HR: 08:30h
AN: C51C-03    [Abstracts]
TI: Role of Heat Flux Through Snow in Antarctic Sea Ice Growth
AU: * Maksym, T
EM: maksym@usna.edu
AF: Department of Oceanography, United States Naval Academy, Annapolis, MD 21402 United States
AU: Jeffries, M O
EM: martin.jeffries@gi.alaska.edu
AF: Geophysical Institute, University of Alaska Fairbanks 903 Koyukuk Dr, Fairbanks, AK 99775-7320 United States
AU: Watts, M N
EM: mnwatts@mit.edu
AF: Department of Ocean Engineering, Massachusetts Institute of Technology 77 Massachusetts Ave, Cambridge, MA 02139 United States
AB: The heat flux through snow on Antarctic sea ice was calculated to examine its role in controlling sea ice thickness and ice types. A statistical determination of the heat flow through the snow was calculated using over four thousand point temperature measurements of snow and sea ice from four cruises in the Ross, Amundsen, and Bellingshausen Seas. Calculated heat flux through the ice was used to determine an effective thermal conductivity for the snow. Two approaches were taken: (1) calculation base on the temperature profiles at individual snow pit and ice core sites, and (2) calculation based on point temperature measurements across ice floes. The effective thermal conductivity determined from the first method was 0.29 W m$^{-1}$ K$^{-1}$, and the second method was 0.30 W m$^{-1}$ K$^{-1}$, in close agreement with values typically used in large-scale sea ice models, but approximately twice the measured values for the same cruises. There was also significant variation between cruises, indicating a possible dependence on snow properties that is not captured by the simple snow parameterizations used in current large-scale sea-ice models. Analysis shows some dependence of effective thermal conductivity on snow depth. This may result from snow property variations but may also indicate a variation in heat flow mechanisms that depend on the heterogeneity of the snow cover. Unlike at the SHEBA site in the Arctic, the analysis showed no evidence for enhanced heat flow through ridges. We suggest that the discrepancy between measured and effective thermal conductivity may be due to the presence of icy layers within the snow cover, and brine at the base of the snow, both of which can enhance the heat flow. As these properties are controlled by environmental factors, significant variability in vertical heat transfer can result, as evidenced by the variability among cruises. This suggests that to accurately predict the response of Antarctic sea ice to environmental change may require more sophisticated treatment of processes within the snow cover. Finally, using a sophisticated one-dimensional thermodynamic model of sea ice, we investigate how variations in these snow processes affect the thickness of the underlying sea ice and snow ice production.
DE: 4540 Ice mechanics and air/sea/ice exchange processes
DE: 1863 Snow and ice (1827)
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting