Estimates of vertical turbulent mixing used to determine a vertical gradient in net and gross oxygen production in the oligotrophic South Pacific Gyre uri icon

abstract

  • AbstractMixed layer (ML) gross (GOP) and net (NOP) oxygen production rates based on in situ mass balances of triple oxygen isotopes (TOI) and O2/Ar are influenced by vertical transport from below, a term traditionally difficult to constrain. Here we present a new approach to estimate vertical eddy diffusivity (Kz) based on density gradients in the upper thermocline and wind speedbased rates of turbulent shear at the ML depth. As an example, we use this Kz, verified by an independent 7Bebased estimate, in an O2/TOI budget at a site in the oligotrophic South Pacific Gyre. NOP equaled 0.310.16mmolm2d1 in the ML (~5565m depth) and 1.20.4mmolm2d1 (80%) beneath the ML, while GOP equaled 7427mmolm2d1 (86%) in the ML and 124mmolm2d1 (14%) below, revealing a vertical gradient in production rates unquantifiable without the Kz estimate.

published proceedings

  • Geophysical Research Letters

author list (cited authors)

  • Haskell, W. Z., Prokopenko, M. G., Stanley, R., & Knapp, A. N.

complete list of authors

  • Haskell, WZ||Prokopenko, MG||Stanley, RHR||Knapp, AN