scholarly journals A Numerical Analysis on Coral Larval Networks across Reef Areas on the Northwest Coast of Okinawa Main Island, Japan

2021 ◽  
Vol 945 (1) ◽  
pp. 012030
Author(s):  
Kimika Takeyasu ◽  
Yusuke Uchiyama ◽  
Xu Zhang ◽  
Kosei Matsushita ◽  
Satoshi Mitarai
Keyword(s):  
High Resolution ◽  
Ocean Circulation ◽  
Mixed Layer ◽  
Short Distance ◽  
Northwest Coast ◽  
Surface Mixed Layer ◽  
Lagrangian Particle ◽  
Coral Larvae ◽  
Main Island ◽  
Tracking Model

Abstract Coral bleaching has recently occurred extensively over the world’s oceans, primarily due to high water temperatures. Mesophotic corals that inhabit at depths of approximately 30–150 m are expected to survive during bleaching events and to reseed shallow water corals afterward. In particular, in Okinawa, Japan, mesophotic coral ecosystems (MCEs) have been reported to serve as a refuge to preserve genotypic diversities of bleaching-sensitive corals. Connectivity of larval populations between different habitats is a key element that determines the area to be conserved for desirable coral ecosystems. Coral larvae generally behave passively to the surrounding currents and are transported by the advective and dispersive effects of ambient ocean currents. Thus, numerical ocean circulation models enable us to quantify connectivity with detailed spatiotemporal network structures. Our aim in this study is to quantify the short-distance and vertical connectivity of coral larvae in reef areas on the northwest coast of Okinawa Main Island. For the reason that both short-distance and vertical larval transport are influenced by complex nearshore topography, a very high-resolution 3-D circulation model is required. Therefore, we developed a quadruple nested high-resolution synoptic ocean model at a lateral spatial resolution of 50 m, coupled with an offline 3-D Lagrangian particle-tracking model. After validation of the developed model, short-distance horizontal coral connectivity across reef areas on the northwest coast was successfully evaluated. Furthermore, a series of Lagrangian particle release experiments were conducted to identify the vertical coral migration and 3-D connectivity required for the preservation of MCEs. The model revealed that coral larvae released from the semi-enclosed areas tended to remain near the source area, whereas they were diffused and dispersed gradually with time. The mesophotic corals were dispersed vertically to the deeper zone below the mixed layer, while upward transport occurred to induce the mesophotic corals to emerge near the surface, under the influence of the surface mixed layer. The model results solidly indicated significant connectivity between MCEs and shallow coral ecosystems.

scholarly journals Quasigeostrophic Diagnosis of Mixed Layer Dynamics Embedded in a Mesoscale Turbulent Field

2016 ◽  
Vol 46 (1) ◽  
pp. 275-287 ◽  
Author(s):  
Cédric P. Chavanne ◽  
Patrice Klein
Keyword(s):  
Surface Layer ◽  
High Resolution ◽  
Mixed Layer ◽  
Finite Thickness ◽  
Vertical Mixing ◽  
Three Dimensional ◽  
Upper Ocean ◽  
Surface Mixed Layer ◽  
Deep Interior ◽  
Quasigeostrophic Model

AbstractA quasigeostrophic model is developed to diagnose the three-dimensional circulation, including the vertical velocity, in the upper ocean from high-resolution observations of sea surface height and buoyancy. The formulation for the adiabatic component departs from the classical surface quasigeostrophic framework considered before since it takes into account the stratification within the surface mixed layer that is usually much weaker than that in the ocean interior. To achieve this, the model approximates the ocean with two constant stratification layers: a finite-thickness surface layer (or the mixed layer) and an infinitely deep interior layer. It is shown that the leading-order adiabatic circulation is entirely determined if both the surface streamfunction and buoyancy anomalies are considered. The surface layer further includes a diabatic dynamical contribution. Parameterization of diabatic vertical velocities is based on their restoring impacts of the thermal wind balance that is perturbed by turbulent vertical mixing of momentum and buoyancy. The model skill in reproducing the three-dimensional circulation in the upper ocean from surface data is checked against the output of a high-resolution primitive equation numerical simulation.

scholarly journals Large Reemergence of Anthropogenic Carbon into the Ocean’s Surface Mixed Layer Sustained by the Ocean’s Overturning Circulation

2017 ◽  
Vol 30 (21) ◽  
pp. 8615-8631 ◽  
Author(s):  
Katsuya Toyama ◽  
Keith B. Rodgers ◽  
Bruno Blanke ◽  
Daniele Iudicone ◽  
Masao Ishii ◽  
...  
Keyword(s):  
Gas Exchange ◽  
Ocean Circulation ◽  
Mixed Layer ◽  
World Ocean ◽  
Diagnostic Tools ◽  
Water Volume ◽  
Surface Mixed Layer ◽  
Overturning Circulation ◽  
Carbon Cycle Model ◽  
Anthropogenic Carbon

We evaluate the output from a widely used ocean carbon cycle model to identify the subduction and obduction (reemergence) rates of anthropogenic carbon (Cant) for climatological conditions during the World Ocean Circulation Experiment (WOCE) era in 1995 using a new set of Lagrangian diagnostic tools. The principal scientific value of the Lagrangian diagnostics is in providing a new means to connect Cant reemergence pathways to the relatively rapid renewal time scales of mode waters through the overturning circulation. Our main finding is that for this model with 2.04 PgC yr−1 of uptake of Cant via gas exchange, the subduction and obduction rates across the base of the mixed layer (MLbase) are 4.96 and 4.50 PgC yr−1, respectively, which are twice as large as the gas exchange at the surface. Given that there is net accumulation of 0.17 PgC yr−1 in the mixed layer itself, this implies the residual downward Cant transport of 1.40 PgC yr−1 across the MLbase is associated with diffusion. Importantly, the net patterns for subduction and obduction transports of Cant mirror the large-scale patterns for transport of water volume, thereby illustrating the processes controlling Cant uptake. Although the net transfer across the MLbase by compensating subduction and obduction is relatively smaller than the diffusion, the localized pattern of Cant subduction and obduction implies significant regional impacts. The median time scale for reemergence of obducting particles is short (<10 yr), indicating that reemergence should contribute to limiting future carbon uptake through its contribution to perturbing the Revelle factor for surface waters.

Characteristics and variability of ocean ventilation in the high-latitude North Atlantic in an eddy-permitting ocean model

2021 ◽  
Author(s):  
Helen L. Johnson ◽  
Graeme MacGilchrist ◽  
David P. Marshall ◽  
Camille Lique ◽  
Matthew Thomas ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Mixed Layer ◽  
North Atlantic ◽  
High Latitude ◽  
Circulation Model ◽  
Open Ocean ◽  
Labrador Sea ◽  
Surface Mixed Layer ◽  
Atmospheric Forcing ◽  
Boundary Current

&lt;p&gt;A substantial fraction of the deep ocean is ventilated in the high latitude North Atlantic. As a result, the region plays a crucial role in transient climate change through the uptake of carbon dioxide and heat. We investigate the nature of ventilation in the high latitude North Atlantic in an eddy-permitting numerical ocean circulation model using a set of comprehensive Lagrangian trajectory experiments. Backwards-in-time trajectories from a model-defined &amp;#8216;North Atlantic Deep Water&amp;#8217; (NADW) reveal the times and locations of subduction from the surface mixed layer at high temporal and spatial resolution. The major fraction (&amp;#8764;60%) of NADW ventilation results from subduction directly into the Labrador Sea boundary current, with a smaller fraction (&amp;#8764;25%) arising from open ocean deep convection in the Labrador Sea. There is a notable absence of ventilation arising from subduction in the Greenland&amp;#8211;Iceland&amp;#8211;Norwegian Seas, due to the re-entrainment of those waters as they move southward. Temporal variability in ventilation arises both from changes in subduction &amp;#8212; driven by large-scale atmospheric forcing &amp;#8212; and from year-to-year changes in the subsurface retention of newly subducted water, the result of an inter-annual equivalent of Stommel&amp;#8217;s mixed layer demon. This interannual demon operates most effectively in the open ocean where newly subducted water is slow to escape its region of subduction. Thus, while subduction in the boundary current dominates NADW ventilation, processes in the open ocean set the variability, mediating the translation of inter-annual variations in atmospheric forcing to the ocean interior.&lt;/p&gt;

scholarly journals Diagnosing Surface Mixed Layer Dynamics from High-Resolution Satellite Observations: Numerical Insights

2013 ◽  
Vol 43 (7) ◽  
pp. 1345-1355 ◽  
Author(s):  
Aurelien L. Ponte ◽  
Patrice Klein ◽  
Xavier Capet ◽  
Pierre-Yves Le Traon ◽  
Bertrand Chapron ◽  
...  
Keyword(s):  
High Resolution ◽  
Mixed Layer ◽  
Vertical Mixing ◽  
Mesoscale Eddy ◽  
Three Dimensional ◽  
Satellite Observations ◽  
Scaling Analysis ◽  
Surface Mixed Layer ◽  
Surface Layers ◽  
Velocity Scale

Abstract High-resolution numerical experiments of ocean mesoscale eddy turbulence show that the wind-driven mixed layer (ML) dynamics affects mesoscale motions in the surface layers at scales lower than O(60 km). At these scales, surface horizontal currents are still coherent to, but weaker than, those derived from sea surface height using geostrophy. Vertical motions, on the other hand, are stronger than those diagnosed using the adiabatic quasigeotrophic (QG) framework. An analytical model, based on a scaling analysis and on simple dynamical arguments, provides a physical understanding and leads to a parameterization of these features in terms of vertical mixing. These results are valid when the wind-driven velocity scale is much smaller than that associated with eddies and the Ekman number (related to the ratio between the Ekman and ML depth) is not small. This suggests that, in these specific situations, three-dimensional ML motions (including the vertical velocity) can be diagnosed from high-resolution satellite observations combined with a climatological knowledge of ML conditions and interior stratification.

THREE-DIMENTIONAL CONNECTIVITY OF CORAL LARVAE IN REEF AREAS ON THE NORTHWEST COAST OF OKINAWA MAIN ISLAND, JAPAN

2021 ◽  
Vol 77 (2) ◽  
pp. I_883-I_888
Author(s):  
Kimika TAKEYASU ◽  
Yusuke UCHIYAMA ◽  
Xu ZHANG ◽  
Kosei MATSUSHITA ◽  
Satoshi MITARAI
Keyword(s):  
Northwest Coast ◽  
Coral Larvae ◽  
Main Island

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 Tracking a Coastal Wave Buoy, Lost from the Southern Coast of Jeju Island, Using Lagrangian Particle Modeling

2021 ◽  
Vol 9 (8) ◽  
pp. 795
Author(s):  
Seongbong Seo ◽  
Young-Gyu Park
Keyword(s):  
Japan Sea ◽  
Jeju Island ◽  
East China ◽  
Northwest Pacific ◽  
Southern Coast ◽  
Lagrangian Particle ◽  
The North ◽  
Particle Modeling ◽  
The Usa ◽  
Tracking Model

A coastal wave buoy was lost near Jeju Island, Korea, in late July 2014 and found at Cape Mendocino, USA, in April 2020. The buoy’s journey was simulated with a Lagrangian particle tracking model using surface ocean currents and wind data at 10 m above sea level. Experiments were conducted with windage values of 0, 2, and 4%. Particles were released along the southern coast of Jeju Island from 31 July to 8 August 2014. When the windage was 0 or 2%, most particles reached the northwest Pacific via the East/Japan Sea or East China Sea, respectively. With 4% windage, very few particles entered the North Pacific. Under 0% windage, particles accumulated in the Great Pacific Garbage Patch (GPGP) and never reached the USA. Under 2%, particles were able to escape the GPGP and started to reach the USA coast 2 years and 7 months after the release. The trajectory of the buoy was deduced from the trajectories of particles with a similar travel time. The buoy likely moved to East China and then to the subtropical convergence zone, where it must have circulated for approximately 2 years before being pushed toward Cape Mendocino by the intensified winter westerlies.

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.

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