The origin of sub-surface source waters define the sea-air flux of methane in the Mauritanian Upwelling, NW Africa

Brown, IJ; Torres, R; Rees, AP. 2014 The origin of sub-surface source waters define the sea-air flux of methane in the Mauritanian Upwelling, NW Africa. Dynamics of Atmospheres and Oceans. 10.1016/j.dynatmoce.2014.06.001

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Official URL: http://dx.doi.org/10.1016/j.dynatmoce.2014.06.001

Abstract/Summary

Concentrations and flux densities of methane were determined during a lagrangian study of an advective filament in the permanent upwelling region off western Mauritania. Newly upwelled waters were dominated by the presence of North Atlantic Central Water and surface CH4 concentrations of 2.2 ± 0.3 nmol L-1 were largely in equilibrium with atmospheric values, with surface saturations of 101.7 ± 14%. As the upwelling filament aged and was advected offshore, CH4 enriched South Atlantic Central Water from intermediate depths of 100 to 350m was entrained into the surface mixed layer of the filament following intense mixing associated with the shelf break. Surface saturations increased to 198.9 ± 15% and flux densities increased from a mean value over the shelf of 2.0 ± 1.1 µmol m-2d-1 to a maximum of 22.6 µmol m-2d-1. Annual CH4 emissions for this persistent filament were estimated at 0.77 ± 0.64 Gg which equates to a maximum of 0.35% of the global oceanic budget. This raises the known outgassing intensity of this area and highlights the importance of advecting filaments from upwelling waters as efficient vehicles for air-sea exchange.

Item Type: Publication - Article
Additional Keywords: Methane, Atlantic Ocean, Upwelling, Filaments, Air-sea exchange
Subjects: Atmospheric Sciences
Marine Sciences
Oceanography
Divisions: Plymouth Marine Laboratory > Science Areas > Cycling in the Sunlit Ocean
Depositing User: Andy Rees
Date made live: 22 Jul 2014 15:53
Last Modified: 06 Jun 2017 16:12
URI: http://plymsea.ac.uk/id/eprint/6149

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