Optimization of Biological Production for Indian Ocean upwelling zones: Part – I: Improving Biological Parameterization via a variable Compensation Depth

Abstract. Biological modeling approach adopted by the Ocean Carbon Cycle Model Inter-comparison 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 parameterization of compensation depth. Utilizing the principle of minimum solar radiation for the production and its attenuation by the surface Chl-a, we have proposed a new parameterization for a spatially and temporally varying compensation depth which captures the seasonality in the production zone reasonably well. This new parameterization 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 an accurate seasonality in carbon cycle. The export production strengthens by ~ 70 % over western Arabian sea during monsoon period and achieved a good balance between export and new production in the model. This underscores the importance of having a seasonal balance in model export and new production for a better representation of the seasonality of 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.

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Biological production in the Indian Ocean upwelling zones –Part 1: refined estimation via the use of a variable compensation depth in ocean carbon models

Biogeosciences ◽

10.5194/bg-15-1895-2018 ◽

2018 ◽

Vol 15 (7) ◽

pp. 1895-1918 ◽

Cited By ~ 13

Author(s):

Mohanan Geethalekshmi Sreeush ◽

Vinu Valsala ◽

Sreenivas Pentakota ◽

Koneru Venkata Siva Rama Prasad ◽

Raghu Murtugudde

Keyword(s):

Indian Ocean ◽

Solar Radiation ◽

Carbon Cycle ◽

Global Ocean ◽

New Production ◽

Monsoon Period ◽

Carbon Cycle Model ◽

Compensation Depth ◽

The Indian Ocean ◽

Ocean Carbon

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.

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Biological production in the Indian Ocean upwelling zones - Part 2: Data based estimates of variable compensation depth for ocean carbon models via cyclo-stationary Bayesian Inversion.

Deep Sea Research Part II Topical Studies in Oceanography ◽

10.1016/j.dsr2.2019.07.007 ◽

2020 ◽

Vol 179 ◽

pp. 104619 ◽

Cited By ~ 1

Author(s):

Mohanan Geethalekshmi Sreeush ◽

Vinu Valsala ◽

Halder Santanu ◽

Sreenivas Pentakota ◽

K.V.S.R. Prasad ◽

...

Keyword(s):

Indian Ocean ◽

Bayesian Inversion ◽

Biological Production ◽

Compensation Depth ◽

The Indian Ocean ◽

Ocean Carbon

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Simulation of the Natural Distribution of Carbon and Nutrients in the Ocean Based on the Global Ocean Carbon Cycle Model MOM4_L40

Chinese Journal of Geophysics ◽

10.1002/cjg2.20151 ◽

2015 ◽

Vol 58 (1) ◽

pp. 1-19 ◽

Cited By ~ 3

Author(s):

LI Qing-Quan ◽

TAN Juan ◽

WANG Lan-Ning ◽

WEI Min ◽

ZHAO Qi-Geng

Keyword(s):

Carbon Cycle ◽

Global Ocean ◽

Cycle Model ◽

Ocean Carbon Cycle ◽

Natural Distribution ◽

Carbon Cycle Model ◽

Ocean Carbon

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Strong sensitivity of Southern Ocean carbon uptake and nutrient cycling to wind stirring

Biogeosciences Discussions ◽

10.5194/bgd-10-15033-2013 ◽

2013 ◽

Vol 10 (9) ◽

pp. 15033-15076 ◽

Cited By ~ 1

Author(s):

K. B. Rodgers ◽

O. Aumont ◽

S. E. Mikaloff Fletcher ◽

Y. Plancherel ◽

L. Bopp ◽

...

Keyword(s):

Carbon Cycle ◽

Southern Ocean ◽

Ad Hoc ◽

Global Ocean ◽

Nutrient Concentrations ◽

Carbon Uptake ◽

Carbon Cycle Model ◽

Ocean Biogeochemistry ◽

Ocean Carbon ◽

The Impact

Abstract. Here we test the hypothesis that winds have an important role in determining the rate of exchange of CO2 between the atmosphere and ocean through wind stirring over the Southern Ocean. This is tested with a sensitivity study using an ad hoc parameterization of wind stirring in an ocean carbon cycle model. The objective is to identify the way in which perturbations to the vertical density structure of the planetary boundary in the ocean impacts the carbon cycle and ocean biogeochemistry. Wind stirring leads to reduced uptake of CO2 by the Southern Ocean over the period 2000–2006, with differences of order 0.9 Pg C yr−1 over the region south of 45° S. Wind stirring impacts not only the mean carbon uptake, but also the phasing of the seasonal cycle of carbon and other species associated with ocean biogeochemistry. Enhanced wind stirring delays the seasonal onset of stratification, and this has large impacts on both entrainment and the biological pump. It is also found that there is a strong sensitivity of nutrient concentrations exported in Subantarctic Mode Water (SAMW) to wind stirring. This finds expression not only locally over the Southern Ocean, but also over larger scales through the impact on advected nutrients. In summary, the large sensitivity identified with the ad hoc wind stirring parameterization offers support for the importance of wind stirring for global ocean biogeochemistry, through its impact over the Southern Ocean.

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An isopycnic ocean carbon cycle model

Geoscientific Model Development Discussions ◽

10.5194/gmdd-2-1023-2009 ◽

2009 ◽

Vol 2 (2) ◽

pp. 1023-1079 ◽

Cited By ~ 3

Author(s):

K. M. Assmann ◽

M. Bentsen ◽

J. Segschneider ◽

C. Heinze

Keyword(s):

Carbon Cycle ◽

Global Ocean ◽

System Modelling ◽

Surface Boundary ◽

Cycle Model ◽

Biological Production ◽

Carbon Cycle Model ◽

Export Production ◽

Sensitivity Studies ◽

Ocean Carbon

Abstract. The carbon cycle is a major forcing component in the global climate system. Modelling studies aiming to explain recent and past climatic changes and to project future ones thus increasingly include the interaction between the physical and biogeochemical systems. Their ocean components are generally z-coordinate models that are conceptually easy to use but that employ a vertical coordinate that is alien to the real ocean structure. Here we present first results from a newly developed isopycnic carbon cycle model and demonstrate the viability of using an isopycnic physical component for this purpose. As expected, the model represents interior ocean transport of biogeochemical tracers well and produces realistic tracer distributions. Difficulties in employing a purely isopycnic coordinate lie mainly in the treatment of the surface boundary layer which is often represented by a bulk mixed layer. The most significant adjustments of the biogeochemical code for use with an isopycnic coordinate are in the representation of upper ocean biological production. We present a series of sensitivity studies exploring the effect of changes in biogeochemical and physical processes on export production and nutrient distribution. Apart from giving us pointers for further model development, they highlight the importance of preformed nutrient distributions in the Southern Ocean for global nutrient distributions. Use of a prognostic slab atmosphere allows us to assess the effect of the changes in export production on global ocean carbon uptake and atmospheric CO2 levels. Sensitivity studies show that iron limitation for biological particle production, the treatment of light penetration for biological production, and the role of diapycnal mixing result in significant changes of modelled air-sea fluxes and nutrient distributions.

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Adjoint sensitivity of the air-sea CO<sub>2</sub> flux to ecosystem parameterization in a three-dimensional global ocean carbon cycle model

Biogeosciences Discussions ◽

10.5194/bgd-4-1377-2007 ◽

2007 ◽

Vol 4 (2) ◽

pp. 1377-1404 ◽

Cited By ~ 1

Author(s):

J. F. Tjiputra ◽

A. M. E. Winguth

Keyword(s):

Carbon Cycle ◽

Marine Ecosystem ◽

Three Dimensional ◽

Co2 Flux ◽

Global Ocean ◽

Ecosystem Structure ◽

Cycle Model ◽

Ocean Carbon Cycle ◽

Carbon Cycle Model ◽

Ocean Carbon

Abstract. The regional sensitivity of air-sea CO2 flux to ecosystem components and parameters in a three-dimensional ocean carbon cycle model is estimated using an adjoint model. Adjoint sensitivities to the global air-sea CO2 flux reveal that the biological component of the model is significant in the high latitudes of both hemispheres and in the Equatorial Pacific. More detailed analysis indicates that zooplankton grazing activity plays a major role in the carbon exchange in the above regions. The herbivores' ingestion parameter in the model regulates the flux of remineralized (i.e. regenerated) biogenic nutrients; thus, substantially controls the biological production and the concentration of dissolved inorganic carbon (DIC) in the euphotic zone. Over a 10-year period, reducing the herbivores' ingestion parameter in the model by 25% could increase the global uptake of atmospheric carbon by 6 Pg C. Thus, climate induced changes in the marine ecosystem structure are of importance for the future uptake of atmospheric CO2.

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Strong sensitivity of Southern Ocean carbon uptake and nutrient cycling to wind stirring

Biogeosciences ◽

10.5194/bg-11-4077-2014 ◽

2014 ◽

Vol 11 (15) ◽

pp. 4077-4098 ◽

Cited By ~ 29

Author(s):

K. B. Rodgers ◽

O. Aumont ◽

S. E. Mikaloff Fletcher ◽

Y. Plancherel ◽

L. Bopp ◽

...

Keyword(s):

Carbon Cycle ◽

Southern Ocean ◽

Ad Hoc ◽

Global Ocean ◽

Relative Reduction ◽

Carbon Uptake ◽

Carbon Cycle Model ◽

Ocean Biogeochemistry ◽

Ocean Carbon ◽

The Impact

Abstract. Here we test the hypothesis that winds have an important role in determining the rate of exchange of CO2 between the atmosphere and ocean through wind stirring over the Southern Ocean. This is tested with a sensitivity study using an ad hoc parameterization of wind stirring in an ocean carbon cycle model, where the objective is to identify the way in which perturbations to the vertical density structure of the planetary boundary in the ocean impacts the carbon cycle and ocean biogeochemistry. Wind stirring leads to reduced uptake of CO2 by the Southern Ocean over the period 2000–2006, with a relative reduction with wind stirring on the order of 0.9 Pg C yr−1 over the region south of 45° S. This impacts not only the mean carbon uptake, but also the phasing of the seasonal cycle of carbon and other ocean biogeochemical tracers. Enhanced wind stirring delays the seasonal onset of stratification, and this has large impacts on both entrainment and the biological pump. It is also found that there is a strong reduction on the order of 25–30% in the concentrations of NO3 exported in Subantarctic Mode Water (SAMW) to wind stirring. This finds expression not only locally over the Southern Ocean, but also over larger scales through the impact on advected nutrients. In summary, the large sensitivity identified with the ad hoc wind stirring parameterization offers support for the importance of wind stirring for global ocean biogeochemistry through its impact over the Southern Ocean.

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The IOD Impacts on the Indian Ocean Carbon Cycle

Journal of Geophysical Research Oceans ◽

10.1029/2020jc016485 ◽

2020 ◽

Vol 125 (11) ◽

Author(s):

Vinu Valsala ◽

M. G. Sreeush ◽

Kunal Chakraborty

Keyword(s):

Indian Ocean ◽

Carbon Cycle ◽

Ocean Carbon Cycle ◽

The Indian Ocean ◽

Ocean Carbon

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Beaching patterns of plastic debris along the Indian Ocean rim

10.5194/os-2020-50 ◽

2020 ◽

Author(s):

Mirjam van der Mheen ◽

Erik van Sebille ◽

Charitha Pattiaratchi

Keyword(s):

Indian Ocean ◽

Bay Of Bengal ◽

Plastic Material ◽

Monsoon Season ◽

Southwest Monsoon ◽

Plastic Waste ◽

Ocean Dynamics ◽

Global Ocean ◽

The Indian Ocean ◽

Southwest Monsoon Season

Abstract. A large percentage of global ocean plastic waste enters the northern hemisphere Indian Ocean (NIO). Despite this, it is unclear what happens to buoyant plastics in the NIO. Because the subtropics in the NIO is blocked by landmass, there is no subtropical gyre and no associated subtropical garbage patch in this region. We therefore hypothesise that plastics "beach" and end up on coastlines along the Indian Ocean rim. In this paper, we determine the influence of beaching plastics by applying different beaching conditions to Lagrangian particle tracking simulation results. Our results show that a large amount of plastic likely ends up on coastlines in the NIO, while some crosses the equator into the southern hemisphere Indian Ocean (SIO). In the NIO, the transport of plastics is dominated by seasonally reversing monsoonal currents, which transport plastics back and forth between the Arabian Sea and the Bay of Bengal. All buoyant plastic material in this region beaches within a few years in our simulations. Countries bordering the Bay of Bengal are particularly heavily affected by plastics beaching on coastlines. This is a result of both the large sources of plastic waste in the region, as well as ocean dynamics which concentrate plastics in the Bay of Bengal. During the intermonsoon period following the southwest monsoon season (September, October, November), plastics can cross the equator on the eastern side of the NIO basin into the SIO. Plastics that escape from the NIO into the SIO beach on eastern African coastlines and islands in the SIO or enter the subtropical SIO garbage patch.

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