In this Issue





Issue no. 32, June 2000


Larsen B Ice Shelf Continues to Retreat: Wilkins and George VI Shelves Stable in 1999-2000 Season

While the gigantic icebergs recently calved from the Ross and Ronne Ice Shelves (the B-15, B-17, and A-43 a, b, and c) have generated a great deal of attention, this activity is unlikely to be a result of recent climate warming in the Antarctic. Both ice fronts prior to the calving were extended unusually far north, and the recent calving merely removed the last 50 to 80 years of ice flow. There is little evidence of rapid warming in either the Ross or Ronne regions, and little indication that either shelf is moving towards a pattern of rapid retreat.

On the other hand, the Larsen and Wilkins have shown extensive retreat in the last two decades, and that pattern is continuing. The Larsen 'B' ice shelf, located on the eastern side of the Antarctic Peninsula, retreated an additional 477 km2 in the past austral summer season. The breakup included a relatively large berg from the southern part of the shelf front of about 135 km2, and further retreat along the northern two thirds of the front in the form of many hundreds of small (10 km2 and smaller) elongate icebergs. Since its maximum recorded extent in early January of 1995, the Larsen 'B' has lost approximately 4715 km2, in a pattern of rapid retreat associated with the presence of melt ponding on the surface during the summer season. Meltwater may decrease the strength of the shelf by enhancing the depth of crevasses or by 'frost heave' as water-filled crevasses refreeze in winter. A recent Landsat 7 image (below) illustrates the melt ponding and fractures in the northern front very well.

The Wilkins Ice Shelf, on the western side of the Peninsula, underwent a dramatic breakup in March of 1998, but the icebergs calved from its northern ice front in that retreat were never swept out. The region has refrozen with fast ice over both of the last two winters, and the shelf is typically surrounded by fast ice for much of the austral summer. As of this writing, there is some evidence of breakup of this seasonal fast ice on the northern front, but the region of mixed small bergs and multiyear fast ice remains intact. The George VI ice shelf also has multiyear ice buffering its current northern margin, and did not retreat further this season.

Melt ponds on the Larsen ice shelf, Antarctica

Meltponds and fractures on the surface of the central Larsen B ice shelf on February 21, 2000 (Landsat 7, NASA; EROS Data Center; processed at NSIDC).


MODIS Products at NSIDC

The Moderate Resolution Imaging Spectroradiometer (MODIS), has been collecting data since February 24, 2000, about 50 days after the launch of the Terra satellite on December 18, 1999. MODIS views the entire Earth surface every one to two days, acquiring 250, 500, and 1000m spatial resolution data in 36 spectral bands. While a few of the MODIS detectors are not operating as expected, and the instrument is undergoing calibration checks, some of the individual channel data (level 1b) have already been used to make some dramatic images, which are available to the public. The NSIDC DAAC MODIS site has a gallery with images that demonstrate the usefulness of MODIS for observing snow and ice.

The MODIS Instrument Science Team is studying the performance of the snow and ice products which are derived from the level 1b data. Meanwhile, NSIDC has been ingesting and archiving the products since early in the year. NSIDC has also been evaluating and testing the user ordering interface (EOS Data Gateway), and preparing data set documentation, in anticipation of the planned product release later this year.

MODIS satellite image of Cumberland Peninsula, Baffin Island, Canada

Sample image from the MODIS gallery, showing snow cover and sea ice (compiled from MODIS bands 1,3, and 4 at Cumberland Peninsula, Baffin Island, Canada).
(February 24, 2000, 16:40 UTC, Pixel size: 500m)

SSM/I File Naming Conventions Revised

To address the Year 2000 issue as part of SSM/I data file naming conventions, NSIDC is revising the file names of two of its standard products to include four digits for the ´year´field.

Beginning with data for January 1, 2000, the file naming convention of the DMSP SSM/I Daily Polar Gridded Brightness Temperatures data and the DMSP SSM/I Daily and Monthly Sea Ice Concentration Grids for the Polar Regions data will change. For the DMSP SSM/I Daily Polar Gridded Brightness Temperatures data, the new file naming convention will be SSMI-F13-gggyyyymmdd.ccc where ggg is the grid (N3A, N3B, S3A, S3B) and ccc is the product channel (19V, 19H, 22V, 37V, 37H, 85V, 85H.). The file names of the daily data from DMSP SSM/I Daily and Monthly Sea Ice Concentration Grids for the Polar Regions will use the convention SSMI-F13-vvvyyyymmdd.THA where vvv is a field reserved for future implementation of algorithm version numbers, T is the ice type (T for Total ice or M for Multi-year ice), H is the hemisphere (N for Northern or S for Southern), and A is the algorithm (B for Bootstrap or N for NASA Team). The new monthly sea ice file naming convention will be SSMI-F13-vvvyyyymm.THA.pp where pp is the cutoff percent.

Please note that until algorithm version numbers are assigned, the ´vvv´ field for both the daily and monthly data will contain three zeros (e.g., ´000´). Contact NSIDC User Services if you have any questions.

GLAS User Survey

NSIDC is conducting a survey to determine the needs and preferences of future users of the Geoscience Laser Altimeter System (GLAS) data. GLAS is a satellite-borne laser ranging and lidar instrument on the ICESat satellite, scheduled to be launched by NASA in July, 2001. This instrument will provide near-global laser surface altimetry, aerosol measurements, and cloud height data. Its primary mission is mapping changes in ice sheet elevation, but it also will determine the scattering properties of the atmosphere and clouds; changes in surface elevation over non-ice surfaces; ocean elevation, roughness, and reflectance; tree canopy height; and land use assessments.

NSIDC's ICESat/GLAS site provides more information about GLAS as well as links to related sites.


If you've visited NSIDC's web site recently, you may have noticed that our URL has changed. NSIDC began using a new URL,, in April, 2000. Although the old URL address will immediately redirect your browsers to the new URL, we recommend changing any links you have made to our web site. Links written as "" can be changed to "".

If you have any questions, please contact NSIDC User Services.


Canadian Snow Data on CD-ROM

A CD-ROM compilation of Canadian daily snow depth and snow course data is being made available to the research community by the Climate Processes and Earth Observation Division of the Meteorological Service of Canada (MSC). The snow depth data consist of daily ruler measurements of snow depth taken by Meteorological Service of Canada observers and archived as daily element 013 in the Canadian National Climate Data Archive. Also included is a substantial number of daily and weekly snow depth observations from paper records that were digitized through a CRYSYS-supported data rescue project. The depth data extend from the late 1800s to mid-1998, although most of the data are in the period after 1950.

The CD-ROM also includes snow course data (depth and snow water equivalent)from snow surveys taken by more than twenty agencies at weekly, biweekly, or monthly frequencies. The data cover the period from the mid-1950s to the mid-1990s, with a pronounced peak in the 1976-1985 decade. It also contains biweekly estimates of SWE derived by interpolating observed snow course density information to MSC snow depth-observing stations.

The CD-ROM is being provided free of charge to universities, research institutions and government agencies for RESEARCH PURPOSES ONLY. Copies of the CD-ROM can be obtained by registering at CRYSYS Free Snow CD-ROM.


Antarctic Glaciological Data Center

The Antarctic Glaciological Data Center (AGDC) at NSIDC provides data management support for NSF´s Antarctic Glaciology Program. The AGDC has developed a web-based archival and distribution system that is being populated with well documented Antarctic glaciological data sets. The AGDC has recently updated its site with improved data registration procedures, a list of current NSF Antarctic Glaciology Program grants, expanded ice velocity and ice shelf monitoring pages, and new pages for the U.S. International Trans Antarctic Science Expedition.


NSIDC welcomes several new employees who joined us this spring, including:

Tom Elliot   (Operations Technician)
Doug Fowler   (EOSDIS IV&V)
Fiona Lo   (Associate Scientist II)
Rick Pitre   SSI&T Engineer)
Laurie Schmidt   (Science Writer III)
Heidi Schumacher   (Operations Technician)
Nick Suszczyk   (Systems Administrator)

NSIDC also bids farewell to the following employees and we wish them well in their future endeavors:

Rachel Hauser  (Scientific Writer), Renea Ericson (Operations Supervisor), and Beth Sigren  (Associate Scientist).

Jason Wolfe, formerly a User Services Representative, is now a Scientific Writer for NSIDC.

For information about employment opportunities at NSIDC, visit Cooperative Institute for Research in Environmental Sciences Professional Positions.


Ice Charting Working Group Meeting Announcement

The second meeting of the International Ice Charting Working Group (IICWG) will be held in Reykjavik, Iceland, October 3-5, 2000. The conference will provide a forum for discussion of sea ice chart production and distribution. IICWG promotes cooperation between the world's ice centers on all matters concerning sea ice and icebergs. For more information, see the IICWG web page or contact Dr. Thor Edward Jakobsson, Icelandic Meteorological Office (


The 2000 International Geoscience and Remote Sensing Symposium (IGARSS), "The Role of Remote Sensing in Managing the Global Environment," will be held on July 24-28 in Honolulu, Hawaii. NSIDC attendees include Richard Armstrong, Tracy Thrasher Hybl, Ted Scambos, Greg Scharfen, Annette Varani, and Tingjun Zhang. Look for their posters and presentations at the meeting.