Changes in Water Temperatures

From  ”State of physical, biological, and selected fishery resources of Pacific Canadian marine ecosystems in 2012

Diane Masson and Patrick Cummins of Fisheries and Oceans Canada compared temperature contours from a single station in the central deep basin of the Strait of Georgia since 2005 with salinity measurements taken at the lighthouse station at Entrance Island. This allows them to examine how temperature and freshness of the waters of the Strait have changed over time.

Figure 1 shows the types of temperature contour plots that can be produced using data collected from the Nanoose station in the central deep basin of the Strait of Georgia where, since 2005, temperature contours have been measured. 

Figure 1. Contours of temperature (oC) measured at the Nanoose station (central Strait of Georgia) since 2005.


Figure 2. Normalized negative salinity anomalies measured at the Entrance Island (blue) and anomalies of Fraser River discharge (red), for the period 1940-2011. Anomalies are computed relative to the climatological mean for 30-year period 1971-2000. A negative salinity anomaly indicates saltier water. 

In Figure 2, monthly surface salinity negative anomalies measured at Entrance Island as well as monthly Fraser River discharge are presented. The salinity anomalies at the surface of the strait are closely related to Fraser River discharge anomalies. During most of 2011, large freshwater influx from the river resulted in fresher than average surface waters.