Relative Dispersion of Surface Drifters in the North Sea: The Effect of Tides on Mesoscale Diffusivity

Meyerjürgens, Jens; Ricker, Marcel; Schakau, Vanessa; Badewien, Thomas H.; Stanev, Emil V.

doi:10.1029/2019jc015925

Cited by 26 publications

(12 citation statements)

References 89 publications

(184 reference statements)

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“…4). This numerical result is consistent with the analysis of observations presented in [48]. Comparisons with the data from AMM7 and AMM15 (not shown here) demonstrate that the frequency spectra are almost the same in the four models.…”

Section: Eddy Dynamics On the Shelf Continental Slope And Deep Oceansupporting

confidence: 91%

Numerical Eddy-Resolving Modeling of the Ocean: Mesoscale and Sub-Mesoscale Examples

Stanev

Ricker

Grayek

et al. 2020

PhO

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The study addresses rotational motion of geophysical fluids in the horizontal and vertical planes. It is aimed mainly at tracing the development of high-resolution numerical modeling of the ocean, as well as at demonstrating new physical processes due to more correct consideration both of the tides in the eddy-resolving numerical models and sub-mesoscale dynamics in the models of the sea straits. Methods and Results. The ocean eddies and their interaction with tides are studied using numerical simulations by four NEMO models for the European NorthWest shelf with the resolutions ranging from 7 to 1.5 km. The vertical characteristics of motion in the Bosporus Strait were studied using numerical simulations with SCHISM, the unstructured grid model with the ultra-fine model resolution (less than 100 m). The barotropic tidal forcing resulted in substantial flattening of the slopes of the spectral curves. The most important difference between the spectral features of four models occurs in the motion rotational component. In the model with the 1.5 km resolution, the magnitude of the vorticity power spectral density at the scales ~ 70 km is by an order of magnitude higher than in the other three models. Although most of the tidal flattening is associated with the internal tides, beyond a certain horizontal resolution, the eddy dynamics become affected by the barotropic tides. The shelf of the Biscay Bay and the shallows around the Faroe Islands are the most sensitive areas to adding of the barotropic tides to the model forcing. Due to the grid ultra-fine resolution, new elements of physical motion emerged in the Bosporus region. The lateral circulation is dominated by the systems of multiple circulation cells with the scales ~ 1 km. In some areas, the lateral flow magnitude exceeds 0.5 m/s, which is comparable with the magnitude of the axial flow. This reveals importance of the helical elements of the strait circulation for overturning of water masses in the Bosporus. Conclusions. Without proper resolution, the models of tidal oceanic dynamics simulate the ocean general circulation, but do not describe correctly the energy cascades at the eddy scales including interaction between the tides and the mesoscale eddies. Absence of this sub-mesoscale dynamics in the models can largely affect their capability to simulate the two-layer inter-basin exchange.

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Section: Eddy Dynamics On the Shelf Continental Slope And Deep Oceansupporting

confidence: 91%

Numerical Eddy-Resolving Modeling of the Ocean: Mesoscale and Sub-Mesoscale Examples

Stanev

Ricker

Grayek

et al. 2020

PhO

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“…In previous work on drifter dispersion (e.g., Lumpkin and Elipot, 2010;Poje et al, 2014;van Sebille et al, 2015;Meyerjürgens et al, 2020), different scaling regimes have been identified in the FSLE analysis: A Richardson regime predicted by Surface Quasi-Geostrophic (SQG) theory where λ ∝ D −2/3 (Held et al, 1995), an exponential regime predicted by Quasi-Geostrophic (QG) theory where λ is constant (e.g., Pedlosky, 1996), and a diffusive regime where λ ∝ D −2 (LaCasce, 2008).…”

Section: Drifter Pair Separationmentioning

confidence: 99%

Dispersion of Surface Drifters in the Tropical Atlantic

et al. 2021

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The Tropical Atlantic Ocean has recently been the source of enormous amounts of floating Sargassum macroalgae that have started to inundate shorelines in the Caribbean, the western coast of Africa and northern Brazil. It is still unclear, however, how the surface currents carry the Sargassum, largely restricted to the upper meter of the ocean, and whether observed surface drifter trajectories and hydrodynamical ocean models can be used to simulate its pathways. Here, we analyze a dataset of two types of surface drifters (38 in total), purposely deployed in the Tropical Atlantic Ocean in July, 2019. Twenty of the surface drifters were undrogued and reached only ∼8 cm into the water, while the other 18 were standard Surface Velocity Program (SVP) drifters that all had a drogue centered around 15 m depth. We show that the undrogued drifters separate more slowly than the drogued SVP drifters, likely because of the suppressed turbulence due to convergence in wind rows, which was stronger right at the surface than at 15 m depth. Undrogued drifters were also more likely to enter the Caribbean Sea. We also show that the novel Surface and Merged Ocean Currents (SMOC) product from the Copernicus Marine Environmental Service (CMEMS) does not clearly simulate one type of drifter better than the other, highlighting the need for further improvements in assimilated hydrodynamic models in the region, for a better understanding and forecasting of Sargassum drift in the Tropical Atlantic.

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“…Turbulent dispersion of floating particles is influenced by sea waves [25,26], tides [27] and circulation [19][20][21][22]. In this study, the role of the upper, intermediate and deep BS coherent structures on the water mass dispersion is investigated.…”

Section: Introductionmentioning

confidence: 99%

Spreading of Lagrangian Particles in the Black Sea: A Comparison between Drifters and a High-Resolution Ocean Model

et al. 2021

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The Lagrangian dispersion statistics of the Black Sea are estimated using satellite-tracked drifters, satellite altimeter data and a high-resolution ocean model. Comparison between the in-situ measurements and the model reveals good agreement in terms of the surface dispersion. The mean sub-basin coherent structures and currents of the Black Sea are well reproduced by the model. Seasonal variability of the dispersion in the upper (15 m), intermediate (150 m) and deep (750 m) layers are discussed with a special focus of the role of sub-basin scale structures and currents on the turbulent dispersion regimes. In terms of the surface relative dispersion, the results show the presence of the three known turbulent exponential, Richardson and diffusive-like regimes. The non-local exponential regime is only detected by the model for scales <10 km, while the local Richardson regime occurs between 10 and 100 km in all cases due to the presence of an inverse energy cascade range, and the diffusive-like regime is well detected for the largest distance by drifters (100–300 km) in winter/spring. Regarding the surface absolute dispersion, it reflects the occurrence of both quasi-ballistic and random-walk regimes at small and large times, respectively, while the two anomalous hyperbolic (5/4) and elliptic (5/3) regimes, which are related to the topology of the Black Sea, are detected at intermediate times. At depth, the signatures of the relative and absolute dispersion regimes shown in the surface layer are still valid in most cases. The absolute dispersion is anisotropic; the zonal component grows faster than the meridional component in any scenario.

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Relative Dispersion of Surface Drifters in the North Sea: The Effect of Tides on Mesoscale Diffusivity

Cited by 26 publications

References 89 publications

Numerical Eddy-Resolving Modeling of the Ocean: Mesoscale and Sub-Mesoscale Examples

Numerical Eddy-Resolving Modeling of the Ocean: Mesoscale and Sub-Mesoscale Examples

Dispersion of Surface Drifters in the Tropical Atlantic

Spreading of Lagrangian Particles in the Black Sea: A Comparison between Drifters and a High-Resolution Ocean Model

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