HR: 0800h
AN: C11A-0088    [Abstracts]
TI: Interpretation of the Shallow Firn Layer Temperature Data from GC-Net AWS Stations
AU: * Sampson, K M
EM: Kevin.Sampson@colorado.edu
AF: Cooperative Institute for Research in Environmental Sciences, CIRES Building Room 318 Main Campus University of Colorado, Boulder, Boulder, CO 80309,
AU: Steffen, K
EM: Konrad.Steffen@colorado.edu
AF: Cooperative Institute for Research in Environmental Sciences, CIRES Building Room 318 Main Campus University of Colorado, Boulder, Boulder, CO 80309,
AB: Measurements of temperature and other climate variables for the Greenland ice sheet are continuously recorded by the Greenland Climate Network (GC-Net) surface meteorological stations. All GC-Net stations are equipped with a string of thermocouple temperature sensors to provide a record of the firn temperature profile as well as surface temperature and snow height change (dH/dt) sensors. Thermocouple temperature measurements are accurate to 0.1C. A subset of six automatic weather stations is chosen that exhibits good spatial and temporal coverage of the extensive, high elevation (>2000m) accumulation regions of the interior of the ice sheet. The procedure to remove simultaneous temperature variations (STVs) in the thermocouples follows a newly developed, physically based data cleaning technique. This method allows more physical process and parameter information to be extracted from the existing firn temperature data. To account for densification in the firn, and thus movement of the sensors relative to one another, a temperature-dependent model of firn densification is used which reproduces the strong seasonal signal in the densification rate of the upper firn. Harmonic trend analysis reveals the cycle of sub-surface temperatures, as well as a significant upward trend in all study sites after the year 2000. The firn temperature increase observed at various depths in the firn reveals an air temperature increase that is masked by the large seasonal and inter-annual variability in the record. The temperature increase experienced at 10m depth is as great as .3C/year. Further, the in situ time series of constant-depth temperatures at various levels are compared with modeled temperatures to validate the use of GC-Net data to estimate heat transfer into the snowpack. Finally, a new set of firn-temperature distribution maps is presented.
DE: 0700 CRYOSPHERE (4540)
DE: 0726 Ice sheets
DE: 0736 Snow (1827, 1863)
DE: 0768 Thermal regime
SC: Cryosphere [C]
MN: 2007 Fall Meeting