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 mu M to a maximum of 10 - 12 mu M 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.