Salish Sea Marine Survival Project

27 In late 2013, scientists started to notice unusually warm sea surface temperatures in the Gulf of Alaska; and by the fall of 2014, these warmer waters extended along vast portions of the Canadian and US coasts. Warming persisted during most of 2015 and into 2016. This mass of warm water, the size of Canada, was named the "Blob" and exhibited sea surface temperatures up to 2.5 degrees Celsius above the 1981-2010 average — an unprecedented observation. The development of this warm water has been attributed largely to an unusual weather pattern which featured higher-than-normal pressure over the ocean (Figure 1). This ridge of high pressure reduced the number and intensity of storms reaching land, resulting in reduced precipitation along the west coast, and diversion of cold Arctic air into the middle and eastern parts of Canada and the US. The increased temperatures on the surface of the ocean caused the air just above to heat up and stagnate, resulting in greatly weakened coastal winds which were no longer able to push the warm top layer of the Pacific Ocean away from the shoreline. The result was a greatly reduced rate of heat transfer from the ocean to the atmosphere, and slower movement of cooler water into the area of the Blob. This situation was exacerbated by an El Niño event in 2015. What initially caused this ridge of high pressure is still under some debate. However, using climate modeling, researchers have recently concluded that this climate event was 53 times more likely to have happened, particularly in the Arctic, as a result of human-induced climate change. PSF'S CITIZEN SCIENCE OCEANOGRAPHY PROJECT The Citizen Science Oceanography Project, initiated under SSMSP, examined changes in the Strait of Georgia at partic- ularly high spatial and temporal resolution over this very dynamic period of time 2015-2018. Temperature variations were greatest in the upper few meters of water, ranging from as cold as 6° C in March to over 20° C in summer months. Temperatures below 17° C are best for juvenile salmon early rearing. Given that surface waters were warmer than this in July and August for all three years, it appeared that waters as deep as 10 m in the summer were not good habitat for salmon. However, in all three years, there were regional variations with favourable water temperatures found in highly mixed areas of the Strait, particularly in the northern Strait where tidal flow through Discovery Passage causes extensive mixing. Temperature was also shown to vary significantly between the years, especially at the deeper depth ranges, with 2017 colder at depth (approximately 1.5° C cooler) than 2015 and 2016. OCEANOGRAPHIC CONDITIONS DURING SSMSP: THE STRAIT OF GEORGIA OCEANOGRAPHIC CONDITIONS DURING "THE BLOB" 2014-2017 Canadian Salish Sea Marine Survival Project (SSMSP) pilot studies began in 2014 and the full program was implemented in 2015 through 2018. Over these 4 years, we have seen some unusual oceano- graphic changes occurring along the west coast of North America. These changes had major impacts in the North Pacific Ocean and will likely provide some interesting comparisons during the SSMSP studies and analyses! Figure 1. The persistent ridge of high pressure has affected weather patterns. Image derived from NOAA. difference from average 200-millibar geopotential height (meters) -80 0 80 -3.0 0.0 3.0 Figure 2. This image shows unusually high sea-surface temperatures in the Pacific Ocean in May 2015 as compared to the 2002–2012 average. Image is from the American Geophysical Union. Sea Surface Temperature Anomaly (SSTA) May 2015 degrees Celsius

• Cover