Thermal Conductivity of Polar Firn

The vast Greenland and Antarctic Ice Sheets are covered by many tens of meters of polar firn, which is snow that is years to centuries old. Both ice sheet modeling and decoding satellite data require knowledge of the thermal conductivity of polar firn with depth, yet direct measurements are not available. The first direct measurements of the variation of the effective thermal conductivity of polar firn with depth are presented. A custom device has been designed and constructed, and validation of the device using materials of known thermal conductivity is presented. Using the validated device, measurements were made on firn core samples spanning depths from 4 to 47 m from an undisturbed site near the South Pole, Antarctica. Results show that the thermal conductivity of polar firn increases with depth, with values ranging from 0.617 to 1.018 W/(mK). The associated thermal diffusivities range from 20.95 to 25.68 m2/a. Correlations of the thermal conductivity with other material properties are discussed.