ScienceDaily -- Your link to the latest research news
  Search ScienceDaily:
  Find in   
  For advanced search options, click here.
  Subscribe for free email updates.
 Ad-Free
 Access:

 Click here
 to sign up,
 or log in.
Welcome!
 Home page
 About this site
 Awards, reviews
 Privacy policy

News Pages
 Summaries
 Headlines
 News by topic
 Find stories

Science Shop
 Browse books
 Magazines
 Software

Contribute
 Register free
 Post release
 Edit profile
 Review hits

Advertise
 Media kit
 Traffic stats
 Contact us
 
  Email
this story
  Printer-friendly
version
  Previous
story
  Next
story
 
Source:   NASA/Goddard Space Flight Center (http://www.gsfc.nasa.gov/)
Date:   Posted 8/23/2002

Satellites Show Overall Increases In Antarctic Sea Ice Cover

While recent studies have shown that on the whole Arctic sea ice has decreased since the late 1970s, satellite records of sea ice around Antarctica reveal an overall increase in the southern hemisphere ice over the same period. Continued decreases or increases could have substantial impacts on polar climates, because sea ice spreads over a vast area, reflects solar radiation away from the Earth's surface, and insulates the oceans from the atmosphere. In a study just published in the Annals of Glaciology, Claire Parkinson of NASA's Goddard Space Flight Center analyzed the length of the sea ice season throughout the Southern Ocean to obtain trends in sea ice coverage. Parkinson examined 21 years (1979-1999) of Antarctic sea ice satellite records and discovered that, on average, the area where southern sea ice seasons have lengthened by at least one day per year is roughly twice as large as the area where sea ice seasons have shortened by at least one day per year. One day per year equals three weeks over the 21-year period.

"You can see with this dataset that what is happening in the Antarctic is not what would be expected from a straightforward global warming scenario, but a much more complicated set of events," Parkinson said.

The length of the sea ice season in any particular region or area refers to the number of days per year when at least 15 percent of that area is covered by sea ice. Some areas close to the Antarctic continent have sea ice all year long, but a much larger region of the Southern Ocean has sea ice for a smaller portion of the year, and in those regions the length of the sea ice season can vary significantly from one year to another.

To calculate the lengths of the sea ice seasons, Parkinson used satellite data gridded to 25 by 25 kilometer grid cells for the Southern Ocean region. For each grid cell, the satellite data were used to determine the concentration, or percent area, of the sea ice cover. Whenever the percentage was at least 15 percent, the grid cell was considered to have ice. Using this method, Parkinson went through the entire data set and for each grid cell had a computer count how many days of each year had ice, then calculated trends over the 21-year record.

Overall, the area of the Antarctic with trends indicating a lengthening of the sea ice season by at least one day per year was 5.6 million square kilometers (2.16 million square miles), about 60 percent the size of the United States. At the same time, the area with sea ice seasons shortening by at least one day per year was 3 million square kilometers (1.16 million square miles).

Regionally, the Ross Sea, on average, had its sea ice seasons getting longer, while most of the Amundsen Sea and almost the entire Bellingshausen Sea had their sea ice seasons getting shorter.

"The Antarctic sea ice changes match up well with regional temperature changes," Parkinson said. "The one region in the Antarctic where the temperature records have shown prominent warming over this period is the Antarctic Peninsula, and indeed it's immediately to the west and east of the Antarctic Peninsula, in the Bellingshausen/Amundsen and western Weddell seas, respectively, that the sea ice seasons have been shortening rather than lengthening."

The Arctic also shows a mixed pattern of sea ice trends over the 1979-1999 period, but in contrast to the Antarctic, the area with shortening seasons in the Arctic is far greater than the area with lengthening seasons. The Arctic patterns suggest some connections with major oscillations in large-scale atmospheric pressures, called the Arctic Oscillation and the North Atlantic Oscillation, and it is possible the ice covers of both hemispheres could be influenced by oscillations that are still not fully identified, Parkinson said.

The study used data from NASA's Nimbus 7 Scanning Multichannel Microwave Radiometer (SMMR) and the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave Imagers (SSMIs) and in the future will be extended with data from the National Space Development Agency of Japan's Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) recently launched on board NASA's Aqua satellite.

Editor's Note: The original news release can be found at http://www.gsfc.nasa.gov/topstory/20020820southseaice.html


Note: This story has been adapted from a news release issued by NASA/Goddard Space Flight Center for journalists and other members of the public. If you wish to quote from any part of this story, please credit NASA/Goddard Space Flight Center as the original source. You may also wish to include the following link in any citation:
http://www.sciencedaily.com/releases/2002/08/020823062734.htm

  Related
stories
Related
discussions
Related
web sites
Related
images
Copyright 1995-2002 ScienceDaily Magazine | Email: editor@sciencedaily.com
Best viewed with Internet Explorer or Netscape Navigator (version 3.0 or higher)




Back to TOP        Back to Warming        Go to FAEC's Spanish Version

You are visitor No.:

since July, 2001

FastCounter by bCentral

If you want to contribute with our work, sending no money,
please click the icons below, Thanks you, very much!


300 MB Hosting, 300 Email Accounts only $7.50/mo.

The Terapin mine stores thousands of your digital photographs easily
without expensive memory cards nor laptop. See how it works here...



Faster MP3 Burning

234x60 Consumer Headset Solution