Using a Lagrangian model to estimate source regions of particles in sediment traps

Qiu, Zhongfeng; Doglioli, Andrea M.; Carlotti, François

doi:10.1007/s11430-014-4880-x

Cited by 9 publications

(12 citation statements)

References 32 publications

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“…In this case, what is appropriate is to take the limit defined by St → 0 and Fr → 0 with the value of W ∼ St/Fr 2 remaining constant. Both in this new limit (see Appendix A) and in the standard approach 24 with W ≫ St, the leading order contribution in St to the equation of motion for the particle is a well-known 7,[9][10][11][12] approximation:…”

Section: A Equations Of Motionmentioning

confidence: 99%

“…These inhomogeneities emerge as a result of advection of the particles by flows in the ocean. For the range of parameters that is relevant for marine biogenic particles, a very good approximation for the equation of motion of the particles 7,9,10,12 , as it has been explicitly shown in 11 , simply consists of motion following the fluid velocity with an additional settling term.…”

Section: Introductionmentioning

confidence: 99%

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Inhomogeneities and caustics in the sedimentation of noninertial particles in incompressible flows

Drótos

Monroy

Hernández-Garcı́a

et al. 2019

Chaos: An Interdisciplinary Journal of Nonlinear Science

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In an incompressible flow, fluid density remains invariant along fluid element trajectories. This implies that the spatial distribution of non-interacting noninertial particles in such flows cannot develop density inhomogeneities beyond those that are already introduced in the initial condition. However, in certain practical situations, density is measured or accumulated on (hyper-) surfaces of dimensionality lower than the full dimensionality of the flow in which the particles move. An example is the observation of particle distributions sedimented on the floor of the ocean. In such cases, even if the initial distribution of noninertial particles is uniform within a finite support in an incompressible flow, advection in the flow will give rise to inhomogeneities in the observed density. In this paper we analytically derive, in the framework of an initially homogeneous particle sheet sedimenting towards a bottom surface, the relationship between the geometry of the flow and the emerging distribution. From a physical point of view, we identify the two processes that generate inhomogeneities to be the stretching within the sheet, and the projection of the deformed sheet onto the target surface. We point out that an extreme form of inhomogeneity, caustics, can develop for sheets. We exemplify our geometrical results with simulations of particle advection in a simple kinematic flow, study the dependence on various parameters involved, and illustrate that the basic mechanisms work similarly if the initial (homogeneous) distribution occupies a more general region of finite extension rather than a sheet. a) gabor@ifisc.uib-csic.es 1 Sedimentation of small particles in complex flows is an outstanding problem in science and technology. In particular, the sinking of biogenic particles from the marine surface to the bottom is a fundamental process of the biological carbon pump, playing a key role in the global carbon cycle. A complete understanding of this problem is still lacking. It has been recently shown that despite fluid incompressibility, sedimenting particles moving as noninertial particles in the ocean on large scales show density inhomogeneities when accumulated on some bottom surface. Here, we analytically derive the relation between the geometry of the flow and the emerging distribution for an initially homogeneous sheet of particles. From a physical point of view, we identify the two processes that generate inhomogeneities to be the stretching within the sheet, and the projection of the deformed sheet onto the target surface. We point out conditions under which an extreme form of inhomogeneity, caustics, can develop.

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Section: A Equations Of Motionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Inhomogeneities and caustics in the sedimentation of noninertial particles in incompressible flows

Drótos

Monroy

Hernández-Garcı́a

et al. 2019

Chaos: An Interdisciplinary Journal of Nonlinear Science

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“…Thus, if taking l ∼ 8 km = 8000 m (corresponding to 1/12 • ) we obtain 10m 2 /s. In the vertical direction we use a constant value of D v = 10 −5 m 2 /s (Rossi et al, 2013).…”

Section: Numerical Simulationsmentioning

confidence: 99%

“…This is a challenging task that involves the downward transport of particles of many different sizes and densities by turbulent ocean flows which contain an enormous range of interacting scales. In the oceanographic community, numerous studies approached this problem by considering biogenic particles transported in oceanic flow as passive particles with an added constant velocity in the vertical to account for the sinking dynamics (Siegel and Deuser, 1997;Siegel et al, 2008;Qiu et al, 2014;Roullier et al, 2014;van Sebille et al, 2015). They suggest that the sinking of particles may not be strictly vertical but oblique, meaning that the locations where the particles are formed at the surface may be distant from the location of their deposition in the seafloor sediment.…”

Section: Introductionmentioning

confidence: 99%

Modeling the dynamical sinking of biogenic particles in oceanic flow

Monroy

Hernández-Garcı́a

Rossi

et al. 2017

Nonlin. Processes Geophys.

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Abstract. We study the problem of sinking particles in a realistic oceanic flow, with major energetic structures in the mesoscale, focussing on the range of particle sizes and densities appropriate for marine biogenic particles. Our aim is to evaluate the relevance of theoretical results of finite size particle dynamics in their applications in the oceanographic context. By using a simplified equation of motion of small particles in a mesoscale simulation of the oceanic velocity field, we estimate the influence of physical processes such as the Coriolis force and the inertia of the particles, and we conclude that they represent negligible corrections to the most important terms, which are passive motion with the velocity of the flow, and a constant added vertical velocity due to gravity. Even if within this approximation three-dimensional clustering of particles can not occur, two-dimensional cuts or projections of the evolving three-dimensional density can display inhomogeneities similar to the ones observed in sinking ocean particles.

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“…At the end of their life cycle-during the phase of gametogenesis-foraminifera lose their ability to stay buoyant in the upper ocean and their shells sink to the ocean floor to become part of the sedimentary geological archive [1][2][3][4][5]8 . Although the horizontal advection distance for post-mortem sinking foraminifera has been estimated at a few hundred kilometres 6,[9][10][11][12] , there is a remarkable dearth of information on the geographical footprint of foraminifera during their lifespan.…”

mentioning

confidence: 99%

Ocean currents generate large footprints in marine palaeoclimate proxies

et al. 2015

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Fossils of marine microorganisms such as planktic foraminifera are among the cornerstones of palaeoclimatological studies. It is often assumed that the proxies derived from their shells represent ocean conditions above the location where they were deposited. Planktic foraminifera, however, are carried by ocean currents and, depending on the life traits of the species, potentially incorporate distant ocean conditions. Here we use high-resolution ocean models to assess the footprint of planktic foraminifera and validate our method with proxy analyses from two locations. Results show that foraminifera, and thus recorded palaeoclimatic conditions, may originate from areas up to several thousands of kilometres away, reflecting an ocean state significantly different from the core site. In the eastern equatorial regions and the western boundary current extensions, the offset may reach 1.5°C for species living for a month and 3.0°C for longer-living species. Oceanic transport hence appears to be a crucial aspect in the interpretation of proxy signals.

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Using a Lagrangian model to estimate source regions of particles in sediment traps

Abstract: International audienc

Cited by 9 publications

References 32 publications

Inhomogeneities and caustics in the sedimentation of noninertial particles in incompressible flows

Inhomogeneities and caustics in the sedimentation of noninertial particles in incompressible flows

Modeling the dynamical sinking of biogenic particles in oceanic flow

Ocean currents generate large footprints in marine palaeoclimate proxies

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