Relationship between Aoshio, blue-green turbid water, and wind-driven current.

Applying a Simple Analytical Solution to Modelling Wind-Driven Coastal Upwelling of Two-Layered Fluid at the Head of Tokyo Bay, Japan

“…At long timescales of the northeasterly blowing wind, the two-layered fluid will be deflected to the right of the wind direction due to the Coriolis force. This simple hydrodynamic explanation to the blue tide occurrence was found to be consistent with some previous studies [5][6][7]9,12,15]. Although it seems difficult to determine the specific time at which the Coriolis force starts to play a role, this time scale could be simply estimated as two days in this study based on the numerical experiments of Matsuyama et al [15] and Ueno et al [28] concerning coastal upwelling in Tokyo Bay.…”

“…and |ζ(− 1 )| here (ζ (− 1 ) + |ζ(− 1 )| > h). Thus, Equation (6) could represent the minimum wind stress for the occurrence of blue tides on the northeast shore of the research area. It should also be noted that there are some simplifications and assumptions involved in the derivation of the analytical solution, but it gives a simple relation for characterizing the dependence of wind conditions on the stratification properties and geometrical properties of the two-layered fluid.…”

“…During this process, a large concentration of dissolved oxygen at the bottom is consumed, and the bottom water consequently becomes oxygen-depleted and even anoxic. On the other hand, along the seasonal temperature stratifications, fresh water inflows around the bay and intermittent precipitation result in a high-temperature, low-salinity upper water layer and a low-temperature, high-salinity lower water layer [6][7][8][9]. As a result, a stable density stratification forms in which the lighter upper water overlies the heavier lower water, hindering the vertical circulation that brings dissolved oxygen from the surface to the bottom and thus enhances the oxygen-depleted state of the lower water [5,8].…”

Minimum Wind Stress for the Occurrence of Blue Tide on the Southeast Shore of Tokyo Bay

“…Plenty of researches concerning blue tide have been carried out in the past from different perspectives (Gomyo et al, 1998;Ichioka et al, 2009;Kakino et al, 1987;Kataoka et al, 1989;Koibuchi & Isobe, 2007;Matsuyama et al, 1990;Nakatsuji et al, 1991;Nakatsuji et al, 1995;Otsubo et al, 1991;Sasaki et al, 1993;Sasaki et al, 1996). These research results are helpful to understand the mechanism of outbreak of blue tide phenomenon, and, based on them, this study presents the minimum wind stress for the occurrence of blue tide on the southeast shore of the bay by using an analytical solution in the context of a two-layered model.…”

Optical, biological, and chemical properties ofAoshio, hypoxic milky blue-green water, observed at the head of Tokyo Bay

“…The mortality of fish and benthic animals such as clams is often observed in that area (Kakino, 1986). The outbreak of aoshio usually coincides in time with the occurrence of temporarily northerly off-shore wind (Kakino et al, 1987).…”