Factors affecting San Juan Channel and Puget Sound water properties during fall 2014

Abstract

Estuarine density gradient circulation patterns depend on seasonal and tidal temperature and salinity shifts. Changes to these properties affect the residence time and flushing of each fjord-like basin. Abnormal temperature and river discharge measurements in the Puget Sound in the fall of 2014 provided an interesting context to study the seasonal fall transition features from upwelling to downwelling. Using a CTD over the 7 week sampling period we looked at temperature and salinity in the San Juan Channel as well as October 23-31 in the Strait of Juan de Fuca (SJF) and Puget Sound basins. The Fall Transition occurred October 12th; our data showed evidence of the shift a week later in the San Juan Channel. External factors such as extensive freshwater input and abnormal SST off the coast interfered with typical temperature and salinity dynamics after the fall transition. Surface waters sampled in the SJF were much higher than predicted. The combination of seasonal and global climate forcing caused temperatures to be warmer after the transition with depth in the SJF and Hood Canal. San Juan Channel measured 1 - 2º C warmer than the 10 year Pelagic Ecosystem Function baseline, and was 1 - 2º C cooler than measurements throughout Puget Sound.