In this Issue



Issue 30, Winter 1999


We have experienced a temporary disruption in our printing schedule for NSIDC Notes, and apologize for any inconvenience. We will resume our quarterly schedule in 2000 and you should receive your next issue of Notes in the spring.

Over the next few months, we will redesign Notes to incorporate several suggestions from our NSIDC Notes survey taken last summer. We appreciate your input and look forward to better serving your cryospheric and data information needs in the future.


U.S. National Reconnaissance Imagery of the SHEBA Site

Recognizing the sensitivity of the polar regions to small changes in climate, the National Science Foundation (NSF) and the Office of Naval Research funded the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment to examine the Arctic Ocean's energy budget. The experiment's operation base was a Canadian ice breaker frozen into the polar pack ice for one year. Approximately 50 scientists made over 300 types of observations with the expectation of improving global climate forecasting.

On August 3, 1999 Vice President Gore announced the release of 59 previously classified images of the SHEBA site. "No place on Earth is more sensitive to global warming than the Arctic, and these satellite images provide scientists with valuable data for understanding how climate change affects this complex region," the Vice President said. "By making these satellite images available to the scientific community, we take another important step toward meeting the challenge of global warming."

Norbert Untersteiner, professor emeritus at the University of Washington, and Florence Fetterer at the National Snow and Ice Data Center in Boulder, Colorado, had used high-resolution reconnaissance imagery when conducting summer sea ice studies from 1993 through 1995. They and the Medea Polar Panel that sponsored their sea ice research realized that the SHEBA project would greatly benefit from acquiring similar data.

"The one-meter reconnaissance imagery seemed an obvious choice because it allows researchers a means of examining pack ice features close-up. The imagery also provides a wider view of the ice area around the ship that can be correlated to low-resolution civilian satellite imagery," said Fetterer. The task was aided by the multi-agency Civil Applications Committee, which in 1998 created a means for federal agencies to procure classified remote sensing data if they could show that their data requirements could not be fulfilled by another, conventional data source.

At the request of NSF, the National Imagery and Mapping Agency officially approved declassification of 59 images. For an example of the U.S. National Reconnaissance Imagery of the SHEBA Site see, our data catalog.

The data will be distributed by NSIDC and the EROS Data Center. If you would like to be notified when the data are available, visit the URL above and follow the link, NSIDC User Services.

Near Real-Time Sea Ice Concentrations and Brightness Temperatures

NSIDC recently released near real-time sea ice concentrations and brightness temperatures (TBs) to provide researchers with timely sea ice information during periods of polar melt onset and freeze-up. Marshall Space Flight Center provides NSIDC with daily TBs derived from the Defense Meteorological Satellite Program-F13 (DMSP) Special Sensor Microwave/Imager (SSM/I) for both the Northern and Southern Hemispheres. The TBs are gridded onto the SSM/I polar stereographic grid. Sea ice concentrations are generated from the brightness temperatures using the NASA Team algorithm.

The near real-time data will be retained on the ftp site until NSIDC's standard sea ice product, the DMSP SSM/I Daily and Monthly Sea Ice Concentration Grids for the Polar Regions, becomes available. Typically these data are available three to six months after the initial satellite overpass. Near real-time data will remain online and available to users for three months after receipt of NSIDC's standard products.

Possible differences between the standard and near real-time products remain to be determined. The near real-time data do not supplant the standard products, but instead fill the time gap between present-day and the delivery of the Remote Sensing Systems (RSS) data. Users are therefore cautioned to be aware of potential data differences, and should continue using the standard products derived for time series analyses.

For more information about these data, please contact NSIDC User Services or see our data catalog.

Polar Ice Sheet DEMs and Elevation Data at NSIDC

NSIDC has created a central web site designed to bring together information about our digital elevation model (DEM) data products for Greenland and Antarctica. Polar Ice Sheet DEMS and Elevation Data is located at: DEMS

A summary page provides a brief overview of each of our current data sets, including coverage, data source, media (ftp or CD-ROM), grid scale resolution, ellipsoid, geoid, investigator names, and links to data access and documentation. Future data sets will be added to this summary page as they become available. The summary page serves as an information resource, to compare and contrast the different data products.

In addition to links to other altimetry and DEM resources, the site also includes a contact form for investigators who wish to contribute their DEM data to the NSIDC collection.

We hope this new web page will benefit investigators and users by making information about our altimetry and elevation data products more concise and readily available, particularly for researchers who work regularly with ice sheet topographic data.

SSM/I Polar Stereographic Grid Error Notice

NSIDC has been alerted that the latitude, longitude, and pixel area files supplied with the SSM/I polar stereographic grid data contain errors. These errors affect the latitude, longitude and pixel area files supplied with the DMSP SSM/I Daily Polar Gridded Brightness Temperatures and the DMSP SSM/I Daily and Monthly Sea Ice Concentration Grids for the Polar Regions, as well as the latitude and longitude files supplied with the Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I Passive Microwave Data.

For the DMSP SSM/I Daily Polar Gridded Brightness Temperatures and the DMSP SSM/I Daily and Monthly Sea Ice Concentration Grids for the Polar Regions, the errors affect the files for the Northern Hemisphere located on:
and on the brightness temperature CD-ROMs. Specifically, the errors affect the following three files:

psn25area.dat pixlarea.n
pan25lats.dat latitude.n
pan25ons.dat longtude.n

The location files from the DMSP SSM/I Daily Polar Gridded Brightness Temperatures and DMSP SSM/I Daily and Monthly Sea Ice Concentration Grids for the Polar Regions were found to be in error by up to 8 km and the area file was in error up to 0.5 sq. km.

On June 22, 1999, the files that were found to be in error were replaced on NSIDC's ftp site by correct files and registered users were notified. Users of this data should download the new latitude, longitude, and pixel area files from: TOOLKIT/GEO_COORD

For the Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I Passive Microwave Data, produced by Goddard Space Flight Center (GSFC), the latitude and longitude files contain errors for both the Northern and Southern Hemispheres. These errors affect the files located on the CD-ROMs, specifically the following four files located in the Tools directory:


The location files for the Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I Passive Microwave Data were found to be in error by 27.7 to 36.3 km.

Corrected latitude and longitude files were staged to NSIDC's ftp site on June 25, 1999. Users of this data should download the new latitude and longitude files for both hemispheres from: TOOLKIT/GEO_COORD

Note: Users should be aware that the NSIDC and GSFC pixel-area grids differ slightly (by no more than 1%) due to use of different procedures to calculate areas.

Please contact NSIDC User Services if you have any questions.

Arctic Ocean Snow and Meteorological Observations from Drifting Stations Error Notice

Users of the Arctic Ocean Snow and Meteorological Observations from Drifting Stations data on CD-ROM were recently notified of data errors found on the CD- ROM. A revised version of this data set with corrections and newly available data will be released as soon as current quality control efforts are completed.

Contact NSIDC User Services if you have questions, or if you are using these data and did not receive a notice via postal mail.


IUGG, July 1999

NSIDC's Ted Scambos attended the recent International Union of Geodesy and Geophysics (IUGG) meeting July 22 and 23, and a meeting on mapping the Antarctic bedrock surface at British Antarctic Survey in Cambridge, UK, on the 24th and 25th.

The BEDMAP (Antarctic bedrock mapping project) meeting was an organizational meeting to discuss data sources and coordination among data centers contributing to the effort. A consortium of researchers and data centers are attempting to compile all existing information on the shape of Antarctica beneath its ice cover. NSIDC's Antarctic Glaciological Data Center is a participating member of the BEDMAP consortium.

Fall AGU Meeting, San Francisco, 13 - 17 December 1999

NSIDC will again have an exhibit booth at the Fall Meeting of the American Geophysical Union.We look forward to the opportunity to discuss our products and services with you. See you there!

30th International Arctic Workshop

The 30th International Arctic Workshop will be held on Thursday through Saturday, March 16-18, 2000 at the Institute of Arctic and Alpine Research, University of Colorado, Boulder, Colorado, U.S.A.

The meeting will consist of oral and poster presentations covering all aspects of high-latitude environments, past and present. Visit INSTAAR's web site for information on registration, program, abstract submission, and student support.



NSIDC bids farewell to three employees whose contributions to the data center and hard work will be missed. Jennifer Bohlander, who worked with Ted Scambos processing Antarctic ice stream imagery; Matt Cross, who served as the ARCSS Data Manager; and Chris Haggerty, who worked closely with Florence Fetterer collaborating on NOAA data sets. We wish them the best of luck in their new endeavors.

For employment opportunities at NSIDC, visit the CIRES web site.