El Niño‐Related Stratification Anomalies Over the Continental Slope Off Oregon in Summer 2014 and 2015: The Potential Vorticity Advection Mechanism Journal of Geophysical Research: Oceans

Over the continental slope off Oregon at the US West Coast, at 44.6°N, vertical stratification is found to be anomalously weak in July–August of 2014 and 2015 both in a regional ocean circulation model and conductivity–temperature–depth (CTD) profile observations. To understand the responsible mechanism, we focus on the layer between the isopycnal surfaces σθ = 26.5 and 26.25 kg m −3 that is found between depths 100 and 300 m and represents material properties characteristic of the slope poleward undercurrent and shelf-slope exchange. This layer thickness, about 50 m on average, can be twice as large during the above-mentioned periods. In the 2009–2018 model analysis, this anomaly is revealed over the continental slope only in summers