Evidence for the Existence of a North Hawaiian Ridge Current

Abstract

Two different datasets are examined for information about the existence and characteristics of the North Hawaiian Ridge Current (NHRC). The pan-Pacific drifter dataset shows a mean NHRC to be confined to within about 100 km of the northern side of the Hawaiian Ridge. A close look at the distribution of the data shows that the current is mostly confined in time to a two-month period in the fall of 1991. MBT data from the Trade Wind Zone Oceanography Pilot Study conducted in the mid-1960s were also examined. Of the 14 cruises with sections north of the Hawaiian Ridge, 5 showed evidence of northwestward flow along the ridge. Of those 5, one was associated with northward meandering of the North Equatorial Current. It is thus suggested that the NHRC is highly intermittent. There are three related hypotheses for the formation of the NHRC, 1) propagation of Rossby waves westward into the ridge, 2) forking of the North Equatorial Current, and 3) as a western boundary current for the eastern Pacific north of 18°N. Evidence is presented pointing to hypothesis 2 as a plausible mechanism.