Deep‐sea currents off northern California

Abstract

Current meter records from 14 moorings in the deep‐sea basin (3000–4500 m deep) south of the Mendocino Fracture Zone are analyzed. All moorings had current meters between 200 m and 500 m above the bottom, and some extended to within 150 m of the surface. There were high vertical correlations between measurements on the same mooring within 1500 m of the bottom and within 800 m of the surface but almost no significant correlation in the horizontal. In the basin the presence of eddies appears strongest at depths below 1200 m. Several of the records exceed 3 years in length, and one extended for 5 years. Spectral analysis of these shows that most of the kinetic energy below 3000 m is in the temporal mesoscale (periods of 31 to 120 days), while the spectral estimates in the upper 1000 m are dominated by longer time scales. Only in the deep records is there a significant southward mean flow. Neither a mean California Current nor a poleward undercurrent is apparent in the shallower data (above 1250 m). The currents in the upper 500 m nearest the continental margin are influenced by the presence of cold filaments originating near Point Arena.