HR: 0800h
AN: C41B-0202    [Abstracts]
TI: A New Look at the Northern Hemisphere Sea Ice Concentration
AU: * Stern, H
EM: harry@apl.washington.edu
AF: Polar Science Center, University of Washington, 1013 NE 40th Street, Seattle, WA 98105 United States
AU: Fowler, C
EM: cfowler@colorado.edu
AF: Colorado Center for Astrodynamics Research, University of Colorado Boulder, 431 UCB ECNT 323, Boulder, CO 80309 United States
AU: Fetterer, F
EM: fetterer@kryos.colorado.edu
AF: CIRES, University of Colorado Boulder, 1540 30th Street, Boulder, CO 80309 United States
AB: It is widely recognized that the Arctic sea ice cover has been shrinking over the past 25 years. Our knowledge of hemispheric sea ice concentration and extent comes almost entirely from satellite passive microwave (PM) data collected since 1978. In this study, we use a new data set of Northern Hemisphere sea ice concentration, derived from weekly operational ice charts spanning more than three decades (1972-2003), to re-examine the regional variability and trends in sea ice area and extent. The ice charts from the U.S. National Ice Center have been converted to EASE-Grid format. Source data for the charts include visible and infrared satellite imagery, active radar imagery, PM data, aerial reconnaissance, ship and shore observations, buoys, model output, information from foreign ice services, and climatology. The PM data are used only when all other forms of data are not available. Thus we have a unique gridded data set that is largely independent of the popular PM products that are widely used by the sea ice community. We divided the Arctic and sub-Arctic seas into regions and created monthly time series of sea ice area and extent for each region. We also obtained the monthly NASA Team sea ice concentration products. We re-gridded these to the same EASE-Grid format as the charts, and computed time series of sea ice area and extent for the same regions. We present comparisons of the regional differences and trends seen in the two data sets. We explain the differences based on the source data used in the charts, and the emissivity of sea ice as detected by the PM instruments. Future work with the ice chart data set includes analysis of multiyear, first-year, and new ice concentrations in order to understand the recent record-low summer ice minima; duration of the ice season, as an indicator of climate change; and analysis of the modes of variability of the ice edge, in order to develop a predictive capability for sea ice extent.
DE: 9315 Arctic region
DE: 4207 Arctic and Antarctic oceanography
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting