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Dispersion of deep-sea hydrothermal vent effluents and larvae by submesoscale and tidal currents

Dispersion of deep-sea hydrothermal vent effluents and larvae by submesoscale and tidal currents
Dispersion of deep-sea hydrothermal vent effluents and larvae by submesoscale and tidal currents
Deep-sea hydrothermal vents provide sources of geochemical materials that impact the global ocean heat and chemical budgets, and support complex biological communities. Vent effluents and larvae are dispersed and transported long distances by deep ocean currents, but these currents are largely undersampled and little is known about their variability. Submesoscale (0.1–10 km) currents are known to play an important role for the dispersion of biogeochemical materials in the ocean surface layer, but their impact for the dispersion in the deep ocean is unknown. Here, we use a series of nested regional oceanic numerical simulations with increasing resolution (from View the MathML sourceδx=6km to View the MathML sourceδx=0.75km) to investigate the structure and variability of highly-resolved deep currents over the Mid-Atlantic Ridge (MAR) and their role on the dispersion of the Lucky Strike hydrothermal vent effluents and larvae. We shed light on a submesoscale regime of oceanic turbulence over the MAR at 1500 m depth, contrasting with open-ocean – i.e., far from topographic features – regimes of turbulence, dominated by mesoscales.

Impacts of submesoscale and tidal currents on larval dispersion and connectivity among vent populations are investigated by releasing neutrally buoyant Lagrangian particles at the Lucky Strike hydrothermal vent. Although the absolute dispersion is overall not sensitive to the model resolution, submesoscale currents are found to significantly increase both the horizontal and vertical relative dispersion of particles at O(1-10) km and O(1-10) days, resulting in an increased mixing of the cloud of particles. A fraction of particles are trapped in submesoscale coherent vortices, which enable transport over long time and distances. Tidal currents and internal tides do not significantly impact the horizontal relative dispersion. However, they roughly double the vertical dispersion. Specifically, particles undergo strong tidally-induced mixing close to rough topographic features, which allows them to rise up in the water column and to cross topographic obstacles.

The mesoscale variability controls at first order the connectivity between hydrothermal sites and we do not have long enough simulations to conclude on the connectivity between the different MAR hydrothermal sites. However, our simulations suggest that the connectivity might be increased by submesoscale and tidal currents, which act to spread the cloud of particles and help them cross topographic barriers.
0967-0637
1-51
Vic, Clement
408e7f4a-468f-4139-90a6-3a95228ad758
Gula, Jonathan
ff09d520-0745-45fb-9e04-bc4063818977
Roullet, Guillaume
fc8caaf7-9206-4f56-b4ea-b49262bbc58f
Pradillon, Florence
511e5bff-612b-42b8-8396-517a467e3947
Vic, Clement
408e7f4a-468f-4139-90a6-3a95228ad758
Gula, Jonathan
ff09d520-0745-45fb-9e04-bc4063818977
Roullet, Guillaume
fc8caaf7-9206-4f56-b4ea-b49262bbc58f
Pradillon, Florence
511e5bff-612b-42b8-8396-517a467e3947

Vic, Clement, Gula, Jonathan, Roullet, Guillaume and Pradillon, Florence (2018) Dispersion of deep-sea hydrothermal vent effluents and larvae by submesoscale and tidal currents. Deep Sea Research Part I: Oceanographic Research Papers, 1-51. (doi:10.1016/j.dsr.2018.01.001).

Record type: Article

Abstract

Deep-sea hydrothermal vents provide sources of geochemical materials that impact the global ocean heat and chemical budgets, and support complex biological communities. Vent effluents and larvae are dispersed and transported long distances by deep ocean currents, but these currents are largely undersampled and little is known about their variability. Submesoscale (0.1–10 km) currents are known to play an important role for the dispersion of biogeochemical materials in the ocean surface layer, but their impact for the dispersion in the deep ocean is unknown. Here, we use a series of nested regional oceanic numerical simulations with increasing resolution (from View the MathML sourceδx=6km to View the MathML sourceδx=0.75km) to investigate the structure and variability of highly-resolved deep currents over the Mid-Atlantic Ridge (MAR) and their role on the dispersion of the Lucky Strike hydrothermal vent effluents and larvae. We shed light on a submesoscale regime of oceanic turbulence over the MAR at 1500 m depth, contrasting with open-ocean – i.e., far from topographic features – regimes of turbulence, dominated by mesoscales.

Impacts of submesoscale and tidal currents on larval dispersion and connectivity among vent populations are investigated by releasing neutrally buoyant Lagrangian particles at the Lucky Strike hydrothermal vent. Although the absolute dispersion is overall not sensitive to the model resolution, submesoscale currents are found to significantly increase both the horizontal and vertical relative dispersion of particles at O(1-10) km and O(1-10) days, resulting in an increased mixing of the cloud of particles. A fraction of particles are trapped in submesoscale coherent vortices, which enable transport over long time and distances. Tidal currents and internal tides do not significantly impact the horizontal relative dispersion. However, they roughly double the vertical dispersion. Specifically, particles undergo strong tidally-induced mixing close to rough topographic features, which allows them to rise up in the water column and to cross topographic obstacles.

The mesoscale variability controls at first order the connectivity between hydrothermal sites and we do not have long enough simulations to conclude on the connectivity between the different MAR hydrothermal sites. However, our simulations suggest that the connectivity might be increased by submesoscale and tidal currents, which act to spread the cloud of particles and help them cross topographic barriers.

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Accepted/In Press date: 6 January 2018
e-pub ahead of print date: 12 January 2018

Identifiers

Local EPrints ID: 417147
URI: http://eprints.soton.ac.uk/id/eprint/417147
ISSN: 0967-0637
PURE UUID: 765146ae-639e-464a-8ed4-9e707171acc6

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Date deposited: 22 Jan 2018 17:30
Last modified: 27 Apr 2022 04:17

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Contributors

Author: Clement Vic
Author: Jonathan Gula
Author: Guillaume Roullet
Author: Florence Pradillon

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