scholarly journals Behaviorally Mediated Larval Transport in Upwelling Systems

2014 ◽  
Vol 2014 ◽  
pp. 1-17 ◽  
Author(s):  
Steven G. Morgan
Keyword(s):  
Continental Shelf ◽  
Numerical Models ◽  
Tidal Flow ◽  
Population Connectivity ◽  
Larval Transport ◽  
Low Flow ◽  
Surface Currents ◽  
Larval Habitats ◽  
Complete Development ◽  
Interspecific Differences

Highly advective upwelling systems along the western margins of continents are widely believed to transport larvae far offshore in surface currents resulting in larval wastage, limited recruitment, and increased population connectivity. However, suites of larval behaviors effectively mediate interspecific differences in the extent of cross-shelf migrations between nearshore adult habitats and offshore larval habitats. Interspecific differences in behavior determining whether larvae complete development in estuaries or migrate to the continental shelf are evident in large estuaries, but they sometimes may be disrupted by turbulent tidal flow or the absence of a low-salinity cue in shallow, low-flow estuaries, which are widespread in upwelling systems. Larvae of most species on the continental shelf complete development in the coastal boundary layer of reduced flow, whereas other species migrate to the mid- or outer shelf depending on how much time is spent in surface currents. These migrations are maintained across latitudinal differences in the strength and persistence of upwelling, in upwelling jets at headlands, over upwelling-relaxation cycles, and among years of varying upwelling intensity. Incorporating larval behaviors into numerical models demonstrates that larvae recruit closer to home and in higher numbers than when larvae disperse passively or remain in surface currents.

The Pelagic Phase of Spiny Lobster Development

1986 ◽  
Vol 43 (11) ◽  
pp. 2153-2163 ◽  
Author(s):  
B. F. Phillips ◽  
P. S. McWilliam
Keyword(s):  
Continental Shelf ◽  
Ocean Circulation ◽  
General Circulation ◽  
Spiny Lobster ◽  
Water Layer ◽  
Larval Transport ◽  
Surface Currents ◽  
Ontogenetic Changes ◽  
Larval Recruitment ◽  
Phyllosoma Larvae

A reappraisal of the pelagic phase of development in palinurid lobsters, in conjunction with recent oceanographic data, shows that the ontogenetic changes in the vertical migratory behaviour of phyllosoma larvae operate as a biological strategy to effect larval recruitment. Wind-driven surface currents can transport the larvae in the opposite direction to the general circulation of the upper 300 m water layer. Ocean circulation charts are unreliable indicators of likely paths of larval transport because of their gross scale, lack of seasonal information, and the absence of indications of wind-driven surface currents. The majority of larvae are transported beyond the continental shelf to areas greater than 100 km offshore. This appears to be the principal source of larval recruitment to benthic populations, although some local recruitment from coastal areas may occur. Larval transport between populations of Jasus sp. in the Southern Ocean appears likely but is unconfirmed. For some insular populations this may be the sole, or major, source of recruitment. Delayed development of phyllosomata, or of pueruli, may account for year-round settlement in some species. Salinity changes are implicated as a factor stimulating metamorphosis from the final phyllosoma larval stage. The pelagic phase is completed by the nektonic, puerulus stage which swims (possibly directionally) across the continental shelf before settling and metamorphosing into the benthic stage.

Larval Transport in the Coastal Zone: Biological and Physical Processes

2018 ◽  
Keyword(s):  
Simulation Models ◽  
Population Connectivity ◽  
Larval Transport ◽  
Larval Abundance ◽  
Transport Mechanisms ◽  
Larval Behavior ◽  
Physical Processes ◽  
Ecological Processes ◽  
Emergent Technologies ◽  
Advection Diffusion

Larval transport is fundamental to several ecological processes, yet it remains unresolved for the majority of systems. We define larval transport, and describe its components, namely, larval behavior and the physical transport mechanisms accounting for advection, diffusion, and their variability. We then discuss other relevant processes in larval transport, including swimming proficiency, larval duration, accumulation in propagating features, episodic larval transport, and patchiness and spatial variability in larval abundance. We address challenges and recent approaches associated with understanding larval transport, including autonomous sampling, imaging, -omics, and the exponential growth in the use of poorly tested numerical simulation models to examine larval transport and population connectivity. Thus, we discuss the promises and pitfalls of numerical modeling, concluding with recommendations on moving forward, including a need for more process-oriented understanding of the mechanisms of larval transport and the use of emergent technologies.

scholarly journals Stability of a buoyancy-driven coastal current at the shelf break

2002 ◽  
Vol 452 ◽  
pp. 97-121 ◽  
Author(s):  
C. CENEDESE ◽  
P. F. LINDEN
Keyword(s):  
Continental Shelf ◽  
Continental Slope ◽  
Unstable Mode ◽  
Shelf Break ◽  
Coastal Current ◽  
Surface Currents ◽  
Flat Bottom ◽  
Vertical Boundary ◽  
Axisymmetric Disturbances ◽  
A Current

Buoyancy-driven surface currents were generated in the laboratory by releasing buoyant fluid from a source adjacent to a vertical boundary in a rotating container. Different bottom topographies that simulate both a continental slope and a continental ridge were introduced in the container. The topography modified the flow in comparison with the at bottom case where the current grew in width and depth until it became unstable once to non-axisymmetric disturbances. However, when topography was introduced a second instability of the buoyancy-driven current was observed. The most important parameter describing the flow is the ratio of continental shelf width W to the width L* of the current at the onset of the instability. The values of L* for the first instability, and L*−W for the second instability were not influenced by the topography and were 2–6 times the Rossby radius. Thus, the parameter describing the flow can be expressed as the ratio of the width of the continental shelf to the Rossby radius. When this ratio is larger than 2–6 the second instability was observed on the current front. A continental ridge allowed the disturbance to grow to larger amplitude with formation of eddies and fronts, while a gentle continental slope reduced the growth rate and amplitude of the most unstable mode, when compared to the continental ridge topography. When present, eddies did not separate from the main current, and remained near the shelf break. On the other hand, for the largest values of the Rossby radius the first instability was suppressed and the flow was observed to remain stable. A small but significant variation was found in the wavelength of the first instability, which was smaller for a current over topography than over a flat bottom.

scholarly journals Estimation of Coastal Currents Using a Soft Computing Method: A Case Study in Galway Bay, Ireland

2019 ◽  
Vol 7 (5) ◽  
pp. 157 ◽  
Author(s):  
Lei Ren ◽  
Jianming Miao ◽  
Yulong Li ◽  
Xiangxin Luo ◽  
Junxue Li ◽  
...  
Keyword(s):  
Numerical Model ◽  
Soft Computing ◽  
Initial Conditions ◽  
Numerical Models ◽  
Surface Velocity ◽  
Training Dataset ◽  
Model Parameters ◽  
Surface Currents ◽  
Coastal Currents ◽  
Computing Models

In order to obtain forward states of coastal currents, numerical models are a commonly used approach. However, the accurate definition of initial conditions, boundary conditions and other model parameters are challenging. In this paper, a novel application of a soft computing approach, random forests (RF), was adopted to estimate surface currents for three analysis points in Galway Bay, Ireland. Outputs from a numerical model and observations from a high frequency radar system were used as inputs to develop soft computing models. The input variable structure of soft computing models was examined in detail through sensitivity experiments. High correlation of surface currents between predictions from RF models and radar data indicated that the RF algorithm is a most promising means of generating satisfactory surface currents over a long prediction period. Furthermore, training dataset lengths were examined to investigate influences on prediction accuracy. The largest improvement for zonal and meridional surface velocity components over a 59-h forecasting period was 14% and 37% of root mean square error (RMSE) values separately. Results indicate that the combination of RF models with a numerical model can significantly improve forecasting accuracy for surface currents, especially for the meridional surface velocity component.

scholarly journals Data-Driven, Multi-Model Workflow Suggests Strong Influence from Hurricanes on the Generation of Turbidity Currents in the Gulf of Mexico

2020 ◽  
Vol 8 (8) ◽  
pp. 586
Author(s):  
Courtney Harris ◽  
Jaia Syvitski ◽  
H.G. Arango ◽  
E.H. Meiburg ◽  
Sagy Cohen ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Continental Shelf ◽  
Numerical Models ◽  
Ocean Dynamics ◽  
Turbidity Currents ◽  
Regional Ocean Modeling System ◽  
Transport Pathway ◽  
Seabed Sediment ◽  
Continental Scale ◽  
Sediment Routing

Turbidity currents deliver sediment rapidly from the continental shelf to the slope and beyond; and can be triggered by processes such as shelf resuspension during oceanic storms; mass failure of slope deposits due to sediment- and wave-pressure loadings; and localized events that grow into sustained currents via self-amplifying ignition. Because these operate over multiple spatial and temporal scales, ranging from the eddy-scale to continental-scale; coupled numerical models that represent the full transport pathway have proved elusive though individual models have been developed to describe each of these processes. Toward a more holistic tool, a numerical workflow was developed to address pathways for sediment routing from terrestrial and coastal sources, across the continental shelf and ultimately down continental slope canyons of the northern Gulf of Mexico, where offshore infrastructure is susceptible to damage by turbidity currents. Workflow components included: (1) a calibrated simulator for fluvial discharge (Water Balance Model - Sediment; WBMsed); (2) domain grids for seabed sediment textures (dbSEABED); bathymetry, and channelization; (3) a simulator for ocean dynamics and resuspension (the Regional Ocean Modeling System; ROMS); (4) A simulator (HurriSlip) of seafloor failure and flow ignition; and (5) A Reynolds-averaged Navier–Stokes (RANS) turbidity current model (TURBINS). Model simulations explored physical oceanic conditions that might generate turbidity currents, and allowed the workflow to be tested for a year that included two hurricanes. Results showed that extreme storms were especially effective at delivering sediment from coastal source areas to the deep sea, at timescales that ranged from individual wave events (~hours), to the settling lag of fine sediment (~days).

scholarly journals A Simple Parameterization of Turbulent Tidal Mixing near Supercritical Topography

2010 ◽  
Vol 40 (9) ◽  
pp. 2059-2074 ◽  
Author(s):  
Jody M. Klymak ◽  
Sonya Legg ◽  
Robert Pinkel
Keyword(s):  
Internal Wave ◽  
Water Column ◽  
Numerical Models ◽  
Tidal Flow ◽  
Internal Tides ◽  
Tidal Mixing ◽  
Knife Edge ◽  
Wave Interactions ◽  
Tidal Dissipation ◽  
Midocean Ridges

Abstract A simple parameterization for tidal dissipation near supercritical topography, designed to be applied at deep midocean ridges, is presented. In this parameterization, radiation of internal tides is quantified using a linear knife-edge model. Vertical internal wave modes that have nonrotating phase speeds slower than the tidal advection speed are assumed to dissipate locally, primarily because of hydraulic effects near the ridge crest. Evidence for high modes being dissipated is given in idealized numerical models of tidal flow over a Gaussian ridge. These idealized models also give guidance for where in the water column the predicted dissipation should be placed. The dissipation recipe holds if the Coriolis frequency f is varied, as long as hN/W ≫ f, where N is the stratification, h is the topographic height, and W is a width scale. This parameterization is not applicable to shallower topography, which has significantly more dissipation because near-critical processes dominate the observed turbulence. The parameterization compares well against simulations of tidal dissipation at the Kauai ridge but predicts less dissipation than estimated from observations of the full Hawaiian ridge, perhaps because of unparameterized wave–wave interactions.

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