High-Resolution Future Climate Change Simulation in Alaska Using a Pseudo–Global Warming Scenario

Alaska has warmed during the recent observational record and is projected to keep warming through the end of the 21^st century in nearly every future emissions scenario and global climate model. This will drive continued thawing of permafrost-rich soils and 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, a 14-year current and future climate simulation pair for Alaska at 4-km grid spacing using the Weather Research and Forecasting (WRF) mesoscale atmospheric model is presented. 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 compared to previous studies across Alaska and the contiguous US.

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. Changes in major components of the water cycle (e.g. precipitation and extreme events, snowpack, ET) are projected to change in sometimes significant ways in this future scenario, and implications for future hydrologic response across the major watersheds in Alaska will be discussed.