Front Page, Spring 2006

Antarctica is Shrinking
Gravity survey shows overall loss in ice.

Jacqueline Ruttimann, news@nature.com [Naturenews@info.nature.com]

"In my mind, there is no doubt that Antarctica is losing mass," said Isabella Velicogna of the University of Colorado at Boulder, and lead author of a paper published in Science 1, the latest study in an avalanche of research on the topic.
Just two weeks ago, Science also published an article stating that Greenland is melting more quickly than it is growing (see 'Glacial pace picks up').
Previous work on both of these areas has shown that the edges of the ice sheets are melting while their centres are growing thanks to increased snowfall. It has been unclear until recently whether the sum of these two effects is a growing or shrinking mass of ice.

The big melt

Antarctica is twice as large as Australia and harbours 90% of Earth's ice. It is divided by the Transantarctic Mountain Range into two main ice sheets: the West Antarctic ice sheet, a large peninsula that stretches from the South Pole towards the southern tip of South America , and the East Antarctic ice sheet that forms the rest of the continent.
There is evidence that West Antarctica is melting. Two sections of the Larsen ice shelf, in the West Antarctic ice sheet, broke apart in 1995 and 2002, which has sped up the melting of glaciers that were behind it.
Whereas the melting of floating ice shelves does not add to sea-level rise, the melting of the sheets behind it does. Researchers from the British Antarctic Survey in South Georgia say that if the entire West Antarctic sheet melts it would catastrophically raise global sea levels by more than six metres. But the East Antarctic ice sheet is thought to be getting bigger thanks to increased snowfall, which could offset the melting.
To get the full picture, Velicogna and her colleagues used a special pair of NASA satellites known as the Gravity Recovery and Climate Experiment (GRACE). These orbit in tandem several hundred metres from Earth and provide monthly estimates of Earth's global gravity field and mass distribution. If the lead satellite passes over a structure with a large mass that causes it to speed up, this pulls it away from the trailing satellite. So the changing distance between the two satellites helps to determine the mass of underlying objects.
By looking at data from Antarctica from April 2002 to August 2005, Velicogna calculates that Antarctica is losing something between 72 and 232 cubic kilometres of ice per year. This is equivalent to an annual rise in the ocean of 0.4 millimetres.

Mass confusion

The main reason for the relatively large uncertainty in how much ice is being lost is that with GRACE data it is hard to distinguish a change in mass due to extra snowfall from a change in mass due to shifts in the crust beneath, says Velicogna.
The Antarctic is moving slowly upwards as it rebounds from the melting of glaciers that lay above it during the last ice age. As it shifts, the mass of the Earth's crust is redistributed. This has to be modelled and removed from the equation before the GRACE data can be used to show changes in ice mass.
"They're getting the important answer that Antarctica is losing ice mass," says Jay Zwally, a glaciologist from the Goddard Space Flight Center in Greenbelt , Maryland . "But the numbers need more work done on them."

Experienced Secondary Science Teachers Needed!! Applications will be accepted through May 26 th or until filled. Join COLORADO 's Online Science Mentoring Program:  
e-Mentoring for Student Success, eMSS.
Coordinated by the University of Northern Colorado
·         Mentor a beginning science teacher in your state and content area
·         Conduct weekly online activities with your mentee
·         Receive a $1400* ( * This includes an online summer institute stipend ) for August 2006 - June 2007 participation
·         Help implement an innovative national science mentoring program, and more.
·         The Mentors are encouraged to attend Colorado 's eMSS Fall Meeting at the Colorado Science Convention on Friday, November 17, 2006 in Denver . This meeting will allow participants to meet each other, address questions and concerns on eMSS in Colorado , and review Convention offerings that support science teaching and learning at the secondary school level.
For further information, contact Lori Reinsvold lori.reinsvold@unco.edu

e-Mentoring for Student Success (eMSS) is currently recruiting experienced (5+ years middle and high school) science teachers to participate in an innovative online mentoring project. Mentors will work online with beginning science teachers, research scientists and other mentors. Retired teachers are encouraged to apply. eMSS is a Partnership with the National Science Teachers Association,
New Teacher Center @ UCSC, and Montana State University
For Online Application visit: emss.nsta.org
The application can be found by selecting the Colorado link

Or Contact
Lori Reinsvold, 970-351-1280 or lori.reinsvold@unco.edu
Teresa Higgins, 970-351-2617 or teresa.higgins@unco.edu