Distribution of plankton related to the mesoscale physical structure within the surface mixed layer in the southwestern East Sea, Korea

Abstract. In this article, we describe physical parameters structures and different water masses using CTD measurements in southwestern part of the Caspian Sea (CS) in adjacent to Anzali Port (AP). CTD profilings were conducted along a transect perpendicular to the coastline over 13 stations from the coast down to 720 m in winter 2008. According to the results the continental shelf waters are located in surface mixed layer. Surface mixed layer extends itself down to almost 100 m in outer areas of the continental shelf with a weak seasonal thermocline layer between 80 to 140 m. Freshwaters inflow of local rivers is clearly seen outside continental shelf at the surface layers. Investigating the dissolved oxygen reveals that winter convection is traceable down to 500 m in the lateral waters over the shelf break. Among the deeper stations that are located in continental rise and abyssal plain, 350 m seems to be threshold for penetration of seasonal changes; therefore deeper waters tend to be impermeable against seasonal variances. Despite to the small variations, stability is positive in most region of the study area and temperature plays an important role in static stability and in triggering the lateral mixing. In view of both temperature-salinity and temperature-oxygen distributions in the southwestern part of the CS, three different water masses are separable in cold phase. Snapshot observation of physical properties in the early winter 2008, to some extent revealed that a mixing was triggered at least in the lateral waters of the study area.

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Snapshot observation of the physical structure and stratification in deep-water of the South Caspian Sea (western part)

Ocean Science ◽

10.5194/os-6-877-2010 ◽

2010 ◽

Vol 6 (4) ◽

pp. 877-885 ◽

Cited By ~ 6

Author(s):

P. Ghaffari ◽

H. A. Lahijani ◽

J. Azizpour

Keyword(s):

Continental Shelf ◽

Mixed Layer ◽

Caspian Sea ◽

Static Stability ◽

Physical Structure ◽

Water Masses ◽

Physical Parameters ◽

Surface Mixed Layer ◽

The Caspian Sea ◽

Southwestern Part

Abstract. The physical parameters structures and different water masses using CTD measurements in southwestern part of the Caspian Sea (CS) adjacent to Anzali Port (AP) are investigated. CTD profiles were conducted along a transect perpendicular to the coastline on 13 stations from the coast down to 720 m on 22 January 2008. According to the results the continental shelf waters are located in the surface mixed layer. The surface mixed layer extends itself down to almost 100 m in outer areas of the continental shelf with a weak seasonal thermocline layer between 80 to 140 m Freshwaters inflow of local rivers is clearly seen outside the continental shelf at the surface layers. Investigating the dissolved oxygen reveals that winter convection is traceable down to 500 m in the lateral waters over the shelf break. Among the deeper stations that are located in continental rise and abyssal plain, 300 m seems to be a threshold for penetration of seasonal changes; therefore deeper waters tend to be impermeable against seasonal variances. Despite the small variations, stability is positive in the study area and temperature plays an important role in static stability and in triggering the lateral mixing. In view of both temperature-salinity and temperature-oxygen distributions in the southwestern part of the CS, two different water masses are separable in cold phase. Snapshot observations of physical properties in the early winter 2008, to some extent revealed that a mixing was triggered at least in the lateral waters of the study area.

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

Journal of Marine Science and Engineering ◽

10.3390/jmse10010009 ◽

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.

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Chalk-Ex: Transport of Optically Active Particles from the Surface Mixed Layer

10.21236/ada444169 ◽

2005 ◽

Author(s):

Albert J. Plueddemann

Keyword(s):

Mixed Layer ◽

Optically Active ◽

Surface Mixed Layer ◽

Active Particles

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Mixed Layer Models and Their Application to Water Quality Problems

Water Quality Research Journal ◽

10.2166/wqrj.1994.015 ◽

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.

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

Scientific Reports ◽

10.1038/s41598-021-90426-w ◽

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.

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

The ISME Journal ◽

10.1038/s41396-021-01072-z ◽

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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