title: Mesoscale ocean fronts enhance carbon export due to gravitational sinking and subduction.
abstract: Enhanced vertical carbon transport (gravitational sinking and subduction) at mesoscale ocean fronts may explain the demonstrated imbalance of new production and sinking particle export in coastal upwelling ecosystems. Based on flux assessments from238U:234Th disequilibrium and sediment traps, we found 2 to 3 times higher rates of gravitational particle export near a deep-water front (305 mg C⋅m-2⋅d-1) compared with adjacent water or to mean (nonfrontal) regional conditions. Elevated particle flux at the front was mechanistically linked to Fe-stressed diatoms and high mesozooplankton fecal pellet production. Using a data assimilative regional ocean model fit to measured conditions, we estimate that an additional ∼225 mg C⋅m-2⋅d-1was exported as subduction of particle-rich water at the front, highlighting a transport mechanism that is not captured by sediment traps and is poorly quantified by most models and in situ measurements. Mesoscale fronts may be responsible for over a quarter of total organic carbon sequestration in the California Current and other coastal upwelling ecosystems.
authors.affiliation: Earth, Ocean, and Atmospheric Science Department, Florida State University, Tallahassee, FL 32306; mstukel@fsu.edu.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Stukel
authors.affiliation: Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093.
authors.forename: Lihini I
authors.initials: LI
authors.lastname: Aluwihare
authors.affiliation: Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093.
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Barbeau
authors.affiliation: Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964.
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Chekalyuk
authors.affiliation: Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093.
authors.forename: Ralf
authors.initials: R
authors.lastname: Goericke
authors.affiliation: Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093.
authors.forename: Arthur J
authors.initials: AJ
authors.lastname: Miller
authors.affiliation: Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Ohman
authors.affiliation: Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093.
authors.forename: Angel
authors.initials: A
authors.lastname: Ruacho
authors.affiliation: Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139.
authors.forename: Hajoon
authors.initials: H
authors.lastname: Song
authors.affiliation: Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093.
authors.forename: Brandon M
authors.initials: BM
authors.lastname: Stephens
authors.affiliation: Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Landry
keywords: biological carbon pump; carbon cycle; particle flux; particulate organic carbon; plankton