Preprints
https://doi.org/10.5194/bg-2020-342
https://doi.org/10.5194/bg-2020-342

  30 Sep 2020

30 Sep 2020

Review status: a revised version of this preprint was accepted for the journal BG and is expected to appear here in due course.

Carbon Export and Fate Beneath a Dynamic Upwelled Filament off the California Coast

Hannah L. Bourne1, James K. B. Bishop1,2, Elizabeth J. Connors1,3, and Todd J. Wood2 Hannah L. Bourne et al.
  • 1Dept. of Earth and Planetary Science, University of California, Berkeley, CA, 94720, USA
  • 2Earth and Environmental Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
  • 3Scripps Institution of Oceanography, La Jolla, CA, 92093, USA

Abstract. To understand the vertical variations of carbon fluxes in biologically productive waters, four autonomous Carbon Flux Explorers (CFEs) and ship-lowered CTD-interfaced particle-sensitive transmissometer and scattering sensors were deployed in a filament of offshore flowing recently upwelled water during the June 2017 California Current Ecosystem – Long Term Ecological Research process study. The Lagrangian CFEs operating at depths from 100–500 m yielded carbon flux and its partitioning with size from 30 µm–1 cm at three intense study locations within the filament and at a location outside the filament. Different particle classes (anchovy pellets, copepod pellets and > 1000 µm aggregates) dominated the 100–150 m fluxes during successive stages of the filament evolution as it progressed offshore. Fluxes were very high at all locations in the filament; below 150 m, flux was invariant or increased with depth at the two locations closer to the coast. Martin curve b factors for total particulate carbon flux were +0.1, +0.87, −0.27, and −0.39 at the three successively occupied locations within the plume, and in transitional waters, respectively. Particle transfer efficiencies between 100 to 500 m were far greater within both filament and California Current waters than calculated using a classic Martin b factor of −0.86. Interestingly, the flux profiles for all particles < 400 µm were a much closer fit to Martin; however, most (typically > 90 %) of particle flux was carried by > 1000 µm sized aggregates. Mechanisms to explain a factor of three flux increase between 150 and 500 m at the mid plume location are investigated.

Hannah L. Bourne et al.

 
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Status: closed
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Hannah L. Bourne et al.

Data sets

Original transmitted-light imagery and processed attenuance images of sinking particles observed by autonomous Carbon Flux Explorers deployed 100-500m in the California Current Regime, during the CCE-LTER process study (P1706) between June 2 and July 1, 2 James K. B. Bishop https://doi.org/10.26008/1912/bco-dmo.825076.1

Size fractionated Particulate Carbon Flux 100–500m measured by autonomous Carbon Flux Explorers deployed during the CCE-LTER process study (P1706) between June 2 and July 1, 2017 in the California Current Regime James K. B. Bishop https://doi.org/10.26008/1912/bco-dmo.823408.1

Hannah L. Bourne et al.

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Short summary
To learn how the biological carbon pump works in productive coastal upwelling systems, four autonomous Carbon Flux Explorers measured carbon flux through the twilight zone beneath an offshore-flowing filament of biologically productive water. Strikingly different particle classes dominated the carbon fluxes during successive stages of the filament evolution over 30 days. Both flux and transfer efficiency were far greater than expected suggesting an out-sized filament impact in California waters.
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