Cold halocline in the northern California Current: An invasion of subarctic water

Abstract

Subsurface upper ocean waters off Oregon and Vancouver Island were about 1°C cooler in July 2002 than in July 2001. The anomalously cool layer coincides with the permanent halocline which has salinities of 32.2 to 33.8, suggesting an invasion of nutrient-rich Subarctic waters. The anomalously cool layer lies at 30-150 m. The cool anomaly is likely caused by stronger southward flow in the California Current and weaker northward flow in the Alaska and Davidson Currents during spring 2002. Other factors may include reduced coastal downwelling in late winter and early spring 2002, enhanced eastward flow in the Subarctic Current, and enhanced winter mixing offshore.