HR: 0800h
AN: C21B-1105    [Abstracts]
TI: Antarctic Firn Temperature Measurements from 1949 - 1970: Potential for Climate Trend Determination via Re-measurement
AU: * Muto, A
EM: muto@colorado.edu
AF: National Snow and Ice Data Center, CIRES, University of Colorado, 1540 30th Street, Boulder, CO 80309 United States
AU: Scambos, T A
EM: teds@icehouse.colorado.edu
AF: National Snow and Ice Data Center, CIRES, University of Colorado, 1540 30th Street, Boulder, CO 80309 United States
AU: Bohlander, J
EM: jennb@nsidc.org
AF: National Snow and Ice Data Center, CIRES, University of Colorado, 1540 30th Street, Boulder, CO 80309 United States
AB: Antarctic firn temperature profiles of the seasonal temperature cycle at multiple depths were acquired at several stations in the years surrounding the IGY period. These data may be useful for climate trend determinations if the sites are re-measured. Measurements were made down to 10 - 16 meters, and at time intervals ranging from one day to one month, for most of the annual cycle. In some cases, a record of snowfall is included, permitting corrections for changing depth over time. Data of this type are known to be available for Maudheim(1950), Byrd Station (1957 and 1959), Little America (1957), Wilkes (1958, 1959), South Pole Station (1958), Ellsworth (1958) and Plateau Station (1967); we are currently seeking data for additional sites (e.g. Vostok, Mawson, and additional years for Byrd and South Pole). We present an analysis of the IGY-era data and data gathering methods with the objective of determining data quality. Most of the measurements were made using thermal resistance sensors ('thermohms'), calibrated in ice-water baths and measured to within 0.05 C (equivalent). The large data volume and multiple-depth measurements allow us to use several statistical approaches for assessing the data precision. Data accuracy is inferred by a comparison of data at different depths in the shallow range of measurements. Mean annual air temperature records at the sites will also be compared with the shallow level firn temperature variations. The data were used in the past for several studies of thermal properties of polar snow (e.g. Schytt, 1958, Weller and Schwerdfeger, 1970). We propose to use this same data in conjunction with new, automated measurements, including measurement to greater depths (30 to 60 meters) to determine the multidecadal trend in mean annual temperature. The automated system will include satellite data transmission to obtain temperature records on a near-hourly basis. Modern thermistors installed at an Antarctic Plateau site (Megadunes) demonstrate that hourly mean temperatures can be determined to ~0.02 C, and temperature change rates of 0.001 C/day are detectable in five days. The IGY-era data will be made available in digital form through Antarctic Glaciological Data Center (AGDC) web site (URL:http://nsidc.org/agdc/).
DE: 0726 Ice sheets
DE: 0736 Snow (1827, 1863)
DE: 0768 Thermal regime
DE: 0776 Glaciology (1621, 1827, 1863)
SC: Cryosphere [C]
MN: Fall Meeting 2005