Title: Measuring the Thermal Conductivity of Sea Ice

Speaker: Daniel Pringle (Geophysical Institute, University Alaska, 
Fairbanks)

Sea ice is a dynamic component in the Earth climate system, forming a 
seasonally-variable thermal and mechanical barrier between ocean and 
atmosphere, and through a variety of feedback mechanisms sea ice acts as 
both an agent and indicator of climate change. One important parameter for 
modeling these complex interactions is the effective-medium thermal 
conductivity, k_si, which controls the conductive heat flux through the 
ice, and the thermodynamic response of the ice to changes in forcing.  

Sea ice is a composite material with temperature-dependent pure ice, 
brine, air, and salt precipitate fractions, and its microstructure and ice 
floe scale variations complicate the measurement  and prediction of 
transport properties. Until recently k_si remained poorly measured, and 
most sea ice models have used a semi-empirical parameterization that 
predated virtually all experimental values, and most theoretical 
predictions. There is also as expectation of a convective enhancement to 
the heat flow near the bottom ice water interface, but this has proved 
elusive to measure.

I will report results from a recently completed program to measure k_si 
from in situ "thermal diffusivity" measurements in Antarctica and Alaska, 
and from a direct "bench top" experiment, and discuss their departure from 
the existing parameterization. I will summarize previous experimental 
results with respect to their reliability and applicability for comparison 
with recent theoretical predictions (Ken Golden et al.).