Snow Modelling Locked Pastures from Rain-on-Snow Events in the Arctic

Rain-on-snow (ROS) events are an increasingly prevalent Arctic extreme weather phenomenon, driven by accelerated atmospheric warming. These events create ice layers within the snowpack, which can prevent foraging for ungulates like reindeers, caribou and muskoxen and have been linked to catastrophic herd die-offs. Accurately simulating physical consequences of ROS, specifically development of these ice crusts, is therefore critical for assessing wildlife habitat suitability. However, the performance of detailed snow models in high-latitude environments remains inadequately evaluated, particularly their ability to replicate the snowpack stratigraphy following complex meteorological events.

This study investigates the capacity of the snow model Crocus-SVS2 to simulate the impacts of known, major ROS events on the snowpack of Banks Island, Nunavut. We focus on a case study where a documented ROS event was followed by a severe muskoxen mortality event in the winter of 2003-2004. Our methodology forces Crocus-SVS2 with three meteorological reanalysis datasets: the Canadian Surface Reanalysis version 2.1 (CaSR2.1) and 3.1 (CaSR3.1), and ERA5 reanalysis. This multi-forcing approach allows to assess not only the model's physical fidelity but also the sensitivity of the simulations to different weather inputs, thereby evaluating the ability of reanalysis products to represent ROS in the Arctic accurately.

Model outputs are analysed to determine if Crocus-SVS2 can successfully replicate the formation, thickness, and vertical position of observed ice lenses within the snow profile. The primary outcome is a robust evaluation of whether an operational snow model, when driven by the best available meteorological data, can serve as a reliable tool for retrospectively analysing ROS impacts in data-sparse Arctic regions. This research also provides a framework to identify key meteorological conditions that separate minor ROS events from those causing catastrophic ungulate die-offs.