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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2019-289
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-289
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 31 Jul 2019

Submitted as: research article | 31 Jul 2019

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This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).

On modeling the Southern Ocean Phytoplankton Functional Types

Svetlana N. Losa1,2, Stephanie Dutkiewicz3, Martin Losch1, Julia Oelker4, Mariana A. Soppa1, Scarlett Trimborn1, Hongyan Xi1, and Astrid Bracher1,4 Svetlana N. Losa et al.
  • 1Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
  • 2Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia
  • 3Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
  • 4Institute of Environmental Physics (IUP), University of Bremen, Bremen, Germany

Abstract. This study highlights recent advances and challenges of applying coupled physical-biogeochemical modeling for investigating the distribution of the key phytoplankton groups in the Southern Ocean, an area of strong interest for understanding biogeochemical cycling and ecosystem functioning under present climate change. Our simulations of the phenology of various Phytoplankton Functional Types (PFTs) are based on a version of the Darwin biogeochemical model coupled to the Massachusetts Institute of Technology (MIT) general circulation model (Darwin-MITgcm). The ecological module version was adapted for the Southern Ocean by: 1) improving coccolithophores abundance relative to the original model by introducing a high affinity for nutrients and an ability to escape grazing control for coccolithophores; 2) including two different (small vs. large) size classes of diatoms; and 3) accounting for two distinct life stages for Phaeocystis (single cell vs. colonial). This new model configuration describes best the competition and co-occurrence of the PFTs in the Southern Ocean. It improves significantly relative to an older version the agreement of the simulated abundance of the coccolithophores and diatoms with in situ scanning electron microscopy observations in the Subantarctic Zone as well as with in situ diatoms and haptophytes (including coccolithophores and Phaeocystis) chlorophyll a concentrations within the Patagonian Shelf and along the Western Antarctic Peninsula obtained by diagnostic pigment analysis. The modeled Southern Ocean PFT dominance also agrees well with satellite-based PFT information.

Svetlana N. Losa et al.
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Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Svetlana N. Losa et al.
Video supplement

Simulated distribution of diatom chlorophyll concentration in the Southern Ocean S. N. Losa, S. Dutkiewicz, M. Losch, J. Oelker, M. A. Soppa, S. Trimborn, H. Xi, and A. Bracher https://doi.org/10.5446/42871

Simulated distribution of haptophytes chlorophyll concentration in the Southern Ocean S. N. Losa, S. Dutkiewicz, M. Losch, J. Oelker, M. A. Soppa, S. Trimborn, H. Xi, and A. Bracher https://doi.org/10.5446/42873

Simulated distribution of prokaryotes chlorophyll concentration in the Southern Ocean S. N. Losa, S. Dutkiewicz, M. Losch, J. Oelker, M. A. Soppa, S. Trimborn, H. Xi, and A. Bracher https://doi.org/10.5446/42872

Svetlana N. Losa et al.
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Short summary
This study highlights recent advances and challenges of applying coupled physical-biogeochemical modeling for investigating the distribution of the key phytoplankton groups in the Southern Ocean. By leveraging satellite and in situ observations we define numerical ecological model requirements in the phytoplankton trait specification and level of physiological and morphological differentiation for capturing and explaining the observed biogeography of diatoms, coccolithophores and Phaeocystis.
This study highlights recent advances and challenges of applying coupled physical-biogeochemical...
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