Observations of vertical turbulent nitrate flux across the Kuroshio

Kaneko, Hitoshi; Yasuda, Ichiro; Komatsu, Kosei; Itoh, Susumu

doi:10.1002/grl.50613

Cited by 55 publications

(50 citation statements)

References 33 publications

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“…The observations suggest that the strong turbulence in the Kuroshio causes a diffusive nitrate flux of O(1-10 mmol N·m −2 ·day −1 ), which is 1-2 orders of magnitude greater than the previous estimate in the Kuroshio Extension Front (Kaneko et al, 2012(Kaneko et al, , 2013. Although the Kuroshio path modulates with time scales of weeks to months (Usui et al, 2013), the Kuroshio always flows near the continental shelf at several locations, such as the Okinawa Trough, Hyuganada Sea, off Tosa Bay, off Kii Peninsula, and east of Boso Peninsula.…”

Section: Discussionmentioning

confidence: 56%

How the Kuroshio Current Delivers Nutrients to Sunlit Layers on the Continental Shelves With Aid of Near‐Inertial Waves and Turbulence

Nagai

Durán

Otero

et al. 2019

Geophysical Research Letters

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The Kuroshio Current carries a large amount of nutrients in dark subsurface layer along the southern coast of Japan. However, due to lack of sufficient multidisciplinary high‐resolution observations, it has been unclear whether and how the subsurface nutrients are injected to sunlit layers on the continental shelf. In this study, using a state‐of‐the‐art tow‐yo microstructure profiler and nitrate measurements, we show that the Kuroshio flowing on the shelfbreak induces very strong turbulent dissipation rate ∼O(10−7W·kg−1) and diffusivity ∼O(10−3 m2·s−1) over an across frontal scale of 20–30 km. This strong turbulence could provide a diffusive nitrate flux to euphotic zone of >O(1 mmol N·m−2·day−1). As the Kuroshio steadily runs on the continental shelves along the path, the nutrient injection found in this study is a very important supply for biological production on the continental margin along the southern coast of Japan.

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Section: Discussionmentioning

confidence: 56%

How the Kuroshio Current Delivers Nutrients to Sunlit Layers on the Continental Shelves With Aid of Near‐Inertial Waves and Turbulence

Nagai

Durán

Otero

et al. 2019

Geophysical Research Letters

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“…4 is lower in the outside of the Kuroshio than that in the slope and in the axis of the Kuroshio (Kaneko et al 2012). As the result, the vertical nitrate diffusive flux at depths from 50 to 300 m is one to two orders higher in the slope and Kuroshio areas (10 -6 mmol N m -2 s -1 ) than in the gyre areas (10 -7 -10 -8 mmol N m -2 s -1 ) in the early spring observation (Kaneko et al 2013). These processes are suggested to lead to the spatial differences in surface N ?…”

Section: Vertical Diffusive Fluxmentioning

confidence: 80%

Seasonal and spatial contrast in the surface layer nutrient content around the Kuroshio along 138°E, observed between 2002 and 2013

et al. 2014

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Seasonal and spatial contrasts of nitrate ? nitrite (N ? N) concentrations in the slope area (the inshore area to the Kuroshio), Kuroshio and subtropical gyre areas were described by using data sets carried out along the O-line (138°E) between 34°45 0 N and 30°N over 11 years (2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013). The mean concentration of N ? N in the surface mixed layer during winter was elevated to 4.8 ± 2.7, 1.5 ± 1.6 and 0.7 ± 0.4 lM in the slope, Kuroshio and subtropical gyre areas, respectively, while it was depleted to\0.1 lM in all areas during summer. Applying regression analyses to the data, a significant negative correlation between N ? N concentration and temperature was found at any depths above 1000 m in both summer and winter in these areas, except for the summer surface depletive layers. The analyses also showed that the diffusive upward flux and the depth difference between the surface mixed layer and the 15-lM nitrate-isoconcentration depth were important factors to induce the seasonal contrast between winter and summer and horizontal contrast among the slope, Kuroshio and gyre areas in the N ? N concentration in the surface mixed layer. Since the nitrateisoconcentration depth is much shallower in the slope area than in the other two areas, the developing wintertime mixed layer reaches to the nitrate-rich water in the slope area, and that leads to a several micromolar increase in the surface N ? N concentration there.

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“…Since the results by Pelegrí and Csanady (1991) are similar to the results of our budget calculations (Tables 2 and 3) (i.e., nitrate concentration increased in the light layers and decreased in the dense layers), we believe that diapycnal mixing should be an important factor in controlling the change of nitrate along the Kuroshio. Recently, Kaneko et al (2013) calculated the vertical nitrate flux in the main stream of the Kuroshio from measured nitrate concentrations and the vertical viscosity coefficient estimated from field turbulent measurements. Their results indicated an upward nitrate flux from the depth of 300 m to the surface layer.…”

Section: A Budget Calculation For An Area Enclosed By Sections Asuka-mentioning

confidence: 99%

Spatial variations in the Kuroshio nutrient transport from the East China Sea to south of Japan

Guo

Zhu²,

Yu³

et al. 2013

Biogeosciences

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Abstract. Based on absolute geostrophic velocity, which was calculated using repeated hydrographic data of 39 cruises from 2000 to 2009 and nitrate concentrations measured in the same areas from 1964 to 2009, we obtained the temporally averaged nitrate flux (the product of velocity and nitrate concentration) and nitrate transport (integration of flux over one section) of four sections across the Kuroshio from the East China Sea (sections PN and TK) to an area south of Japan (sections ASUKA and 137E). In addition, we examined section OK east of the Ryukyu Islands in order to understand how the Ryukyu Current contributes to the

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Observations of vertical turbulent nitrate flux across the Kuroshio

Cited by 55 publications

References 33 publications

How the Kuroshio Current Delivers Nutrients to Sunlit Layers on the Continental Shelves With Aid of Near‐Inertial Waves and Turbulence

How the Kuroshio Current Delivers Nutrients to Sunlit Layers on the Continental Shelves With Aid of Near‐Inertial Waves and Turbulence

Seasonal and spatial contrast in the surface layer nutrient content around the Kuroshio along 138°E, observed between 2002 and 2013

Spatial variations in the Kuroshio nutrient transport from the East China Sea to south of Japan

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