Thermal conductivity and heat transfer through the snow on the ice of the Beaufort Sea

Abstract

Eighty-nine point measurements of the thermal conductivity (ks) of the snow on the sea ice of the Beaufort Sea were made using a heated needle probe. Average values ranged from 0.078 W m-1 K-1 for new snow to 0.290 W m-1 K-1 for an ubiquitous wind slab. ks increased with increasing density, consistent with published equations, but could also be reliably estimated from the metamorphic state of the snow. Using measured values of ks and snow stratigraphy, the average bulk value for the full snowpack was 0.14 W m-1 K-1. In contrast, ks inferred from ice growth and temperature gradients in the snow was 0.33 W m-1 K-1. The mismatch arises in part because the second estimate is based on measurements from an aggregate scale that includes enhanced heat flow due to two- and three-dimensional snow and ice geometry. A finite element model suggests that the complex geometry produces areas of concentrated heat loss at the snow surface. These "hot spots," however, increase the apparent conductivity only by a factor of 1.4, not enough to fully explain the mismatch. Nonconductive heat transfer mechanisms, like natural and forced air convection, may also be operating in the snowpack, though the ubiquitous presence of low permeability wind slabs potentially limits their effectiveness. The relative contributions of effects due to snow and ice geometric and nonconductive processes within the snowpack remain uncertain.