Microstructure measurements in the mid-depth waters of the North Pacific

Abstract

[1] Microstructure measurements from the surface down to maximum depths of ∼2000 m were carried out at 28 locations in the interior of the North Pacific. Special attention was directed to the diapycnal diffusivities Kρ in the significant generation regions of the semidiurnal internal tide such as the Aleutian Ridge, the Hawaiian Ridge, and the Izu-Ogasawara Ridge. In the profiles obtained near the Aleutian Ridge, only a few turbulent patches with ɛ ≥ 10−9 Wkg−1 were detected and Kρ was generally less than 10−5 m2s−1. In the profiles obtained near the Hawaiian Ridge, many turbulent patches with ɛ ≥ 10−9 Wkg−1 were observed, although Kρ was generally of the order of 10−5 m2s−1. Along the Izu-Ogasawara Trough running in parallel with the Izu-Ogasawara Ridge, in contrast, remarkably intense turbulent mixing (ɛ ∼ 10−8 Wkg−1, Kρ = 10−4 ∼ 10−3 m2s−1) was common throughout the observed water depth.