Biological production in the Indian Ocean upwelling zones –Part 1: refined estimation via the use of a variable compensation depth in ocean carbon models
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Published:2018-04-03
Issue:7
Volume:15
Page:1895-1918
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ISSN:1726-4189
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Container-title:Biogeosciences
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language:en
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Short-container-title:Biogeosciences
Author:
Sreeush Mohanan Geethalekshmi, Valsala Vinu, Pentakota SreenivasORCID, Prasad Koneru Venkata Siva Rama, Murtugudde Raghu
Abstract
Abstract. Biological modelling approach adopted by the Ocean Carbon-Cycle Model
Intercomparison Project (OCMIP-II) provided amazingly simple but
surprisingly accurate rendition of the annual mean carbon cycle for the
global ocean. Nonetheless, OCMIP models are known to have seasonal biases
which are typically attributed to their bulk parameterisation of
compensation depth. Utilising the criteria of surface Chl a-based
attenuation of solar radiation and the minimum solar radiation required for
production, we have proposed a new parameterisation for a spatially and
temporally varying compensation depth which captures the seasonality in
the production zone reasonably well. This new parameterisation is shown to
improve the seasonality of CO2 fluxes, surface ocean pCO2,
biological export and new production in the major upwelling zones of the
Indian Ocean. The seasonally varying compensation depth enriches the nutrient
concentration in the upper ocean yielding more faithful biological exports
which in turn leads to accurate seasonality in the carbon cycle. The
export production strengthens by ∼ 70 % over the western Arabian Sea
during the monsoon period and achieves a good balance between export and new
production in the model. This underscores the importance of having a seasonal
balance in the model export and new productions for a better representation of
the seasonality of the carbon cycle over upwelling regions. The study also
implies that both the biological and solubility pumps play an important role
in the Indian Ocean upwelling zones.
Publisher
Copernicus GmbH
Subject
Earth-Surface Processes,Ecology, Evolution, Behavior and Systematics
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