Copepod Aggregations: Influences of Physics and Collective Behavior

Abstract

Dense copepod aggregations form in Massachusetts Bay and provide an important resource for right whales. We re-examine the processes which might account for the high concentrations, investigating both horizontally convergent flow, which can increase the density of depth-keeping organisms, and social behavior. We argue that the two act in concert: social behavior creates small dense patches (on the scale of a few sensing radii); physical stirring brings them together so that they merge into aggregations with larger scales; it also moves them into areas of physical convergence which retain the increasingly large patch. But the turbulence can also break this apart, suggesting that the overall high density in the convergence zone will not be uniform but will instead be composed of multiple transient patches (which are still much larger than the sensing scale).

Competition between chaotic advection and diffusion: stirring and mixing in a 3-D eddy model

“…Below we present a simple explanation for the Lagrangian Batchelor scale to gain intuition about this quantity, followed by a rigorous derivation of a Lagrangian Batchelor scale for a Gaussian tracer in a 3-D linear strain flow. The latter extends the work of Flierl and Woods (2015)…”

“…As an alternative motivation of the Lagrangian Batchelor scale, we show analytically that the width of a Gaussian tracer distribution asymptotically approaches the Batchelor scale in a simple flow field. This derivation is an extension to three dimensions of a two-dimensional calculation by Flierl and Woods (2015). The main steps of the derivation are described below, with more details in Appendix B.…”

Chaotic advection, mixing, and property exchange in three-dimensional ocean eddies and gyres

“…First, there is the evolution of a Gaussian tracer distribution in linear three-dimensional flow, updated from a similar derivation by Flierl and Woods (2015). Second, a derivation of the Nakamura effective diffusivity in a constant-density fluid in three dimensions, updated from a two-dimensional presentation by .…”

“…Then can be written as 21) where now stands for a small area on the surface. This form describes integrating a series of shells in for whatever scalar function is chosen.…”

Competition between Chaotic Advection and Diffusion: Stirring and Mixing in a 3D Eddy Model

“…As an alternative motivation of the Lagrangian Batchelor scale, we show analytically that the 325 width of a Gaussian tracer distribution asymptotically approaches the Batchelor scale in a simple flow field. This derivation is an extension to three dimensions of a two-dimensional calculation by Flierl and Woods (2015). The main steps of the derivation are described below, with more details in the Appendix B.…”