Using MEMS and Micro-CT to Investigate Micro-scale Temperature Gradients at Stratigraphic Interfaces in Snow

Abstract:

Seasonal snow covers consist of many stratigraphic layers of varying density and thermal conductivity. Weak layers can develop at the interface between these snow layers, potentially reducing stability and increasing the avalanche danger. While it is known that large bulk temperature gradients across a snowpack lead to kinetic snow metamorphism and the development of faceted grains, recent laboratory studies have also identified the local enhancement of temperature gradients near ice-snow interfaces. Here, we present laboratory experiments utilizing a new micro-electrical-mechanical system (MEMS) temperature sensor array, designed for measuring microscale temperature gradients across varying snow slab interfaces. With the aim of further identifying enhanced temperature gradients that may exist at other snow interfaces of varying density and thermal conductivity, we have manufactured snow slab interfaces in the laboratory by using a combination of a benchtop wind tunnel and uniaxial compression. Once created, each snow sample is placed into a 50 mm tall and 20 mm diameter polycarbonate tube and subjected to a 100°C/m temperature gradient for 72 hours. Using the MEMS sensor, in situ temperature measurements are made across the snow slab interface with a spatial resolution of 200 µm and accuracy of 0.5°C to elucidate the microscale temperature gradients. To characterize the rate of kinetic snow metamorphism occurring at the interface compared to the bulk sample, time lapse X-ray computed microtomography (micro-CT) images are also captured every 8 hours. Post-processing of micro-CT images includes calculating the mean and gaussian curvatures, which are then used to identify local.