Climate change impacts on maritime mountain snowpack in the Oregon Cascades

This study investigates the effect of projected
temperature increases on maritime mountain snowpack in
the McKenzie River Basin (MRB; 3041 km2) in the Cascades
Mountains of Oregon, USA. We simulated the spatial
distribution of snow water equivalent (SWE) in the MRB
for the period of 1989–2009 with SnowModel, a spatiallydistributed,
process-based model (Liston and Elder, 2006b).
Simulations were evaluated using point-based measurements
of SWE, precipitation, and temperature that showed Nash-
Sutcliffe Efficiency coefficients of 0.83, 0.97, and 0.80, respectively.
Spatial accuracy was shown to be 82% using
snow cover extent from the Landsat Thematic Mapper. The
validated model then evaluated the inter- and intra-year sensitivity
of basin wide snowpack to projected temperature increases
(2 degrees C) and variability in precipitation (±10 %). Results
show that a 2 degrees C increase in temperature would shift the
average date of peak snowpack 12 days earlier and decrease
basin-wide volumetric snow water storage by 56 %. Snowpack
between the elevations of 1000 and 2000m is the most
sensitive to increases in temperature. Upper elevations were
also affected, but to a lesser degree. Temperature increases
are the primary driver of diminished snowpack accumulation,
however variability in precipitation produce discernible
changes in the timing and volumetric storage of snowpack.
The results of this study are regionally relevant as melt water
from the MRB’s snowpack provides critical water supply
for agriculture, ecosystems, and municipalities throughout
the region especially in summer when water demand is
high. While this research focused on one watershed, it serves as a case study examining the effects of climate change on
maritime snow, which comprises 10%of the Earth’s seasonal
snow cover.