Seasonal snowpack quality and hazardous event detection in Dall Sheep habitat; modelling and remote sensing approaches to examine long-term patterns of variability.

Christopher Cosgrove, Oregon State University, cosgrovc@oregonstate.edu (Presenter)
Anne Nolin, Oregon State University, nolina@science.oregonstate.edu

Dall sheep are an emblematic species of alpine northwestern N. America and a large ungulate, reliant on year-round access to forage in open-alpine terrain. Their population decline, 20% range-wide since 1990, may be a description of broad-scale alpine ecosystem change in Alaska and northwestern Canada, with changing seasonal snow cover thought to be a principal cause. For a study area in the north Wrangell St Elias National Park, a physically based, spatially explicit snow evolution model (SnowModel) is forced by surface level meteorological data from the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) product. Producing a time series of high resolution (30 m, daily) snow and metrological variables (e.g. snow depth, total precipitation) from 1980 to 2017, metrics potentially important to Dall Sheep movement and forage (e.g. percentage area under a threshold snow depth) are examined for long term trends and patterns of temporal and spatial variability. September to November snowfall is shown to have greater volume and year-on-year variability than later winter months where snowfall is limited. This suggests that the volume of snowfall in these months is critical for determining the available area accessible for Dall Sheep forage during the entirety of the snow season. Total days per month with rain-on-snow (RoS) is shown to be slightly increasing in the month of September from the model data, these events potentially cause forage-inhibiting, season-lasting ice layers within the snowpack. Following this, a methodology using the National Aeronautics and Space Administration’s (NASA) Calibrated Enhanced Resolution Passive Microwave Brightness Temperature (CETB) product is presented for detecting RoS events at spatial resolutions up to 3.125 km2. Spanning a record from 1979 to 2016, this approach has potential for novel use in areas of variable terrain, such as mountainous Dall Sheep habitat.

Associated Project(s): 

• Prugh-01

Poster Location ID: 25

Session Assigned: Wildlife and Ecosystem Services