Sub‐mesoscale coastal eddies observed by high frequency radar: A new mechanism for delivering nutrients to kelp forests in the Southern California Bight

Sub‐mesoscale eddies are described along the mainland coast of the Santa Barbara Channel based on observations from a network of high frequency (HF), current‐measuring radars and near‐shore moorings. The eddies are 4–15 km in diameter and typically last about 2 days, although some last up to 6 days. Most eddies within the radar coverage area are anti‐cyclonic with relative vorticities of −0.4 f to −0.8 f where f is the Coriolis parameter, but cyclonic eddies are also observed. Moored observations over the inner shelf (12 m water depth) of a sequence of two eddies in December 2001 show an increase in nitrate plus nitrite from the background levels of 1–2 μM to a maximum of 10–12 μM when the eddies are present. We speculate that these eddies are an important transport mechanism for nutrients and biogenic particles to inner shelf ecosystems of the Southern California Bight.