On Monday, 11 July from 3:00 p.m. through Wednesday, 13 July until 5:00 p.m. (USA Mountain Time), NSIDC data distribution, services, and Web site will be unavailable to accommodate a major upgrade to our data center. We apologize for any inconvenience this may cause you. Need to talk to us? You can always contact our friendly User Services Office at firstname.lastname@example.org or + 1 303.492.6199.
In this Issue
PRODUCTS AND SERVICES
DMSP SSM/I Daily and Monthly Sea Ice Concentration Grids for the Polar Regions are available via ftp through December 1998.
For further information, or to access the data please visit our online data catalog or contact NSIDC User Services.
Dr. Nina Speranskaya of the Russian State Hydrological Institute in St. Petersburg has noted errors in a portion of the Former Soviet Union Hydrological Snow Surveys data set. These errors involve occasional transposition of data between two stations which apparently occurred during the digitization. The majority of these errors seem to be confined to the period 1966-1975, when the format of the analog record books was different from later records. An example of this type of error can be seen in data from the Verkjoyansk station in 1967. This data is actually data from the Srednekolymsk station. These digitization errors affect individual stations on a sporadic basis during this time. Studies of individual stations during this time period may be affected by this error. However, regional scale studies should be affected only slightly.
NSIDC has continued to monitor the Larsen Ice Shelf using AVHRR data. During the past year and a half, the ice shelf has lost roughly 1800 square kilometers. The first scene (on the following page) shows the ice shelf in 1993, before the breakup started. The initial breakup occurred during 1995, seen in the second scene showing a 2000 square kilometer iceberg after it broke off of the Larsen Ice Shelf. Three subsequent AVHRR scenes detail the most recent breakup.
Between March 23, 1998 and November 20, 1998, the shelf lost about 1037.5 square kilometers, and between November 20, 1998 and March 18, 1999 it lost approximately 676.5 square kilometers (scene shown is from February 25, 1999). Images are in either the thermal band (dark areas are warmer) or the visible band.
In the recent scenes, note the difference between the northern and southern half of the calving front. The northern half of the front is curved, with myriad tabular bergs in front of it, very similar to what was seen across the entire front of the Larsen A during breakup in 1995. The southern half is also retreating, but is not «embayed.»
Summertime images of this area consistently show melt ponding present in the northern half of the shelf, and absent in the southern half, so there is an implied link between the extensive surface melting and breakup.
Surface flowstripes on both the Larsen A and Larsen B cross the entire former extent of those shelves, at least in the vicinity of Robertson Island (not visible in the AVHRR scenes - see outlines on December 26, 1993 image). These features are inferred to form at the grounding line and above as part of glacier flow. Using this assumption and the ice flow speed provides an estimate of the minimum age of the shelves; about 400 years, if the flow speed observed has not changed much over time. In other words, it appears that the shelves were stable for centuries prior to the recent events.
Scientists expect no further breakup until the next southern summer (beginning in November), when they will monitor the ice shelf closely.
For more information, see Larsen Ice Shelf Breakup Events.
Professor Roger Barry, CIRES Fellow and Director of the National Snow and Ice Data Center, is one of 37 scientists selected for Fellowship in the American Geophysical Union. This honor is granted to scientists who have attained acknowledged eminence in one or more branches of geophysics. Professor Barry was nominated for "outstanding research, teaching and service in climatology, especially in polar and mountainous regions." The number of Fellows selected annually is limited to no more than 0.1 percent of the AGU membership. There will be a presentation ceremony at the Fall 1999 AGU Meeting.
NSIDC and the Institute for Arctic and Alpine Research (INSTAAR) jointly hosted the 8th Annual Midwest Glaciology Meeting on March 15-16, an informal meeting focused on the climate and dynamics of large ice sheets. About 50 scientists attended. New results on Antarctic ice streams, the central West Antarctic sub-ice geology, and retreat of several Alaskan glaciers were discussed among the 40 talks and 6 posters given. Highlight talks included early SAR interferometric results mapping ice velocities over the Siple Coast (Ian Joughin), SAR mapping of surging in the Bagley ice field (Robert Fatland), early GPS vertical ice motion results for points within the West Antarctic ice sheet (Ian Whillans), tidal modeling of the Weddell Sea to facilitate the use of interferometric SAR over the Ronne Ice Shelf (Doug MacAyeal), and a report on unique firn snow 'megadune' structures in the East Antarctic (Mark Fahnestock).
Richard Armstrong is a co-convener of IAHS Symposium HS2, Interactions Between the Cryosphere, Climate and Greenhouse Gases. He is also presenting two papers in IAMAS JSM41 - The Contribution of Satellite Observations to Global Climate, Ocean and Terrestrial Monitoring. The first paper is an invited keynote paper: Satellite Remote Sensing of Global Snow Cover - A Brief History and the second is with Tingjun Zhang and Jeff Smith, Passive Microwave Sensing of Frozen Soils. Armstrong will also attend the annual Bureau Meeting of the International Commission on Snow and Ice (ICSI) on July 25 in Birmingham.