Field measurements of sintering after fracture of snowpack weak layers

Abstract

This research documents two cases where field workers unintentionally fractured a snowpack weak layer, but no avalanche released. Measurements from before and after the fractures provide unique data sets on the temporal change of snow stability. Shear strength decreased immediately after fracture on both slopes. Subsequent strengthening occurred in both cases, though the rates differed presumably due to the characteristics of the weak layers. Our results have two important implications. First, they suggest the sub-critical weak layer fractures assumed as a prerequisite in some snow slab avalanche release models are transient features, and future modeling efforts must take this into account. Second, they provide insights into interpreting snow stability tests and assessing the stability of slopes with fractured weak layers.