Regional measures of sea surface temperature, atmospheric temperatures, and waves
The 2014-2016 marine heatwave began with the formation of a warm ‘blob’ off of the west coast of North America, which was followed by an intense El Niño (Di Lorenzo & Mantua 2016). This led to a multiyear MHW that was strongly felt along Central Coast BC. Air and water temperature measurements from three BC lightstations illustrate the scale and severity of the heatwave in this region (Fig. 1). The heatwave was sustained from May 2014 to November 2017, longer than sites further south (e.g., California and Mexico: (Arafeh-Dalmau et al. 2019; Sanford et al. 2019) but consistent with patterns elsewhere on the BC coast (Starko et al. 2019). In a similar fashion, air temperatures were anomalously high from early 2014 through the end of 2016, demonstrating that this heatwave was extreme both oceanographically and atmospherically (Swain et al. 2017). This MHW rivaled the severity of the 1997/1998 El Niño for both air and water temperature in this region and represents the longest set of heatwaves in a time series of SST dating to the 1930s (Fig. S1). During the heatwave, daily SST and air temperature anomalies regularly exceeded 2.5°C.
Atmospheric temperatures on Calvert Island during the study period also reflect the anomalous conditions of the 2014-2016 NE Pacific MHW (Fig. S4). Temperatures tended toward positive temperature anomalies relative to mean conditions from Fall 2014 through Spring 2016.