The Batchelor spectrum and dissipation in the upper ocean

Dillon, Thomas M.; Caldwell, Douglas R.

doi:10.1029/jc085ic04p01910

Cited by 216 publications

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“…Dissipation rates are generally lower in offshore areas and are unlikely to induce a larval sinking response, even during moderate storms. In winds ഠ15 m s Ϫ1 , dissipation rates at the surface and thermocline reach ϭ 10 Ϫ3 -10 Ϫ2 cm 2 s Ϫ3 (Dillon and Caldwell 1980), but our larvae rarely sank at Յ 10 Ϫ2 cm 2 s Ϫ3 . Although stormy conditions at sea could cause some veligers to sink (Barile et al 1994), we expect that larvae will encounter and respond to strong turbulence primarily in nearshore areas.…”

Section: Discussionmentioning

confidence: 99%

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Sinking behavior of gastropod larvae (Ilyanassa obsoleta) in turbulence

Fuchs

Mullineaux

Solow

2004

Limnology & Oceanography

103

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Larvae of coastal gastropods sink in turbulence and may use nearshore turbulence as an initial settlement cue. Our objective was to quantify the relationship between turbulence and the proportion of sinking larvae for competent mud snail veligers (Ilyanassa obsoleta). We exposed larvae to a range of field-relevant turbulence conditions ( ϭ 8.1 ϫ 10 Ϫ3 to 2.7 ϫ 10 0 cm 2 s Ϫ3 ) in a grid-stirred tank, holding other factors constant. We used a video plankton recorder to record larval movements in still water and in turbulence. Larval trajectories and velocity measurements were extracted using video-image analysis. We also measured turbulent flow velocities independently, using laser Doppler velocimetry. To interpret empirical measurements in terms of larval behavior, we developed a threecomponent, normal mixture model for vertical velocity distributions of larvae in turbulence. The model was fitted to observed larval velocities by maximum likelihood, to estimate the proportions of sinking, hovering, and swimming larvae. Over the range of turbulence intensities found in typical coastal habitats, the proportion of sinking larvae increased exponentially (r 2 ϭ 0.89) with the log of the turbulence dissipation rate. The net mean behavioral velocity of the larvae shifted from positive to negative when the dissipation rate reached ϳ10 Ϫ1 cm 2 s Ϫ3 . By sinking when they enter turbulent, shallow water, competent larvae could improve their chances of settling in favorable coastal habitats.Very little is known about how larval behavior in the plankton affects patterns of larval supply and settlement of benthic invertebrates. Much work has been done to describe larval behavior during the exploration of substrates, when larvae can sometimes select settlement sites over small scales (millimeters to centimeters). Less progress has been made on understanding the behavioral contribution while larvae are transported through the water column to benthic habitats. Under some hydrodynamic conditions, larvae could settle more successfully if they responded to waterborne cues by sinking toward the benthos. If the swimming velocity and gravitational sinking velocity differ by a factor of two or more, behavioral changes can significantly affect larval sink-1 Corresponding author (hfuchs@whoi.edu). AcknowledgmentsY. Yamashita helped collect and culture the larvae. We are grateful to J. Sisson for assistance with LDV measurements and to J. H. Trowbridge for guidance on spectral analysis. B. Raubenheimer and E. A. Terray also gave advice on flow data analysis. We thank C. DiBacco for generously sharing his culturing expertise and supplies, V. R. Starczak for advising us on the experimental design, and S. P. McKenna for introducing us to the turbulence tank. S. M. Gallager provided video equipment, software, and advice on particle tracking.

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Section: Discussionmentioning

confidence: 99%

“…Many larvae settle preferentially on particular sediments (Snel- Dillon and Caldwell (1980) Oakey and Elliott (1982) Nowell (1985) George et al (1994) Fig. 1.…”

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confidence: 99%

Sinking behavior of gastropod larvae (Ilyanassa obsoleta) in turbulence

Fuchs

Mullineaux

Solow

2004

Limnology & Oceanography

103

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“…K ρ is ill defined in the absence of stratification and we exclude the segments with N < 1.7×10 −3 s −1 equivalent to one cycle per hour (cph). The eddy diffusivity for heat is obtained from the iso- Osborn and Cox, 1972), using the dissipation rate of thermal variance, (Dillon and Caldwell, 1980), constrained by the measured ε, to the resolved wavenumber band of the T-gradient spectrum over 4 m segments. The noise level for ε is 5−7×10 −10 W kg −1 , only adequate to resolve the turbulence in the upper 200 m, but χ is resolved throughout the profiling depth.…”

Section: Sampling and Processing Detailsmentioning

confidence: 99%

Weak Vertical Diffusion Allows Maintenance of Cold Halocline in the Central Arctic

Fer

2009

Atmospheric and Oceanic Science Letters

120

131

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In spring preceding the record minimum summer ice cover detailed microstructure measurements were made from drifting pack ice in the Arctic Ocean, 110 km from the North Pole. Profiles of hydrography, shear, and temperature microstructure collected in the upper water column covering the core of the Atlantic Water are analyzed to determine the diapycnal eddy diffusivity, the eddy diffusivity for heat, and the turbulent flux of heat. Turbulence in the bulk of the cold halocline layer was not strong enough to generate significant buoyancy flux and mixing. Resulting turbulent heat flux across the upper cold halocline was not significantly different than zero. The results show that the low levels of eddy diffusivity in the upper cold halocline lead to small vertical turbulent transport of heat, thereby allowing the maintenance of the cold halocline in the central Arctic.

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“…It should be noted that this is an indirect inference of turbulence (Thorpe 2005). In a study on marine snow thin layers (Alldredge et al 2002), the turbulent kinetic energy (TKE) dissipation rate, ε, was estimated using the spectra expected for temperature microstructure (Dillon & Caldwell 1980). It was observed that dissipation rate in the thin layer was very low, ε < 10 -8 W kg -1…”

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confidence: 99%

Evolution of the spatial structure of a thin phytoplankton layer into a turbulent field

Wang¹,

Goodman²

2009

Mar. Ecol. Prog. Ser.

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We examined the role of turbulence on the evolution of the spatial structure of a thin phytoplankton layer. The approach used the small autonomous underwater vehicle (AUV), T-REMUS (turbulence-remote environmental measuring units), which is equipped with optical and physical micro-and fine-scale sensors. As part of the Layered Organization in the Coastal Ocean (LOCO) experiment, T-REMUS was deployed in a very shallow region of Monterey Bay, California, USA, over an 8 h nighttime period in summer 2006. A thin layer of chlorophyll a (chl a) was observed throughout the entire experimental period. The center of the thin layer deepened with time, crossed isotherms, and then settled into a strong turbulence layer. This result is in sharp contrast to previous conclusions that biological thin layers only occur in regions of weak turbulence. Our observations indicated that the turbulence field itself was constrained to be in a thin layer by the surrounding strong density stratification. The chl a material, acting as a passive Lagrangian tracer, became embedded within the turbulent field. With time, both the turbulent field and the embedded chl a thin layer were observed to collapse vertically.KEY WORDS: Thin layers · Turbulent mixing · Chlorophyll a · AUV · Monterey Bay · Sinking · Vertical dispersion and contraction Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 374: [57][58][59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74] 2009 rounding local fine-and microstructure physical fields in which the thin layers are embedded.Thin layers have now been observed in a variety of coastal marine environments, including a shallow fjord (East Sound, WA, USA; Alldredge et al. 2002), the continental shelf (Monterey Bay, CA, USA; McManus et al. 2005), and an enclosed sea (Baltic Sea; Nielson et al. 1990). Although recent advances in high resolution optical and acoustical sensors have provided evidence of thin layers at multiple coastal ocean sites (McManus et al. 2005), little direct research has occurred on the role of the very smallest scale physical processes on thin layers. One of the principal objectives of the Layered Organization in the Coastal Ocean (LOCO) experiment was to examine this role.Because of the small size of phytoplankton and their limited mobility, turbulence is thought to have a significant effect on their biodynamics and on the behavior of predatory organisms residing nearby (Donaghay & Osborn 1997, Osborn 1998. Laboratory studies have shown that turbulence can change the size and growth rate of phytoplankton (Sullivan & Swift 2003), change the density of local nutrients and wastes around them (Lazier & Mann 1989), and increase or decrease plankton encounter rates with nutrients (Rothschild & Osborn 1988, Seuront et al. 2001. A recent study by Stacey et al. (2007) employed a model of thin layer formation and maintenance dynamics. In their model, they examined the evolution of biological particles within thin layers in terms of a balanc...

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The Batchelor spectrum and dissipation in the upper ocean

Cited by 216 publications

References 20 publications

Sinking behavior of gastropod larvae (Ilyanassa obsoleta) in turbulence

Sinking behavior of gastropod larvae (Ilyanassa obsoleta) in turbulence

Weak Vertical Diffusion Allows Maintenance of Cold Halocline in the Central Arctic

Evolution of the spatial structure of a thin phytoplankton layer into a turbulent field

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