Internal Tides Drive Nutrient Fluxes Into the Deep Chlorophyll Maximum Over Mid‐ocean Ridges

Tuerena, R, Williams, R ORCID: 0000-0002-3180-7558, Mahaffey, C ORCID: 0000-0002-4215-7271, Clément Vic, J, Green, M, Naveira‐Garabato, A, Forryan, A and Sharples, J ORCID: 0000-0002-7031-3593 (2019) Internal Tides Drive Nutrient Fluxes Into the Deep Chlorophyll Maximum Over Mid‐ocean Ridges. Global Biogeochemical Cycles: an international journal of global change, 33 (8). pp. 995-1009.

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Abstract

Diapycnal mixing of nutrients from the thermocline to the surface sunlit ocean is thought to be relatively weak in the world's subtropical gyres as energy inputs from winds are generally low. The interaction of internal tides with rough topography enhances diapycnal mixing, yet the role of tidally induced diapycnal mixing in sustaining nutrient supply to the surface subtropical ocean remains relatively unexplored. During a field campaign in the North Atlantic subtropical gyre, we tested whether tidal interactions with topography enhance diapycnal nitrate fluxes in the upper ocean. We measured an order of magnitude increase in diapycnal nitrate fluxes to the deep chlorophyll maximum (DCM) over the Mid‐Atlantic Ridge compared to the adjacent deep ocean. Internal tides drive this enhancement, with diapycnal nitrate supply to the DCM increasing by a factor of 8 between neap and spring tides. Using a global tidal dissipation database, we find that this spring‐neap enhancement in diapycnal nitrate fluxes is widespread over ridges and seamounts. Mid‐ocean ridges therefore play an important role in sustaining the nutrient supply to the DCM, and these findings may have important implications in a warming global ocean.

Item Type:	Article
Uncontrolled Keywords:	mixing, nitrate, tides, nutrients, Atlantic, gyre
Depositing User:	Symplectic Admin
Date Deposited:	02 Sep 2019 09:39
Last Modified:	19 Jan 2023 00:28
DOI:	10.1029/2019GB006214
Open Access URL:	https://doi.org/10.1029/2019GB006214
Related URLs:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3052933