea-ice trends, Mark C. Serreze, a scientist at the University of Colorado, Boulder, found that in 2002 the extent of Arctic summer sea ice reached the lowest level in the satellite record, suggesting this is part of a trend. "It appears that the summer 2003 -- if it does not set a new record -- will be very close to the levels of last year," Serreze said. "In other words, we have not seen a recovery; we really see we are reinforcing that general downward trend." A paper on this topic is forthcoming.
According to Comiso's study, when compared to longer term ground-based surface temperature data, the rate of warming in the Arctic over the last 20 years is eight times the rate of warming over the last 100 years.
Comiso's study also finds temperature trends vary by region and season. While warming is prevalent over most of the Arctic, some areas, such as Greenland, appear to be cooling. Springtimes arrived earlier and were warmer, and warmer autumns lasted longer, the study found. Most importantly, temperatures increased on average by 1.22 degrees Celsius per decade over sea ice during Arctic summer. The summer warming and lengthened melt season appears to be affecting the volume and extent of permanent sea ice. Annual trends, which were not quite as strong, ranged from a warming of 1.06 degrees Celsius over North America to a cooling of .09 degrees Celsius in Greenland.
If the high latitudes warm, and sea ice extent declines, thawing Arctic soils may release significant amounts of carbon dioxide and methane now trapped in permafrost, and slightly warmer ocean water could release frozen natural gases in the sea floor, all of which act as greenhouse gases in the atmosphere, said David Rind, a senior researcher at NASA's Goddard Institute of Space Studies, New York. "These feedbacks are complex and we are working to understand them," he added.
The surface temperature records covering from 1981 to 2001 were obtained through thermal infrared data from National Oceanic and Atmospheric Administration satellites. The studies were funded by NASA's Earth Science Enterprise, which is dedicated to understanding the Earth as an integrated system and applying Earth System Science to improve prediction of climate, weather and natural hazards using the unique vantage point of space.
Seasons of Change: Evidence of Arctic Warming Grows
SYNOPSIS:
Experts have long regarded Earth's polar regions as early indicators for global climate change. But until the last few years, wide ranging, comprehensive research about overall polar conditions has been challenging to conduct. Now a more than twenty-year record of space based measurements has been analyzed by researchers at NASA's Goddard Space Flight Center. Based on their findings, evidence of a warming planet continues to grow.
CHANGING SEASONS, CHANGING ICE
Research and data collection of Arctic Ocean ice isn't easy. But in this sequence using data collected by a number of satellites from 1979 to 2003, we see how scientists have been able to stitch together a careful record of sea ice in that part of the world. In 2002 scientists recorded the lowest concentration of sea ice ever in The Arctic. While temperature changes vary across the vast expanse of The Arctic, overall trends suggest that decreasing ice concentrations are due to a significant increase in ocean warming, from rising surface temperatures to the total number of annual "melt days".
Less ice means more open water. More open water means greater absorption of solar energy. More absorption of solar energy means increased rates of warming in the ocean, which naturally tends to yield faster rates of ice loss.
The data used to create these images come from a variety of different instruments flying on a group of satellites; they include the scanning multi-channel microwave radiometer attached to the Nimbus 7 satellite, and the special sensor microwave imagers attached to the Defense Meteorological Satellite Program's F8, F11, and F13 satellites.
Part of the challenge for researchers was in the elimination of "bad data", from atmospheric interference to instrument calibration issues and more. One reason that data acquired by microwave detecting instruments such as those flying on the DMSP satellites is that microwaves can penetrate the cloud cover that frequently blankets the Arctic. One of the most apparent characteristics of Arctic ice is just how dynamic and complex an environment it is. Through continued research and gathering of data, scientists hope to achieve a better level of understanding about the processes at work in the cryosphere.
Read full story on http://www.nasa.gov/centers/goddard/news/topstory/2003/1023esuice.html
The Arctic warming study, appearing in the November 1 issue of the American Meteorological Society's Journal of Climate, shows that compared to the 1980s, most of the Arctic warmed significantly over the last decade, with the biggest temperature increases occurring over North America."The new study is unique in that, previously, similar studies made use of data from very few points scattered in various parts of the Arctic region," said the study's author, Dr. Josefino C. Comiso, senior research scientist at NASA's Goddard Space Flight Center, Greenbelt, Md. "These results show the large spatial variability in the trends that only satellite data can provide." Comiso used surface temperatures taken from satellites between 1981 and 2001 in his study.
The result has direct connections to NASA-funded studies conducted last year that found perennial, or year-round, sea ice in the Arctic is declining at a rate of nine percent per decade and that in 2002 summer sea ice was at record low levels. Early results indicate this persisted in 2003.
Researchers have suspected loss of Arctic sea ice may be caused by changing atmospheric pressure patterns over the Arctic that move sea ice around, and by warming Arctic temperatures that result from greenhouse gas buildup in the atmosphere.
Warming trends like those found in these studies could greatly affect ocean processes, which, in turn, impact Arctic and global climate, said Michael Steele, senior oceanographer at the University of Washington, Seattle. Liquid water absorbs the Sun's energy rather than reflecting it into the atmosphere the way ice does. As the oceans warm and ice thins, more solar energy is absorbed by the water, creating positive feedbacks that lead to further melting. Such dynamics can change the temperature of ocean layers, impact ocean circulation and salinity, change marine habitats, and widen shipping lanes, Steele said.
In related NASA-funded research that observes perennial sea-ice trends, Mark C. Serreze, a scientist at the University of Colorado, Boulder, found that in 2002 the extent of Arctic summer sea ice reached the lowest level in the satellite record, suggesting this is part of a trend. "It appears that the summer 2003 -- if it does not set a new record -- will be very close to the levels of last year," Serreze said. "In other words, we have not seen a recovery; we really see we are reinforcing that general downward trend." A paper on this topic is forthcoming.
According to Comiso's study, when compared to longer term ground-based surface temperature data, the rate of warming in the Arctic over the last 20 years is eight times the rate of warming over the last 100 years.
Comiso's study also finds temperature trends vary by region and season. While warming is prevalent over most of the Arctic, some areas, such as Greenland, appear to be cooling. Springtimes arrived earlier and were warmer, and warmer autumns lasted longer, the study found. Most importantly, temperatures increased on average by 1.22 degrees Celsius per decade over sea ice during Arctic summer. The summer warming and lengthened melt season appears to be affecting the volume and extent of permanent sea ice. Annual trends, which were not quite as strong, ranged from a warming of 1.06 degrees Celsius over North America to a cooling of .09 degrees Celsius in Greenland.
If the high latitudes warm, and sea ice extent declines, thawing Arctic soils may release significant amounts of carbon dioxide and methane now trapped in permafrost, and slightly warmer ocean water could release frozen natural gases in the sea floor, all of which act as greenhouse gases in the atmosphere, said David Rind, a senior researcher at NASA's Goddard Institute of Space Studies, New York. "These feedbacks are complex and we are working to understand them," he added.
The surface temperature records covering from 1981 to 2001 were obtained through thermal infrared data from National Oceanic and Atmospheric Administration satellites. The studies were funded by NASA's Earth Science Enterprise, which is dedicated to understanding the Earth as an integrated system and applying Earth System Science to improve prediction of climate, weather and natural hazards using the unique vantage point of space.
Seasons of Change: Evidence of Arctic Warming Grows
SYNOPSIS:
Experts have long regarded Earth's polar regions as early indicators for global climate change. But until the last few years, wide ranging, comprehensive research about overall polar conditions has been challenging to conduct. Now a more than twenty-year record of space based measurements has been analyzed by researchers at NASA's Goddard Space Flight Center. Based on their findings, evidence of a warming planet continues to grow.
CHANGING SEASONS, CHANGING ICE
Research and data collection of Arctic Ocean ice isn't easy. But in this sequence using data collected by a number of satellites from 1979 to 2003, we see how scientists have been able to stitch together a careful record of sea ice in that part of the world. In 2002 scientists recorded the lowest concentration of sea ice ever in The Arctic. While temperature changes vary across the vast expanse of The Arctic, overall trends suggest that decreasing ice concentrations are due to a significant increase in ocean warming, from rising surface temperatures to the total number of annual "melt days".
Less ice means more open water. More open water means greater absorption of solar energy. More absorption of solar energy means increased rates of warming in the ocean, which naturally tends to yield faster rates of ice loss.
The data used to create these images come from a variety of different instruments flying on a group of satellites; they include the scanning multi-channel microwave radiometer attached to the Nimbus 7 satellite, and the special sensor microwave imagers attached to the Defense Meteorological Satellite Program's F8, F11, and F13 satellites.
Part of the challenge for researchers was in the elimination of "bad data", from atmospheric interference to instrument calibration issues and more. One reason that data acquired by microwave detecting instruments such as those flying on the DMSP satellites is that microwaves can penetrate the cloud cover that frequently blankets the Arctic. One of the most apparent characteristics of Arctic ice is just how dynamic and complex an environment it is. Through continued research and gathering of data, scientists hope to achieve a better level of understanding about the processes at work in the cryosphere.
Read full story on http://www.nasa.gov/centers/goddard/news/topstory/2003/1023esuice.html
No comments:
Post a Comment