In this Issue

NSIDC ON THE WEB
BREAKUP OF THE LARSEN B ICE SHELF MAY BE UNDERWAY
NSIDC IN THE NEWS
ARCTIC SYSTEM SCIENCE (ARCSS)
PRODUCTS AND SERVICES
NEWS FROM OTHER CENTERS
PERSONNEL

NSIDC Notes

Issue 25, June 1998

NSIDC ON THE WEB

West Antarctic Ice Velocity Data

Ice velocity data from the ice streams and perimeter glaciers of West Antarctica will be available soon. The data consist of over 100,000 vectors from the Siple Coast area, covering parts of Ice Stream B, catchment areas of C, Siple Dome, and large portions of Ice Streams D, E, and F, the Prestrud Inlet and Sulzberger Bay. The majority of the data comes from semi-automated feature tracking using pairs of Landsat and SPOT images, a method discussed in Scambos et al., 1992. Other data sets are derived from GPS (Global Positioning System) and TRANSIT satellite ice motion surveys. The data to be included initially in the web site have come from recent work by Ted Scambos funded by NASA and NSF research grants, and from publications by Whillans et al., 1993 and Bindschadler et al., 1995.

The web site will contain an overview satellite image of West Antarctica showing the general location of the data sets, and image maps showing speed contours and the location of the data points for the individual study areas. The data will be transferable directly from the web site in tabular form, with each table containing latitude, longitude, speed, bearing, and estimated errors for speed and bearing. A short text section will accompany the data tables, describing the specific images or other sources the data was derived from, pertinent references, and estimated location accuracy.

sample ice velocity image

We would like to solicit the glaciological community for similar data sets for anywhere in the Antarctic ice sheet, to eventually create a compendium of ice motion data. The data should be well-characterized, with good estimates of location and accuracy. A paragraph describing the data collection technique would also be required. We are particularly interested in older data that may soon be lost or forgotten; such data is extremely valuable for change detection.

The initial data sets will be available after July 1, 1998. For further information, please contact NSIDC User Services.

Scambos, T. A., Dutkiewitcz, M. J., Wilson, J. C., and Bindschadler, R. A., 1992. Application of image cross-correlation software to the measurement of glacier velocity using satellite image data, Remote Sensing of Environment 42:177-86.

Bindschadler, R. A., Vornberger, P. L., Blankenship, D. D., Scambos, T. A., and Jacobel, R. W., 1995. Surface velocity and mass balance of Ice Streams D and E, West Antarctica. Journal of Glaciology 42(142):461-75.

Whillans, I. M., Van der Veen, C. J., 1993. New and improved determinations of velocity of Ice Streams B and C, West Antarctica. Journal of Glaciology 39(133): 483-90.

BREAKUP OF THE LARSEN B ICE SHELF MAY BE UNDERWAY

In March 1998, NSIDC posted an article on the breakup of the Larsen B Ice Shelf, and subsequently issued a press release that generated a flurry of publicity. News agencies from the United States and Europe contacted Dr. Scambos for interviews and information, including the Associated Press, CNN, National Public Radio, ABC/Discover, the British Broadcasting Company, U.S. News and World Report, Time Magazine, Science News, and several other national and international newspapers.

According to recent satellite imagery, the Larsen B Ice Shelf appears to have begun the process of breakup, receding past its historical minimum extent, and past the point where recent modeling suggests it can maintain a stable ice front. The breakup appears closely associated with the areas over which melt ponding is observed during warmer summer seasons.

Two AVHRR thermal-channel images of the Larsen B area from the NSIDC's AVHRR Polar 1 km Level 1b Data Set are shown. The first image, from February 15 of this year, shows melt ponding typical at this time of year in warm summers. The ice front in this image represents the approximate appearance of the ice shelf since the events of early 1995, when a large iceberg calved off the margin of the ice shelf, and when the Larsen A ice shelf, formerly to the north of Robertson Island, disintegrated. Up until February 15, only minor modifications to the ice front had been observed.

The second image, from March 23, clearly shows the new embayment, and indicates a loss of ~200 square kilometers of ice shelf. The front has retreated by ~5 km along the northern 40 km of ice front.

15 February 1998 showing melt ponding typical at this time of year in warm summers
23 March 1998 image showing new embayment, indicating loss of ~200 square kilometers of ice shelf

The new embayment is occurring along the seaward edge of the part of the ice shelf where melt ponding is most commonly observed. Monitoring of the Larsen ice shelves over the last few years has shown that melt ponding regularly occurs north of Cape Disappointment, but ponding to the south is seen much less frequently. Melt ponds were also observed over the entire Larsen A ice shelf prior to its breakup, and are observed on the Wilkins and George VI ice shelves, both of which are suspected of currently undergoing slower irreversible retreats.

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With this breakup, the shelf has retreated past its previous limit. If the recent modeling scenario is correct, the retreat will continue in the next season, perhaps rapidly if storms and sea ice conditions are appropriate. At present, the onset of the winter season, with sea ice extent increasing, probably precludes much additional evolution. Sea ice shields the shelf from wave action, which may be important for facilitating breakup.

NSIDC regularly monitors the ice shelves of the Peninsula and West Antarctica, using data from EROS Data Center's Global Land 1km AVHRR Data Set, and from the Colorado Center for Astrodynamics Research's DOMSAT receiver. The archive of AVHRR scenes of the ice shelves is collected and maintained by Jennifer Bohlander.

For more information please contact NSIDC User Services.

NSIDC IN THE NEWS

NSIDC's Web Site in Discover Magazine

NSIDC's Glacier pages were cited in a recent issue of Discover magazine (See Discover, June 1998, 19(6), p. 31) as being among the best science destinations on the World Wide Web.

ARCTIC SYSTEM SCIENCE (ARCSS)

Greenland Summit Ice Cores CD-ROM is Now Available

The data from the Greenland Summit Ice Cores are now available on CD-ROM. The ice core records from the U.S. Greenland Ice Sheet Project Two and the European Greenland Ice Core Project represent a comprehensive data set containing some of the highest resolution paleoclimate data ever obtained.

Accompanying the data are full descriptions of the GRIP and GISP2 projects, a search engine for authors and data, and a simple and easy to use tool for analyzing the ice core data.

Compilation of these data was a collaborative data management effort involving a multi-institutional team from the National Snow and Ice Data Center at the University of Colorado, the World Data Center for Paleoclimatology at the National Geophysical Data Center , and the International Ice Core Data Cooperative at the University of Colorado. Special thanks go to Mark Twickler (GISP2 Science Management Office) and Eric Wolff (representing the GRIP ice core community) for all of their time, effort and support.

Data from the GRIP and GISP2 core can also be accessed at ARCSS, the NOAA Paleoclimatology Program at the National Geophysical Data Center, and the NOAA Paleoclimatology Program Medias-France site. For further information or to request a copy of the CD-ROM, please contact NSIDC User Services.

PRODUCTS AND SERVICES

New Data Set Available from NSIDC

Circumpolar Active-Layer Permafrost System (CAPS)

The National Snow and Ice Data Center in cooperation with the International Permafrost Association (IPA) and its Working Group on Data and Information will release a CD-ROM at the Seventh International Conference on Permafrost, June 1998, in Yellowknife, N.W.T., Canada. Titled Circumpolar Active-Layer Permafrost System (CAPS), the CD-ROM is intended for a broad audience including the scientific and engineering communities, educators and policy makers. Contents include:

The IPA, an affiliated organization of the International Union of Geological Sciences, and its eight working groups provide information products related to permafrost, seasonal frost, artificial ground freezing, and periglacial phenomena. The Working Group on Data and Information developed the Global Geocryological Database (GGD), a collection of metadata on permafrost data collections from around the world.

The CAPS CD-ROM was produced at NSIDC with funding from NOAA's Environmental Services Data and Information Management project. Additional funding for the development of CAPS and the GGD was provided by the IPA; NSF; the Geodata Institute at the University of Southhampton, UK; and the Cooperative Institute for Research in Environmental Sciences (CIRES).

For further information or to request a copy of the CD-ROM, please contact NSIDC User Services.

Former Soviet Union Monthly Precipitation Archive, 1891-1993

This archive, compiled by P. Groisman of the University of Massachusetts, consists of monthly totals of precipitation measurements from 622 stations in the Former Soviet Union. Corrections have been made to account for variations resulting from the use of different rain gauges, and for winds and wetting losses. The data, in ASCII format, are available via ftp.

For more information please contact NSIDC User Services.

NEWS FROM OTHER CENTERS

Permafrost and Climate in Europe (PACE)

PACE is a three-year project that will establish a network of long-term ground temperature monitoring stations in mountain permafrost across Europe, develop new methods of mapping and modeling permafrost distribution, and formulate new process based mountain slope hazard assessment methodologies.

Mountain permafrost provides a sensitive indicator of climate warning because, in contrast to non-permafrost areas, lateral groundwater migration cannot occur through frozen ground, so that ground temperatures are largely controlled by conducive heat transfer from the atmosphere. Since short-term atmospheric temperature fluctuations are rapidly attenuated with depth in permafrost, longer-term climatic cycles may be analyzed by monitoring perturbations in the geothermal gradient in deep (80-100 meter) boreholes.

Most General Circulation Models predict a latitudinal gradient in climatic response to atmospheric warming, with more rapid changes at higher latitudes. Therefore the PACE Project will establish a transect of monitored boreholes from Svalbard (Spitzbergen, Norway) in the north, to the Sierra Nevada (Spain) in the south, including intermediate sites in Sweden, Norway, Switzerland, and Italy. An additional site in Germany is also planned, funded externally from the PACE project. At each borehole, ground temperatures will be monitored to a depth of at least 80 meters and data will be archived via the International Permafrost Association's Global Geocryological Database.

Further information about the PACE Project may be obtained from Dr. Charles Harris, Department of Earth Sciences, Cardiff University, P.O. Box 914, Cardiff CF1 3YE, United Kingdom, or by visiting PACE.

PERSONNEL

Farewell to Ann Brennan

Ann retired from her position as Head of Information Services at the end of May. In 1978, she joined the fledgling NSIDC after WDC for Glaciology was transferred to the University of Colorado from Tacoma, Washington. She oversaw and acted as Technical Editor for Glaciological Data Reports 7-29, edited many journal papers and publications, and compiled NSIDC Notes and weekly reports to NOAA. Ann also contributed to the Polar Bibliography Working Group and the Polar Libraries Colloquy. During her career at WDC/NSIDC the library evolved from card catalogue to a computerized catalogue system for almost 40,000 items. A 20-year cumulative bibliography of permafrost literature she assembled is on the new CAPS CD-ROM (see p. 3).

We wish Ann well in her retirement and in her continuing role as a docent at the Denver Art Museum.