Determination of the thermal conductivity of sea ice from measurements of ice temperature (and temperature gradients), salinity, ice microstructure and other environmental parameters

The polar oceans' sea ice cover strongly modifies ocean-atmosphere heat transfer. Despite its importance, existing circulation models and large scale sea ice models include overly simplistic parameterizations of the ice thermal conductivity that are likely to contribute to significant errors in estimating ice production rates. A set of field measurements in McMurdo Sound, Antarctica and Barrow, Alaska, were conducted over 5 seasons from which the thermal conductivity of first year sea ice was derived as a function of ice microstructure, temperature (and temperature gradients), salinity and other environmental parameters. Thermistor arrays were deployed in fast sea ice near the Erebus Glacier Tongue to allow measurements of temperature over small volumes with the sensor in direct contact with undisturbed ice grown around it. Data was recorded at 10 min intervals throughout the winter and spring. To estimate thermal conductivity from this data set, an array of dielectric probes were deployed which allow the derivation of the in situ brine volume fraction and bulk ice salinity in the respective ice horizons. In addition, an ice coring programme was conducted to characterise ice properties and heat flow processes over a larger area. Eleven sites were visited with measurements at each including snow and ice characterization and temperature profile measurements. Ice cores were sectioned on site into 5-10cm segments and melted, salinity measurements and sub-sampling for stable-isotope measurements, study of crystal and pore microstructure completed. To extend surface observations, backscatter signatures in Radarsat Synthetic Aperture Radar imagery was analysed. In addition, a set of laboratory based thermal conductivity measurements were made on cores drilled out of large blocks cut from the array sites. Surface and sub-surface first year ice and multi year surface ice were characterised by density and salinity measurements and photographed. The thermal conductivity of the cores was measured in a specifically constructed thermal conductivity measuring apparatus.