Projecting Future Climate States for the Salish Sea in Support of the Management of local Ecosystems and Fisheries

Projections of the future ocean state for Canada's Salish Sea are necessary to understand the effects of climate change on ecosystems, fisheries, and aquaculture providing critical information on likely future conditions and the ability to adaptively manage fisheries resources, ecosystems and significant areas. A multi-stage downscaling system is under development to improve our understanding of climate impacts for the Salish Sea and to generate actionable climate data for decision makers. Climate models are global and, therefore, are restricted to coarse resolutions on the order of 100km. The narrow straits and channels and complex bathymetry of the Salish Sea are modelled using a high-resolution ocean model known as the SalishSeaCast (500m). To drive the ocean model, the atmospheric climate forcing will be downscaled to a meaningful resolution. This project compares statistical and dynamical downscaling methods for downscaling the driving atmospheric fields to determine which method produces a more realistic ocean state. The downscaled fields will be used to analyze changes between a hindcast period (1986-2005) and future period (2046-2065) under two climate scenarios: the moderate mitigation representative concentration pathway (RCP) 4.5 and the no mitigation scenario RCP 8.5. The SalishSeaCast will be enhanced with a module for benthic respiration to improve the representation of biogeochemistry. The study will quantify changes in key stressors (e.g. temperature, oxygen, pH) and create maps of change to highlight ecologically significant areas for the purposes of conservation and protection. Additionally, we will investigate the impact of changing freshwater discharge on the Salish Sea marine ecosystem by conducting sensitivity tests using the recently available hydrological model projections of future discharge from the Fraser River under both future scenarios.