Strong vertical mixing in the Urup Strait

Abstract

Microstructure measurements were conducted in one of the Kuril Straits in the summer of 2007. Over the course of 1 day of repeated observations across the Pacific side of the steep sill of the Urup Strait, extremely strong mixing was observed during periods of Pacific‐ward (down‐sill) flows and during the transition from Pacific‐ward to Okhotsk‐ward (up‐sill) flows, with a turbulent energy dissipation rate ɛ of 10−6 to 10−5 W kg−1 and vertical diffusivity of 10−1 to 5 × 10−1 m2 s−1. During the period of strong mixing, we observed homogeneous layers with a thickness of 300–600 m and potential density of 26.6–26.7 σθ, occupying the entire water column in one case. High values of ɛ within this layer indicate the injection of diapycnal flows from the upper and lower layers, possibly contributing to southward intrusion of intermediate water into the subtropical gyre.

Evolution and modulation of a poleward‐propagating anticyclonic eddy along the Japan and Kuril‐Kamchatka trenches

“…[] demonstrated the intensification of an ACE located near Bussol’ Strait due to its interaction with low‐potential vorticity water flowing out from the Sea of Okhotsk. As low‐potential vorticity water formed by intense tidal mixing around the Kuril Islands [e.g., Itoh et al ., ; Yagi and Yasuda , ] flows along the Japan and Kuril‐Kamchatka trenches, the ACEs along the trenches could be affected by this water mass.…”

Intensive mixing along an island chain controls oceanic biogeochemical cycles

“…This resulted in a high diss‐Fe/N ratio (approximately 0.05) in water shallower than 26.6 σ θ isopycnal surface (Figure d). Strong diapycnal tidal mixing at the Kuril Straits redistributes these Fe‐ and nutrient‐rich intermediate water across a wide range of densities (Figures b, b, and c), as discussed in section 3.1 [ Ono et al ., ; Itoh et al ., , ; Yagi and Yasuda , ]. The section profiles (Figures b and d) and vertical profiles at Bussol' Strait (Figures 4a–4d) indicate that strong vertical tidal mixing in the Kuril Straits transports Fe and nutrients from deep water to water shallower than 26.6 σ θ isopycnal surface and determines the diss‐Fe/N ratio (Figure d).…”

“…[11] Previous studies have shown that the strong vertical tidal mixing that reaches down to the OSIW occurs around the Kuril Straits [Yamamoto-Kawai et al, 2004;Nakamura and Awaji, 2004]. Direct observations of turbulence reported by Itoh et al [2010Itoh et al [ , 2011 and Yagi and Yasuda [2012] document strong vertical mixing at the straits due to interaction between the complicated topography and strong diurnal tidal currents, and the diffusivity there is 4 orders of magnitude higher (maximum diffusivity over 1 × 10 À1 m 2 s À1 ) than in the open ocean. The diapycnal mixing around the straits strongly affects the temperature, salinity, and dissolved oxygen properties from the surface to the deep layer [Ono et al, 2007] and strongly influences the formation of North Pacific Intermediate Water (NPIW) [Talley, 1991;Wong et al, 1998;Nakamura and Awaji, 2004].…”

Dynamical Ocean Response Controlling the Eastward Movement of a Heat Content Anomaly Caused by the 18.6‐Year Modulation of Localized Tidally Induced Mixing

“…Numerical models assimilating altimeter data suggest that a large amount of barotropic tidal energy is dissipated around the sills separating the northern North Pacific and its marginal seas, that is, the Okhotsk Sea (Tanaka et al, ) and the Bering Sea (Foreman et al, ). Strong mixing has indeed been observed around those sills (e.g., Itoh et al, , ; Yagi & Yasuda, , ). We refer to this tidally induced strong mixing as “localized mixing,” and such mixing influences not only water masses in adjacent regions but also large‐scale circulation in the North Pacific (Nakamura et al, ; Tatebe & Yasuda, ; Osafune & Yasuda, ).…”