Recent conditions highlight regional differences in temperature, salinity and dissolved oxygen between Strait of Juan de Fuca and Puget Sound sites under anomalous 2014-2017 climate patterns

Understanding impacts of climate change on Salish Sea water quality is critical yet challenging due to the complexity, strength and diversity of influences on circulation and mixing. Different extreme climate conditions in recent years (2014-2017) include record warm temperatures with reduced snow pack in 2014-2015 followed by a few years of alternating summer droughts with record rainy seasons. These conditions influenced marine water temperature, salinity and dissolved oxygen (DO) throughout the Salish Sea. Analyses reveal distinct differences in these key physical and chemical characteristics between Strait of Juan de Fuca sites and sites within Puget Sound basins. Extremely low DO water in the Strait not observed at neighboring sites in Puget Sound. This indicates that Puget Sound water exchange and circulation are responding to climate change impacts on the regional hydrological cycle. Lower stream flows are effecting seasonal exchange of ocean water masses under drought conditions, while extremely wet and stormy springs are changing the average salinity of Puget Sound basins and impacting the density structure. Following these physical fluctuations, DO conditions vary from season to season, with new anomalous lows occurring in the Strait and the extreme reaches of South Puget Sound. These conditions could reveal how biophysical drivers of Puget Sound water quality impact food web dynamics during adverse climate and ocean regimes. Local water quality issues that are exacerbated due to reduced circulation may be influencing distinct populations in different basins. We can use these basic biophysical properties to inform us about key drivers of regional differences in the Puget Sound food web.