Coarse-grid (100-200 km) global climate model ensemble simulations of the SRES A1B emissions scenario were regionally downscaled to a 12-km grid using the Weather Research and Forecasting model for the period 1969-2069 (see below). These results were used to: 1) analyze the future potential changes and variability of coastal upwelling winds, and 2) provide forcing fields to a Regional Ocean Model System (see below) used to simulate the circulation and biophysics of the Salish Sea, including Puget Sound, and the coastal ocean. By comparing circa-1990 and circa-2050 climate scenarios for the environmental conditions that promote Alexandrium blooms (see temperature-gradient-bar work by Bill et al. by clicking on the "field and lab" tab to the left of your screen), we disentangle the effects of three climate pathways: 1) increased local atmospheric heating, 2) changing riverflow magnitude and timing, and 3) changing ocean inputs associated with changes in upwelling-favorable winds. Future warmer sea surface temperatures in Puget Sound from increased local atmospheric heating clearly increase the maximum growth rates that can be attained by Alexandrium during the bloom season as well as the number of days with conditions that are favorable for bloom development. This could lead to 30 more days a year with bloom-favorable conditions by 2050. In contrast, changes in surface salinity arising from changes in the timing of riverflow have a negligible effect on Alexandrium growth rates, and the behavior of the coastal inputs in the simulations suggest that changes in local upwelling will not have major effects on sea surface temperature or salinity or Alexandrium growth rates in Puget Sound.
Change in mean summer temperature (future scenario minus present-day scenario, averaged May through September) along a transect line from Admiralty Inlet through the Main Basin of Puget Sound. From Moore et al. submitted.
Differences between the present-day and future (A) growth and (B) bloom duration maps for Alexandrium in Puget Sound. Differences are calculated for the bloom season (May through October). From Moore et al. submitted.