NSIDC NOTES  -  Issue No. 49 FALL 2004


In this Issue:


Products & Services

AMSR-E Product Updates

Beginning 12 May 2004, NSIDC began distributing the following products with improved algorithms:

Details of the algorithm changes are available. These products are currently being processed with the updated algorithms back to 18 June 2002, the start of the mission.


New Release of AMSR-E Swath-to-Grid Toolkit

An updated version of the AMSR-E Swath-to-Grid Toolkit (AS2GT) is now available from NSIDC. The AS2GT suite of software tools allows users to process swath data into custom grids and provides control over map projection, number of samples per day, input resolution, and interpolation method. Plans for the future are to incorporate any format changes in reprocessed AMSR-E data and to add support for Midori-II AMSR data.

AS2GT is a part of the NSIDC Passive Microwave Swath Data Tools (PMSDT). The current version (0.2) includes a new utility, gsdump, which makes ASCII dumps of generic swath files. Also included are fixes and improvements to the AMSR_E_L2A_togs utility, and improvements to the makefiles, which now automatically install man pages.

For more information and to download the toolkit, see AS2GT: AMSR-E Swath-to-Grid Toolkit.


MODIS Product Updates

A sample of MODIS/Terra Version 3 data from 29 August 2002 through 07 October 2002 (called the "golden month") will be restored for users to correlate between Versions 3 and 4. Users are still encouraged to work with the latest version, or the highest version number.

Processing to MODIS/Terra and MODIS/Aqua Version 5 will begin on 31 May 2005. Notable improvements from Version 4 include the following:


ICESat/GLAS Product Updates

New and improved ICESat/GLAS Release-18 data (GLA01-GLA15) are now available with coverage from 16 October 2003 to 18 November 2003. Notable improvements include better ground height detection in GLA09 and multiple scattering corrections to extinction and optical depth calculations in GLA10 and GLA11.

See Release-18 Products for a summary of changes and known limitations with Release-18, or visit Ordering ICESat/GLAS Products from NSIDC for important disclaimer information and ordering options.

Updated readers are available that run under IDL (6.0 or greater) or the free IDL Virtual Machine (IDLVM), available from Research Systems, Inc.. An updated visualizer is also available that allows users to save plot properties. Access the readers and visualizer at Tools for working with ICESat/GLAS Data.



Cryospheric News

Yet Another Low Year for Arctic Minimum Sea Ice Concentration

For a third consecutive year, the Arctic has seen near-record low sea ice extent in September. This replicates similar patterns seen in 2002 and 2003. There were hints that this might occur as early as May, when anomalously low conditions were first observed. As these conditions persisted throughout summer of 2004, the statistical likelihood of an extreme year increased. While the lagged correlation between ice extent in May and September is modest (0.34), the correlation becomes stronger as the summer progresses to 0.71 between June and September, and 0.84 between July and September.

September 2004 sea ice

Sea ice conditions for September 2004, derived from the Sea Ice Index. Ice concentration anomaly images in lighter grey (the difference in estimated concentration from the mean) and the 1979-2000 median September ice edge (thin line) are combined in the image. The ice edge is well north of its median position off the coasts of Alaska and Siberia. There is a striking lack of sea ice off the east coast of Greenland, a feature noted for the first time in 2002.

These Arctic minima are related to atmospheric circulation via the Arctic Oscillation (AO). When the AO is in a positive phase, atmospheric pressures are lower over the Arctic Ocean, resulting in stronger than normal winds and warm conditions. This fosters both increased ice transport around and out of the Arctic basin as well as enhanced summer melt. A negative phase of the AO yields higher pressure, lighter winds, and colder air temperatures. The AO index has been predominantly positive since the late 1980s, particularly during 1989-1995. A recent study by Ignatius Rigor (University of Washington, Seattle) suggests that this prolonged postive phase fostered transport of much of the thicker multi-year, or perennial, ice pack out of the Arctic. This ice was replaced by thinner first-year ice, leaving the overall Arctic sea ice pack more sensitive to air temperature anomalies than in previous decades. If this theory holds true, then we are seeing an Arctic sea ice pack that is more susceptible than in previous decades to positive anomalies in the AO. In 2002, the low September ice concentration was preceded by a strongly positive winter AO index, while in 2003, the index was weakly positive. In 2004, the winter AO index was strongly negative.

The failure of the sea ice pack to recover supports the hypothesis of a thinner ice pack that is more sensitive to surface air temperature anomalies. While the ice extent minima are occurring annually on a hemispheric basis, these anomalies do not occur in the same geographic location every year. For instance, while the total ice concentration in July 2004 is lower than usual, positive anomalies are seen in Hudson Bay, along parts of the Canadian Archipelago, and in the Laptev Sea, while lower than normal conditions occur in the Kara Sea, north of Svalbard, and along the Beaufort and Chukchi Sea coasts of Alaska. This differs from patterns seen in July 2002 and 2003. These regional anomalies in sea ice concentration are consistent with the spatial patterns of observed anomalies in surface air temperatures.

For further information and sources, please see the Sea Ice Index and the National Climatic Data Center.


Antarctic Glaciers Speed Up in Response to Ice Shelf Collapse

New evidence found by researchers at NSIDC, NASA, and the Instituto Antártico Argentino (IAA) shows that after the Larsen B Ice Shelf disintegrated in 2002, glaciers in the Antarctic Peninsula have both accelerated and thinned en route to the Weddell Sea. The findings indicate that ice shelf breakup may rapidly lead to sea level rise.

In a paper published in Geophysical Research Letters, Ted Scambos and Jennifer Bohlander of NSIDC, Chris Shuman of the Oceans and Ice Branch at NASA's Goddard Space Flight Center, and Pedro Skvarca of the IAA describe two- to six-fold increases in centerline speed of four glaciers feeding the now-collapsed section of the Larsen B Ice Shelf. They also describe elevation losses in three glaciers in the collapse area. The researchers used both Landsat 7 and ICESat satellite imagery in this study.

In the same issue of GRL, Eric Rignot of NASA's Jet Propulsion Laboratory and collaborators describe the same acceleration using Interferometric SAR from RADARSAT. Using their map of the flowspeed, they estimate that the glaciers ought to be thinning by tens of meters. ICESat elevation measurements by the Scambos team corroborate their prediction.

See the news release for more information.


Antarctic Research in the Megadunes

Scientists from NSIDC have spent the last two Antarctic field seasons studying one of the little-known megadune areas of the continent. Ted Scambos, Rob Bauer, and Terry Haran from NSIDC, along with a team of other researchers and support staff, worked in extreme weather conditions to gather data in one of the most remote parts of the world. Unlike snow dunes that are piles of drifted snow, Antarctic megadunes are long, undulating waves in the surface of the ice sheet. The dunes are 2 to 4 meters (6.5 to 13 feet) high, 2 to 5 kilometers (1 to 3 miles) apart.

The team conducted field research collecting snow pit samples, setting up automatic weather stations (AWS), traversing via snowmobile with ground-pentrating radar (GPR) devices, photographing various sites, and drilling shallow and deep ice cores.

Scambos and collaborator Jeff Severinghaus will convene a special session to present science results of the megadunes research at the Fall AGU meeting in December 2004 in San Francisco.

The researchers hope to give the cryospheric research community insight into this unexplored part of the Antarctic ice sheet. Through data analysis they hope to better understand past climate changes, megadune formation, and the annual cycle of wind flow on the surface and within the snow pack.

For more information, see NSIDC's award-winning web site Antarctic Megadunes: research at the edge of the Earth.



Conference News

Tibetan Plateau Meetings

NSIDC staff members traveled to Lhasa and Chengdu, People's Republic of China, 24 July-12 August 2004, to attend a symposium and workshop on the Tibetan Plateau. At the 4th International Symposium on the Tibetan Plateau, 4-7 August in Lhasa, Tingjun Zhang, Siri Jodha Singh Khalsa, Oliver Frauenfeld, and Florence Fetterer presented research including frozen ground on the Tibetan Plateau, AMSR soil moisture data, the validity of the European Centre for Medium-Range Weather Forecasts (ECMWF) temperature analyses and climate change over the Tibetan Plateau, and climate data records available from NSIDC, respectively. Invited plenary talks were presented by Richard Armstrong on a satellite derived snow cover history of the Tibetan Plateau, and by Tingjun Zhang on the permafrost and railroad construction over the Tibetan Plateau.

The Chinese Academy of Sciences (CAS) and The People's Government of Tibet Autonomous Region (TAR) organized and hosted the symposium. NSIDC was one of a number of co-sponsors, including the National Natural Science Foundation of China, (NSFC), China Meteorological Administration (CMA), and the International Arctic Research Center (IARC), Fairbanks, USA.

While in Lhasa, NSIDC staff also visited the Meteorological Bureau, Xizang Autonomous Region, as guests of Director Suo Lang Duo Ji. The site includes a weather station, automated in 2002, with paper archives extending back to 1950. Measurements acquired by the station include surface air and 0.2-3.2 m depth soil temperatures, precipitation, and various radiation measurements. A remote sensing center at the Tibet Atmospheric Environmental Science Research Institute receives and processes NASA EOS and NOAA polar orbiter as well as Chinese FY polar orbiters and geostationary satellite data for applications including snow extent and forest fire monitoring.

Extracurricular outreach activities in Lhasa included Dr. Richard Armstrong's visit to a class at the Kungshon Language School. The school is directed by Lhobsang Pandan, and partially supported through the Boulder-Lhasa Sister City Program.

In Chengdu, NSIDC staff participated in the 10 August Workshop on the Land-Atmosphere Interaction on the Tibetan Plateau, as guests of the Institute of Plateau Meteorology (IPM), China Meteorology Agency. NSIDC research scientist Dr. Tingjun Zhang, who also holds the position of adjunct Director of the IPM, organized the workshop. Presentations and discussions focused on the physical link between surface processes on the Tibetan Plateau with the Asian summer monsoon, and the direction future research, modeling, and data collection should take to better understand these processes. An agreement has been reached that the Data Center at IPM and NSIDC will enhance data exchange in the future.

The contingent from NSIDC received travel support from the IARC, the University of Alaska Fairbanks, USA, and the Institute of Plateau Meteorology, China Meteorological Administration, Chengdu, China.


Workshop on EOS Snow and Ice Products

The First Workshop on Earth Observing System (EOS) Snow and Ice Products will be held at Science Systems and Applications, Inc. (SSAI) in Lanham, Maryland, on 16-17 November 2004. The intent of the workshop is to bring together current and potential users of EOS snow and ice standard products from MODIS, AMSR-E, ICEsat, ETM+, and ASTER sensors. For more information, see Workshop on EOS Snow and Ice Products.


GLIMS Workshop

The Global Land Ice Measurements from Space (GLIMS) project held a one-day workshop in Oslo, in coordination with the International Glaciological Society Symposium on Arctic Glaciers, on 20 August. Representatives from several international Regional Centers discussed progress made on using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imagery to analyze glaciers in their regions (see figure). Glacier data from the GLIMS Regional Centers are being stored in a glacier database at NSIDC that will soon be web accessible.