The studied sites (Sites 1018, 1020, and 1021) are situated at ~40°N, where the California Current flows to the south (Fig. 1). The California Current, which is formed at the Polar Front as the edge of the subtropical gyre, brings relatively cold water to this region.
This region is affected by Pacific high pressure all through the year; especially in summer, this high pressure creates strong northwest winds, which cause an enhancement of Ekman upwelling in the northern coastal region. In winter, however, wind stress is weakened because the Aleutian low-pressure cell gains power; subsequently, coastal upwelling is also weakened and moves southward.