Electronic versions


  • 2019GB006214

    Accepted author manuscript, 1 MB, PDF-document

    Embargo ends: 1/02/20


  • Robyn Tuerena
  • Ric Williams
  • Claire Mahaffey
    Liverpool University
  • Mattias Green
  • Clement Vic
    National Oceanography Centre, Southampton
  • Alberto Naveira-Garabato
    National Oceanography Centre, Southampton
  • Alex Forryan
    National Oceanography Centre, Southampton
  • Jonathan Sharples
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 enhances 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 eight 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
Original languageEnglish
JournalGlobal Biogeochemical Cycles
Early online date1 Aug 2019
Publication statusE-pub ahead of print - 1 Aug 2019
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