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Intense upper ocean mixing due to large aggregations of spawning fish

Intense upper ocean mixing due to large aggregations of spawning fish
Intense upper ocean mixing due to large aggregations of spawning fish
Small-scale turbulent mixing plays a pivotal role in shaping ocean circulation and a broad range of physical and biogeochemical processes. Despite advances in our understanding of the geophysical processes responsible for this mixing, the nature and importance of biomixing—turbulent mixing caused by marine biota—are still debated. A major source of uncertainty pertains to the efficiency of biomixing (the fraction of the turbulent energy produced through swimming that is spent in mixing the ocean vertically), which the few in situ observations available suggest to be much lower than that of geophysical turbulence. Here we shed light on this problem by analysing 14 days of continuous measurements of centimetre-scale turbulence in an area of coastal upwelling. We show that turbulent dissipation is elevated 10- to 100-fold (reaching 10−6–10−5 W kg−1) every night of the survey due to the swimming activity of large aggregations of anchovies that gather regularly over the spawning season. Turbulent mixing is invigorated concurrently with dissipation, and occurs with an efficiency comparable to that of geophysical turbulence. Our results demonstrate that biologically driven turbulence can be a highly effective mixing agent, and call for a re-examination of its impacts on productive upper ocean regions.
1752-0894
287-292
Fernández Castro, Bieito
8017e93c-d5ee-4bba-b443-9c72ca512d61
Peña, Marian
36e6fb09-9e82-4f44-9cf9-b3088ee661ea
Nogueira, Enrique
28843ec2-b3ba-4835-a8ce-53d770b776bc
Gilcoto, Miguel
431de478-8e3a-4e3a-83eb-bd6f27c9a82b
Broullón, Esperanza
f90cfa74-83be-4bed-8ef6-32cc679c1049
Comesaña, Antonio
3c29ae16-3834-4e3b-972c-d417b557b355
Bouffard, Damien
a3eb0e77-974e-40b5-a122-388e1c15704b
Naveira Garabato, Alberto C.
97c0e923-f076-4b38-b89b-938e11cea7a6
Mouriño-carballido, Beatriz
1bfd941d-9ec6-473f-94bd-bb6faac56fa5
Fernández Castro, Bieito
8017e93c-d5ee-4bba-b443-9c72ca512d61
Peña, Marian
36e6fb09-9e82-4f44-9cf9-b3088ee661ea
Nogueira, Enrique
28843ec2-b3ba-4835-a8ce-53d770b776bc
Gilcoto, Miguel
431de478-8e3a-4e3a-83eb-bd6f27c9a82b
Broullón, Esperanza
f90cfa74-83be-4bed-8ef6-32cc679c1049
Comesaña, Antonio
3c29ae16-3834-4e3b-972c-d417b557b355
Bouffard, Damien
a3eb0e77-974e-40b5-a122-388e1c15704b
Naveira Garabato, Alberto C.
97c0e923-f076-4b38-b89b-938e11cea7a6
Mouriño-carballido, Beatriz
1bfd941d-9ec6-473f-94bd-bb6faac56fa5

Fernández Castro, Bieito, Peña, Marian, Nogueira, Enrique, Gilcoto, Miguel, Broullón, Esperanza, Comesaña, Antonio, Bouffard, Damien, Naveira Garabato, Alberto C. and Mouriño-carballido, Beatriz (2022) Intense upper ocean mixing due to large aggregations of spawning fish. Nature Geoscience, 15 (4), 287-292. (doi:10.1038/s41561-022-00916-3).

Record type: Article

Abstract

Small-scale turbulent mixing plays a pivotal role in shaping ocean circulation and a broad range of physical and biogeochemical processes. Despite advances in our understanding of the geophysical processes responsible for this mixing, the nature and importance of biomixing—turbulent mixing caused by marine biota—are still debated. A major source of uncertainty pertains to the efficiency of biomixing (the fraction of the turbulent energy produced through swimming that is spent in mixing the ocean vertically), which the few in situ observations available suggest to be much lower than that of geophysical turbulence. Here we shed light on this problem by analysing 14 days of continuous measurements of centimetre-scale turbulence in an area of coastal upwelling. We show that turbulent dissipation is elevated 10- to 100-fold (reaching 10−6–10−5 W kg−1) every night of the survey due to the swimming activity of large aggregations of anchovies that gather regularly over the spawning season. Turbulent mixing is invigorated concurrently with dissipation, and occurs with an efficiency comparable to that of geophysical turbulence. Our results demonstrate that biologically driven turbulence can be a highly effective mixing agent, and call for a re-examination of its impacts on productive upper ocean regions.

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Accepted/In Press date: 24 February 2022
Published date: 7 April 2022

Identifiers

Local EPrints ID: 457468
URI: http://eprints.soton.ac.uk/id/eprint/457468
ISSN: 1752-0894
PURE UUID: 29d3d2f0-1f97-4122-9c75-b0ae738a2801
ORCID for Bieito Fernández Castro: ORCID iD orcid.org/0000-0001-7797-854X
ORCID for Alberto C. Naveira Garabato: ORCID iD orcid.org/0000-0001-6071-605X

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Date deposited: 09 Jun 2022 16:51
Last modified: 27 Jan 2023 02:39

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Contributors

Author: Marian Peña
Author: Enrique Nogueira
Author: Miguel Gilcoto
Author: Esperanza Broullón
Author: Antonio Comesaña
Author: Damien Bouffard
Author: Beatriz Mouriño-carballido

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