Near-term Intensification of the Hydrological Cycle in the United States

Wednesday, 16 December 2015: 14:10
3003 (Moscone West)
Moetasim Ashfaq1, Deeksha Rastogi1, Rui Mei1, Shih-Chieh Kao2, Bibi S Naz1 and Sudershan Gangrade1, (1)Oak Ridge National Laboratory, Oak Ridge, TN, United States, (2)Oak Ridge National Laboratory, Environmental Sciences Division, Oak Ridge, TN, United States
We present state-of-the-art near-term projections of hydrological changes over the continental U.S. from a hierarchical high-resolution regional modeling framework. We dynamically downscale 11 Global Climate Models (CCSM4, ACCESS1-0, NorESM1-M, MRI-CGCM3, GFDL-ESM2M, FGOALS-g2, bcc-csm1-1, MIROC5, MPI-ESM-MR, IPSL-ESM-MR, CMCC-CM5) from the 5th phase of Coupled Model Inter-comparison Project at 4-km horizontal grid spacing using a modeling framework that consists of a regional climate model (RegCM4) and a hydrological model (VIC). All model integrations span 41 years in the historic period (1965-2005) and 41 years in the near-term future period (2010-2050) under RCP 8.5. The RegCM4 domain covers the continental U.S. and parts of Canada and Mexico at 18-km horizontal grid spacing whereas the VIC domain covers only the continental U.S. at 4-km horizontal grid spacing. Should the emissions continue to rise throughout the next four decades of the 21st century, our results suggest that every region within the continental U.S. will be at least 2°C warmer before the mid-21st century, leading to the likely intensification of the regional hydrological cycle and the acceleration of the observed trends in the cold, warm and wet extremes. We also find an overall increase (decrease) in the inflows to the flood-controlling (hydroelectric) reservoirs across the United States, raising the likelihood of flooding events and significant impacts on the federal hydroelectric power generation. However, certain water-stressed regions such as California will be further constrained by extreme dry and wet conditions; these regions are incapable of storing rising quantities of runoff and wet years will not necessarily equate to an increase in water supply availability. Overall, these changes in the regional hydro-meteorology can have substantial impacts on the natural and human systems across the U.S.