Residual currents over a uniform slope due to breaking of internal waves in a two‐layer system

Abstract

[1] Residual currents due to internal wave breaking on a uniform slope were investigated in a two-layer system using laboratory experiments and numerical computations for different layer configurations. Internal wave-induced currents over a slope were measured in an experimental tank using PIV and also reproduced by a hydrodynamic model to quantify the detailed velocity field. The present results reveal that the critical level derived from the KdV theorem is a useful parameter for classifying the dynamics of internal waves breaking over a slope. As the horizontal distance from the critical level point to the internal wave breaking point increases, internal waves break more dynamically over the slope. Consequently, residual currents are enhanced near the breaking point. These findings increase our capacity to understand flux paths of biological and chemical substances in the stratified coastal ocean.Citation: Nakayama, K., T. Shintani, K. Kokubo, T. Kakinuma, Y. Maruya, K. Komai, and T. Okada (2012), Residual currents over a uniform slope due to breaking of internal waves in a two-layer system,

Adaptive management in Kushiro Wetland in the context of salt wedge intrusion due to sea level rise

“…The validity of Fantom3D in the Kushiro Wetland was investigated by comparison to field observations (Nakamoto et al, 2011(Nakamoto et al, , 2012. Also, the validity of Fantom3D was confirmed in the application to stratified flow field (Maruya et al, 2010;Shintani and Nakayama, 2010;Nakayama et al, 2012). It should be noted that salt wedge intrusion was observed in field observations to reach the river mouth only in 2009 (Nakamoto et al, 2011).…”

“…Fantom3D is an objectoriented hydrodynamic model for the analysis of environmental fluid mechanics (Maruya et al, 2010;Shintani and Nakayama, 2010;Nakayama et al, 2012). The computational scheme is similar to Nakayama et al (2006), where attention was given to analysis of the stratified flow field.…”

“…A three-dimensional numerical model, Fantom3D, was applied to evaluate salt wedge intrusion when SLR occurs (Maruya et al, 2010;Shintani and Nakayama, 2010;Nakayama et al, 2012). Fantom3D is an object-oriented hydrodynamic simulator that through the use of parallel computing is able to clarify the potential for salt wedge intrusion along the Kushiro River due to SLR.…”

Horizontal and residual circulations driven by wind stress curl in Tokyo Bay

“…A three‐dimensional nonhydrostatic model, FANTOM3D, was used to clarify the role of negative wind curl on the occurrence of the depression of the isopycnals due to Ekman transport [ Maruya et al ., ; Nakayama et al ., ; Nakamoto et al ., ] and the associated anticyclonic horizontal circulation. FANTOM3D is an object‐oriented programming model for the analysis of environmental fluid mechanics.…”

Projection of “strong wind” events related to recovery from hypoxia in Tokyo Bay, Japan

“…The sludge and the polluted sediments lead to consumption of dissolved oxygen (DO), which can lead to hypoxia when stratification suppresses the supply of DO-saturated surface water to the lower layers of the bay head (Wolanski, 2006). Since hypoxia is harmful to many aquatic organisms, upwelling of hypoxic water under certain wind conditions or vertical mixing due to internal wave breaking can have severe ecological consequences (Stevens and Imberger, 1996;Maruya et al, 2010;Nakayama and Imberger, 2010;Nakayama et al, 2012). Even though enclosed bays are connected to the open ocean where nutrient concentrations are generally low, the exchange of water between the inner bay and the open ocean is sometimes suppressed by the shape of the bay, such that nutrients may accumulate and enhance eutrophication (Okada et al, 2011).…”