Climate Change and Its Impact on Seasonal Patterns of Puget Sound Circulation

In this research, we conduct an analysis of the circulation and transport in the Puget Sound with a focus on seasonal patterns under current and future scenarios. The coupled effects of the change in river flow characteristics and higher mean sea level are of concern due to potential impacts to coastal fisheries, water quality and circulations. Understanding the circulation pattern and estuarine exchange flows is an important step towards quantifying the impacts of future climate changes. Puget Sound estuary functions as a mixing zone that connects several major riverine freshwater inputs with ocean water. The circulation patterns are subject to differences in tidal amplitudes and phases of connected subbasin waters as well as the river runoff. In this study, we apply the FVCOM model for the entire Puget Sound-Georgia Basin region. A mass balance approach of flux calculation method, which is consistent with FVCOM model’s internal finite volume advection scheme, is used to compute the volume fluxes, fresh water fluxes and salt fluxes across vertical transects that connect several basins within the estuary and with outer domain. This method allows one to accurately keep track of the water mass balance in an unstructured grid model. With projected changes in snowpack melting and wind patterns over the region, river inputs will shift its seasonality away from Spring-Summer dominance. We quantify the impact of this riverine hydrological flow change on Puget Sound circulation patterns through flux analysis. The analysis will be presented in detail for year 2008 (current conditions) and year 2070 (projected conditions) based on hydrological loads corresponding to IPCC - A1B climate change scenario