Observations of New, Large and Stable Abyssal Currents at Midlatitudes along 165°E

Abstract

Unexpectedly large and stable abyssal mean flow have recently been observed along 165°E, between 31° and 41°N. These results are based on two deployments of a moored array for approximately a year each. Time-averaged currents at 4000 m are about 5 ± 0.5 cm s?1 to the southwest near 41°N and 6 ± 0.9 cm s?1 to the northwest near 33°N, on opposite of the Kuroshio Extension. These mean flows were reproduced between array deployments to within a fraction of a cm s?1 and few degrees (True). At 41°N the abyssal mean kinetic energy is several times larger than eddy kinetic energy so that the flow visually does not reverse. At 33°N, near the southern edge of the Kuroshio Extension, the abyssal mean and eddy fields are of roughly the same amplitude. These result along 165°E are in contrast to similar observations along 152°E, where the abyssal zonal mean flows are notably less stable than at 165°E. However, estimates of the latitudinal and two-years averaged zonal flow components are approximately the same at both longitudes, typically in the range of 1.4 to 1.9 cm s?1 to the west. The new currents described here have not be observed previously and are not a feature of any proposed circulation scheme with which the author is familiar.