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Large-scale impacts of submesoscale dynamics on phytoplankton: Local and remote effects

Large-scale impacts of submesoscale dynamics on phytoplankton: Local and remote effects
Large-scale impacts of submesoscale dynamics on phytoplankton: Local and remote effects
The sensitivity of an idealized bio-physical model of seasonally varying subtropical and subpolar gyres to increased horizontal resolution is presented. Switching from mesoscale-resolving (1/9°) to submesoscale-resolving (1/54°) allows the emergence of a denser and more energetic vortex population sustained by submesoscale physics. The experiments display a global decrease in phytoplankton abundance of ?10–20% as the resolution is refined. This result contrasts with previous studies, which suggested that eddy-driven vertical fluxes of nutrients locally boost phytoplankton growth at mid-latitudes in the open ocean. The explanation is that the long-term (50 years) modification of the large-scale, or basin-scale, circulation and distribution of nutrients by submesoscale processes (remote effects), not taken into account by previous studies because of their much shorter time integration, balance the local, small-scale effects. More precisely, dynamical remote effects (involving only the physics) affect the location of the boundary between the two gyres as well as the large-scale mixed-layer depth (MLD) and thermocline depth. Biological remote effects result from the dynamical remote effects that strongly modify the physical–biological interactions at all scales, including at large scales. These biological remote effects involve changes of the nutricline depth. In the mid-latitude subpolar gyre, phytoplankton decrease in abundance at higher resolution is due to the shallower MLD and nutricline, which promote zooplankton grazing; in the subtropical gyre, it is due to deeper MLD and nutricline, which diminishes regenerated production. In addition, remote effects modulate the dynamical supplies of nutrients to the euphotic layer through a combination of changes in mean advection, eddy advection and vertical mixing.
Submesoscale, Large-scale, Phytoplankton, Primary production, Grazing, Nutricline, Thermocline
1463-5003
77-93
Lévy, M.
5b2dc7b6-d8f0-4727-a4c9-44ce78d62ab3
Iovino, D.
1a3e6472-677a-4441-8018-0e06cb05cdfc
Resplandy, L.
2bec08f0-7dc2-4984-8da6-37c66e05fddb
Klein, P.
211057b8-b8ac-496f-bae4-48fd959f80df
Madec, G.
7e2ec04b-896a-4861-b2d0-b74f39d748c2
Tréguier, A.-M.
2550fa7a-9fcd-483d-a470-df5390d9835e
Masson, S.
facf31ca-bea1-4286-9fd2-61ff721f2165
Takahashi, K.
688388ae-ea43-48e0-a27e-e07871bc4915
Lévy, M.
5b2dc7b6-d8f0-4727-a4c9-44ce78d62ab3
Iovino, D.
1a3e6472-677a-4441-8018-0e06cb05cdfc
Resplandy, L.
2bec08f0-7dc2-4984-8da6-37c66e05fddb
Klein, P.
211057b8-b8ac-496f-bae4-48fd959f80df
Madec, G.
7e2ec04b-896a-4861-b2d0-b74f39d748c2
Tréguier, A.-M.
2550fa7a-9fcd-483d-a470-df5390d9835e
Masson, S.
facf31ca-bea1-4286-9fd2-61ff721f2165
Takahashi, K.
688388ae-ea43-48e0-a27e-e07871bc4915

Lévy, M., Iovino, D., Resplandy, L., Klein, P., Madec, G., Tréguier, A.-M., Masson, S. and Takahashi, K. (2012) Large-scale impacts of submesoscale dynamics on phytoplankton: Local and remote effects. Ocean Modelling, 43-44, 77-93. (doi:10.1016/j.ocemod.2011.12.003).

Record type: Article

Abstract

The sensitivity of an idealized bio-physical model of seasonally varying subtropical and subpolar gyres to increased horizontal resolution is presented. Switching from mesoscale-resolving (1/9°) to submesoscale-resolving (1/54°) allows the emergence of a denser and more energetic vortex population sustained by submesoscale physics. The experiments display a global decrease in phytoplankton abundance of ?10–20% as the resolution is refined. This result contrasts with previous studies, which suggested that eddy-driven vertical fluxes of nutrients locally boost phytoplankton growth at mid-latitudes in the open ocean. The explanation is that the long-term (50 years) modification of the large-scale, or basin-scale, circulation and distribution of nutrients by submesoscale processes (remote effects), not taken into account by previous studies because of their much shorter time integration, balance the local, small-scale effects. More precisely, dynamical remote effects (involving only the physics) affect the location of the boundary between the two gyres as well as the large-scale mixed-layer depth (MLD) and thermocline depth. Biological remote effects result from the dynamical remote effects that strongly modify the physical–biological interactions at all scales, including at large scales. These biological remote effects involve changes of the nutricline depth. In the mid-latitude subpolar gyre, phytoplankton decrease in abundance at higher resolution is due to the shallower MLD and nutricline, which promote zooplankton grazing; in the subtropical gyre, it is due to deeper MLD and nutricline, which diminishes regenerated production. In addition, remote effects modulate the dynamical supplies of nutrients to the euphotic layer through a combination of changes in mean advection, eddy advection and vertical mixing.

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More information

Published date: 2012
Keywords: Submesoscale, Large-scale, Phytoplankton, Primary production, Grazing, Nutricline, Thermocline
Organisations: Marine Systems Modelling

Identifiers

Local EPrints ID: 210956
URI: https://eprints.soton.ac.uk/id/eprint/210956
ISSN: 1463-5003
PURE UUID: 8b1feb22-8244-4dc8-9690-b754762db312

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Date deposited: 15 Feb 2012 09:48
Last modified: 18 Jul 2017 10:44

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Contributors

Author: M. Lévy
Author: D. Iovino
Author: L. Resplandy
Author: P. Klein
Author: G. Madec
Author: A.-M. Tréguier
Author: S. Masson
Author: K. Takahashi

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