A Model Simulation of Future Oceanic Conditions along the British Columbia Continental Shelf. Part I: Forcing Fields and Initial Conditions

Abstract

Techniques for, and the results of, downscaling forcing and initial fields for an ocean-only regional climate model of the British Columbia continental shelf are presented. Fields from one regional-global model combination within the North American Regional Climate Change Assessment Program archive are shown to be representative of a larger ensemble of eight. Because model winds over the baseline period of 1970 to 1999 represent upwelling favourable conditions poorly, a strategy of computing future-minus-contemporary anomalies and adding them to the analogous values used in a recent hindcast simulation for the same region is justified and adopted. Average surface air temperatures over the future period of 2040 to 2069 are projected to be warmer for all months, with those in January generally having the highest increases and those in June the lowest. Because average precipitation is generally projected to increase in winter and decrease in summer, total freshwater discharges follow a similar pattern, increasing by about 10% in all months except June to August when they are projected to decrease by up to 10%. Though projected changes to the seasonally averaged heat flux are shown here, the consequence of applying all these forcing and initial fields to a circulation model of the British Columbia continental shelf is described in a subsequent companion manuscript.