P31     Changes in precipitation and snowpack across Alaska in a high-resolution future climate change simulation.

Newman, Andrew J., Research Applications Laboratory, National Center for Atmospheric Research, Monaghan, Martyn P. Clark, Center for Research Data & Digital Scholarship, University of Colorado, Kyoko Ikeda, Lulin Xue, Research Applications Laboratory, National Center for Atmospheric Research, and Jeff. R. Arnold, Climate Preparedness and Resilience Program, US Army Corps of Engineers

Alaska has warmed during the recent observational record and is projected to keep warming through the end of the 21st century in nearly every future emissions scenario and global climate model.  This will alter the partitioning of rain versus snow events, and may have potentially large impacts for the water cycle and land-surface processes across the state.  However, previous analyses of these impacts using dynamical models have relied on global climate model output or relatively coarse regional climate model simulations.  Projections of changes to the water cycle and land-surface processes in areas of complex orography and high land-surface heterogeneity, which are characteristic of Alaska, may thus be limited.  Here we present a 14-year future climate simulation for Alaska at 4-km grid spacing using the Weather Research and Forecasting (WRF) mesoscale atmospheric model.  A grid spacing of 4 km is sufficient to resolve orography across Alaska’s mountain ranges and the chosen model configuration yields a realistic representation of the seasonal and spatial evolution of precipitation, temperature, and snowpack.

The future climate simulation uses the Pseudo-Global Warming (PGW) approach, where the end of century ensemble mean monthly climate perturbations (CMIP5 RCP8.5) are used to incorporate the thermodynamic effects of future warming into the present-day climate as represented by ERA-Interim reanalysis data. We will discuss how some of the major components of the water cycle (e.g. precipitation, snowpack) are projected to change in this future scenario, and implications for future hydrologic response across the major watersheds in Alaska.  Examples include a significant shift from snow to rain throughout all seasons except DJF along with a nearly statewide loss of snow water equivalent except at the coldest and highest elevations.  An increase in winter episodic snowmelt events (ESEs) is also seen, even in the coldest months.