NASA Sees Rapid Changes in Arctic Sea Ice

This satellite image released by NASA shows the concentration of Arctic sea ice in 2005. Arctic sea ice in winter is melting far faster than before

Sept. 13, 2006-NASA data shows that Arctic perennial sea ice, which normally survives the summer melt season and remains year-round, shrunk abruptly by 14 percent between 2004 and 2005. According to researchers, the loss of perennial ice in the East Arctic Ocean neared 50 percent during that time as some of the ice moved from the East Arctic to the West.

NASA QuikScat shows inter annual observations of sea ice over the Arctic enabling the detection of recent drastic reductions in the extent of perennial ice and its depletion from the eastern Arctic Ocean between 2004, left and 2005. Arctic sea ice in winter is melting far faster than before, two new NASA studies reported Wednesday, a new and alarming trend that researchers say threatens the ocean's delicate ecosystem. For more than 25 years Arctic sea ice has slowly diminished in winter by about 1.5 percent per decade. But in the past two years the melting has occurred at rates 10 to 15 times faster.

The overall decrease in winter Arctic perennial sea ice totals 280,000 square miles--an area the size of Texas. Perennial ice can be 10 or more feet thick. It was replaced by new, seasonal ice only about one to seven feet thick that is more vulnerable to summer melt.

The decrease in the perennial ice raises the possibility that Arctic sea ice will retreat to another record low extent this year. This follows a series of very low ice-cover years observed over the past four summers from active and passive microwave satellite data.

A team led by Son Nghiem of NASA's Jet Propulsion Laboratory, Pasadena, Calif., used NASA's QuikScat satellite to measure the extent and distribution of perennial and seasonal sea ice in the Arctic. While the total area of all the Arctic sea ice was stable in winter, the distribution of seasonal and perennial sea ice changed significantly.

"Recent changes in Arctic sea ice are rapid and dramatic," said Nghiem. "If the seasonal ice in the East Arctic Ocean were to be removed by summer melt, a vast ice-free area would open up. Such an ice-free area would have profound impacts on the environment, as well as on marine transportation and commerce."

The researchers are examining what caused the rapid decrease in the perennial sea ice. Data from the National Centers for Environmental Prediction, Boulder, Colo., suggest that winds pushed perennial ice from the East to the West Arctic Ocean (primarily located above North America) and significantly moved ice out of the Fram Strait, an area located between Greenland and Spitsbergen, Norway. This movement of ice out of the Arctic is a different mechanism for ice shrinkage than the melting of Arctic sea ice, but it produces the same results - a reduction in the amount of perennial Arctic sea ice.

Researchers indicate that if the sea ice cover continues to decline, the surrounding ocean will get warmer, further accelerating summer ice melts and impeding fall freeze-ups. This longer melt season will, in turn, further diminish the Arctic ice cover.

Nghiem cautioned the recent Arctic changes are not well understood and many questions remain. "It's vital that we continue to closely monitor this region, using both satellite and surface-based data," he said.

This is one of three study results being released today by NASA. The findings are the result of a new study by NASA; the U.S. Army Cold Region Research and Engineering Laboratory, Hanover, N.H.; and the National Ice Center, Washington, D.C. Study results are published in a recent issue of Geophysical Research Letters.

Arctic Sea Ice Hitting Major Lows in Wintertime

09.13.06

The Arctic winter wonderland, known for its icy waterways and white snowy scenery, is experiencing record low sea ice in the last two years. In a new NASA study, scientists have used satellite observations to observe unusually warm wintertime temperatures in the region and a resulting decline in the length of the Arctic ice season.

The maximum amount of sea ice in the Arctic winter has fallen by six percent over each of the last two winters, as compared to a loss of merely 1.5 percent per decade on average annually since the earliest satellite monitoring in 1979. This is happening as summer sea ice continues its retreat at an average of 10 percent per decade. This amount of Arctic sea ice reduction the past two consecutive winters has not taken place before during the 27 years satellite data has been available," said Joey Comiso, a research scientist at NASA's Goddard Space Flight Center, Greenbelt, Md. "In the past, sea ice reduction in winter was significantly lower per decade compared to summer sea ice retreat. What's remarkable is that we've witnessed sea ice reduction at six percent per year over just the last two winters, most likely a result of warming due to greenhouse gases."

Comiso used a computer simulation and satellite data to carry out the study, to be published in Geophysical Research Letters this month.

Computer simulations of the climate warming effect of greenhouse gases had predicted that winter sea ice would decline faster than summer sea ice. Satellite data has shown otherwise until two years ago, when record low winter ice cover and warmer temperatures have prevailed.

Sea ice cover in the Northern Hemisphere spans nearly 10 million square miles in the winter. Satellite sensors are the only means to observe such a large region effectively. Comiso confirmed the accuracy of satellite sea ice data by comparing it with high-resolution satellite information and data gathered from sensitive instruments aboard aircraft. Surface temperature data from satellite sensors are checked against measurements from meteorological stations in the region.

Adding to the plight of winter sea ice, previous research has shown a trend in which the melt period lasts about 2 weeks longer per year annually due to summer sea ice decline.

According to Comiso, if the winter ice retreat continues, the effect could be very profound, especially for marine animals. "The seasonal ice regions in the Arctic are among the most biologically productive regions in the world," he said. "For example, sea ice provides melt-water in spring that floats because of low density. This melt-water layer is considered by biologists as the ideal layer for phytoplankton growth because it does not sink, and there is plenty of sunlight reaching it to enable photosynthesis. Plankton are at the bottom of the food web. If their concentration goes down, animals at all tropics level would be deprived of a basic source of food." "A continued reduction of the Arctic winter ice cover would be a clear indicator of the warming effect of increasing greenhouse gases in the atmosphere. It would at least confirm our current understanding of the physics of the Arctic climate system that has been incorporated in our models," said Comiso.

Slow Retreat of Sea Ice Lengthens Arctic Polar Bear's Fast

09.13.06

Many of us have watched documentary film clips or seen touching photos of mother polar bears walking on the icy surface of Arctic waters, at times with cubs in tow, hunting for food. For some time, scientists have suggested that the same icy Arctic surface -- sea ice -- is slowly retreating because of an ever-warming climate.

Scientists from NASA and the Canadian Wildlife Service are now reporting that the slow reduction in sea ice is forcing Arctic polar bears to fast for longer and longer periods, posing danger to their survival.

Claire Parkinson, a senior scientist at NASA's Goddard Space Flight Center, and Ian Stirling, a research scientist specializing in polar marine mammals with the Canadian Wildlife Service in Edmonton, Alberta, also suggest that the progressively earlier breakup of sea ice, caused by climate warming, shortens the spring hunting season for female polar bears and is probably responsible for the observed weight loss in these bears. The lighter the females, the more their ability to reproduce, and ability for their young to survive declines.

As the bears become thinner, they will also have a greater tendency to seek alternative food villages and hunting camps, giving the impression to some that the population is increasing. The study will be published this week in the September issue of the Journal Arctic.

"A key result of our research is its strong suggestion that climate warming is having a significant and negative effect on a primary species reliant on the sea ice cover for survival," said Parkinson.
The researchers used NASA satellite observations captured over 26 years from 1979 to 2004 to show the reduction in sea ice cover in several specific areas. In most of the areas studied, they found that ice break-up in these areas has been occurring progressively earlier over time.

"Polar bears live much of their lives on the sea ice, which is fundamental for their survival, at least in terms of their traditional lifestyles. For instance, it�s the sea ice surface that provides them a platform from which to hunt seals and other marine mammals for food," said Parkinson. Sea ice is most scarce during the summer months, causing the bears to retreat to land and fast on their stored fat reserves until sea ice comes back in the fall.

"By reviewing satellite data, we found that sea ice cover break-up in Western Hudson Bay took place at about seven to eight days earlier per decade," said Stirling. "An extra month of fasting resulting from this phenomenon over four decades can significantly impact the polar bears' eating habits and survival."

The researchers' data also indicate the likelihood that progressively earlier breakup of the sea ice was likely to also cause reproductive problems for polar bears.

"In 1980 the average weight of adult females in western Hudson Bay was 650 pounds. Their average weight in 2004 was just 507 pounds � a 143-pound reduction," said Stirling. A 1992 study in the Canadian Journal of Zoology indicated that no females weighing less than 416 pounds gave birth the following spring.

According to Stirling, if the climate continues to warm as projected by the Intergovernmental Panel on Climate Change and the ice continues to break up progressively earlier, it is likely that in another 20-30 years polar bear reproduction in western Hudson Bay will be significantly limited and may be repeated elsewhere.