Abstract
The hydrological sensitivity of snowmelt-dominated, high mountain
headwaters to climate change was investigated using a physically based
model to diagnose snow processes and headwater basin runoff response to
perturbations of the current climate in three well-instrumented mountain
research basins spanning the northern North American Cordillera.
High-resolution hourly meteorological observations were perturbed using
air temperature increases and precipitation changes and then used to
force comprehensive, mountain hydrological models created using the
modular, process-based Cold Regions Hydrological Modelling Platform
(CRHM) for each basin. Simulations using multiple elevations show that
both peak snowpack and annual runoff respond to warming and
precipitation changes and these responses vary with latitude. In all
three basins, the timing and magnitude of peak snowpack were sensitive
to changes in temperature and precipitation, but timing was most
sensitive to temperature. Annual runoff was far less sensitive to
temperature than the snow regime. The impacts of the range of warming
expected from North American climate model simulations on annual runoff,
but not peak snowpack, can be offset by the size of precipitation
increases projected for the future period 2041-2070. To offset the
impact of 2°C warming on annual runoff, precipitation would need to
increase by less than 5% in all three basins. To offset the impact of
2°C warming on peak snowpack, however, precipitation would need to
increase by 12% in Wolf Creek – Yukon Territory, 18% in Marmot Creek
– Canadian Rockies and an amount greater than the maximum projected at
Reynolds Mountain – Idaho. The role of increased precipitation as a
compensator for the impact of warming on mountain snow hydrology is more
effective at the high elevations and high latitudes. Increased
precipitation leads to resilient and strongly coupled snow and
hydrological regimes in cold regions and sensitive and weakly coupled
regimes in the low elevations and temperate climate zones.
Keywords: Climate change, mountain hydrology, North American
Cordillera, hydrological processes, cold regions, sensitivity analysis