scholarly journals Frontogenesis and frontolysis of the subpolar front in the surface mixed layer of the Japan Sea

2014 ◽  
Vol 119 (2) ◽  
pp. 1498-1509 ◽  
Author(s):  
Ning Zhao ◽  
Atsuyoshi Manda ◽  
Zhen Han
Keyword(s):  
Mixed Layer ◽  
Japan Sea ◽  
Surface Mixed Layer ◽  
The Japan Sea

Horizontal and vertical movement of yellowtails Seriola quinqueradiata during summer to early winter recorded by archival tags in the northeastern Japan Sea

2020 ◽  
Vol 636 ◽  
pp. 139-156
Author(s):  
S Furukawa ◽  
A Kozuka ◽  
T Tsuji ◽  
H Kubota
Keyword(s):  
Fork Length ◽  
Movement Pattern ◽  
Japan Sea ◽  
Vertical Movement ◽  
Surface Mixed Layer ◽  
The West ◽  
Fishery Resource ◽  
Archival Tags ◽  
The Japan Sea ◽  
Seriola Quinqueradiata

Yellowtails Seriola quinqueradiata are an important fishery resource around Japan. Here we investigated the movement ecology and habitat utilization of this migratory fish. Archival tags were implanted in 26 adult yellowtails (61-90 cm in fork length) to examine their seasonal movement patterns and vertical distribution. Yellowtails were captured and released around Noto Peninsula in the Japan Sea on 27 May 2004. Eight individuals were recaptured more than 2 mo later, and we analyzed their daily position and vertical movement with ambient water temperature recorded in 60 or 120 s intervals. Most yellowtail individuals moved from the central coast of Japan to the north (from the west of Tsugaru Strait to the west of Hokkaido) in June. Individuals resided in the northern part of the Japan Sea from summer to mid-fall (late July to late October). Seasonal thermoclines developed during this northward movement and subsequent period of residency, with individuals primarily occupying the surface mixed layer during the daytime and at night; however, individuals made frequent short dives through the thermocline, especially during the daytime. These phenomena may be related to foraging based on the distribution of their prey. In late October, yellowtails started a rapid southward movement, primarily remaining in vertical thermal mixing coastal areas, and not entering the coldwater masses that formed offshore. This southward movement pattern might indicate that yellowtails avoid cold offshore water temperatures.

scholarly journals Nonseasonal Variations in Near-Inertial Kinetic Energy Observed Far Below the Surface Mixed Layer in the Southwestern East Sea (Japan Sea)

2021 ◽  
Vol 10 (1) ◽  
pp. 9
Author(s):  
Suyun Noh ◽  
SungHyun Nam
Keyword(s):  
Kinetic Energy ◽  
Mixed Layer ◽  
Surface Wind ◽  
Japan Sea ◽  
Relative Vorticity ◽  
East Sea ◽  
Total Strain ◽  
Surface Mixed Layer ◽  
Capture Process ◽  
Long Time

Near-inertial internal waves (NIWs) generated by surface wind forcing are intermittently enhanced below and within the surface mixed layer. The NIW kinetic energy below the surface mixed layer varies over intraseasonal, interannual, and decadal timescales; however, these variations remain unexplored, due to a lack of long-term, in situ observations. We present statistical results on the nonseasonal variability of the NIW kinetic energy 400 m below the surface mixed layer in the southwestern East Sea, using moored current measurements from 21 years. We used long time series of the near-inertial band (0.85–1.15 f) kinetic energy to define nine periods of relatively high (period high) and seven periods of relatively low (period low) NIW kinetic energy. The NIW kinetic energy average at period high was about 24 times higher than that at period low and those in specific years (2003, 2012–2013, 2016, and 2020) and decade (2010s) were significantly higher than those in other years and decade (2000s). Composite analysis revealed that negative relative vorticity and strong total strain significantly enhance NIW kinetic energy at 400 m. The relative vorticity was negative (total strain was positively enhanced) during seven (six) out of nine events of period high. NIW trapping in a region of negative relative vorticity and the wave capture process induce nonseasonal variations in NIW kinetic energy below the surface mixed layer. Our study reveals that, over intraseasonal, interannual, and decadal timescales, mesoscale flow fields significantly influence NIWs.

Characteristics of water mass under the surface mixed layer in Tsushima Straits and the southwestern Japan Sea in autumn

2008 ◽  
Vol 64 (4) ◽  
pp. 585-594 ◽  
Author(s):  
Tetsutaro Takikawa ◽  
Akihiko Morimoto ◽  
Goh Onitsuka ◽  
Atsushi Watanabe ◽  
Masatoshi Moku
Keyword(s):  
Mixed Layer ◽  
Water Mass ◽  
Japan Sea ◽  
Surface Mixed Layer ◽  
Tsushima Straits

Mixed Layer Models and Their Application to Water Quality Problems

1994 ◽  
Vol 29 (2-3) ◽  
pp. 221-232
Author(s):  
M.J. McCormick
Keyword(s):  
Water Quality ◽  
Mixed Layer ◽  
Thermal Structure ◽  
Mass Conservation ◽  
Eddy Diffusion ◽  
Rate Of Change ◽  
Surface Mixed Layer ◽  
Storm Events ◽  
Quality Model ◽  
Mixing Processes

Abstract Four one-dimensional models which have been used to characterize surface mixed layer (ML) processes and the thermal structure are described. Although most any model can be calibrated to mimic surface water temperatures, it does not imply that the corresponding mixing processes are well described. Eddy diffusion or "K" models can exhibit this problem. If a ML model is to be useful for water quality applications, then it must be able to resolve storm events and, therefore, be able to simulate the ML depth, h, and its time rate of change, dh/dt. A general water quality model is derived from mass conservation principles to demonstrate how ML models can be used in a physically meaningful way to address water quality issues.

scholarly journals Simulation of diurnal variability in vertical density structure using a coupled model

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
B. Yadidya ◽  
A. D. Rao ◽  
Sachiko Mohanty
Keyword(s):  
Mixed Layer ◽  
3D Model ◽  
Coupled Model ◽  
Wave Model ◽  
Andaman Sea ◽  
Surface Mixed Layer ◽  
Diurnal Variability ◽  
Rama Buoy ◽  
Vertical Displacements ◽  
Primary Advantage

AbstractThe changes in the physical properties of the ocean on a diurnal scale primarily occur in the surface mixed layer and the pycnocline. Price–Weller–Pinkel model, which modifies the surface mixed layer, and the internal wave model based on Garrett–Munk spectra that calculates the vertical displacements due to internal waves are coupled to simulate the diurnal variability in temperature and salinity, and thereby density profiles. The coupled model is used to simulate the hourly variations in density at RAMA buoy (15° N, 90° E), in the central Bay of Bengal, and at BD12 (10.5° N, 94° E), in the Andaman Sea. The simulations are validated with the in-situ observations from December 2013 to November 2014. The primary advantage of this model is that it could simulate spatial variability as well. An integrated model is also tested and validated by using the output of the 3D model to initialize the coupled model during January, April, July, and October. The 3D model can be used to initialize the coupled model at any given location within the model domain to simulate the diurnal variability of density. The simulations showed promising results which could be further used in simulating the acoustic fields and propagation losses which are crucial for Navy operations.

scholarly journals Niche partitioning by photosynthetic plankton as a driver of CO2-fixation across the oligotrophic South Pacific Subtropical Ocean

2021 ◽  
Author(s):  
Julia Duerschlag ◽  
Wiebke Mohr ◽  
Timothy G. Ferdelman ◽  
Julie LaRoche ◽  
Dhwani Desai ◽  
...  
Keyword(s):  
Mixed Layer ◽  
Niche Partitioning ◽  
Euphotic Zone ◽  
South Pacific ◽  
Niche Differentiation ◽  
Surface Mixed Layer ◽  
The South ◽  
The Core ◽  
Photosynthetic Eukaryotes ◽  
Phytoplankton Communities

AbstractOligotrophic ocean gyre ecosystems may be expanding due to rising global temperatures [1–5]. Models predicting carbon flow through these changing ecosystems require accurate descriptions of phytoplankton communities and their metabolic activities [6]. We therefore measured distributions and activities of cyanobacteria and small photosynthetic eukaryotes throughout the euphotic zone on a zonal transect through the South Pacific Ocean, focusing on the ultraoligotrophic waters of the South Pacific Gyre (SPG). Bulk rates of CO2 fixation were low (0.1 µmol C l−1 d−1) but pervasive throughout both the surface mixed-layer (upper 150 m), as well as the deep chlorophyll a maximum of the core SPG. Chloroplast 16S rRNA metabarcoding, and single-cell 13CO2 uptake experiments demonstrated niche differentiation among the small eukaryotes and picocyanobacteria. Prochlorococcus abundances, activity, and growth were more closely associated with the rims of the gyre. Small, fast-growing, photosynthetic eukaryotes, likely related to the Pelagophyceae, characterized the deep chlorophyll a maximum. In contrast, a slower growing population of photosynthetic eukaryotes, likely comprised of Dictyochophyceae and Chrysophyceae, dominated the mixed layer that contributed 65–88% of the areal CO2 fixation within the core SPG. Small photosynthetic eukaryotes may thus play an underappreciated role in CO2 fixation in the surface mixed-layer waters of ultraoligotrophic ecosystems.

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