Stirring, Mixing, Growing: Microscale Processes Change Larger Scale Phytoplankton Dynamics
The quantitative description of marine systems is constrained by a major issue of scale separation: phytoplankton production processes occur at sub-centimeter scales, while the contribution to the Earth's biogeochemical cycles is expressed at much larger scales, up to the planetary one. In spit...
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| Format: | Article |
| Language: | English |
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Frontiers Media S.A.
2020-08-01
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| Series: | Frontiers in Marine Science |
| Subjects: | |
| Online Access: | https://www.frontiersin.org/article/10.3389/fmars.2020.00654/full |
| _version_ | 1818192685687635968 |
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| author | Francesco Paparella Marcello Vichi |
| author_facet | Francesco Paparella Marcello Vichi |
| author_sort | Francesco Paparella |
| collection | DOAJ |
| description | The quantitative description of marine systems is constrained by a major issue of scale separation: phytoplankton production processes occur at sub-centimeter scales, while the contribution to the Earth's biogeochemical cycles is expressed at much larger scales, up to the planetary one. In spite of vastly improved computing power and observational capabilities, the modeling approach has remained anchored to an old view that sees the microscales as unable to substantially affect larger ones. The lack of a widespread theoretical appreciation of the interactions between vastly different scales has led to the proliferation of numerical models with uncertain predictive capabilities. In this paper, we use the phenology of phytoplankton blooms as one example of a macroscopic ecosystem feature affected by microscale interactions. We describe two distinct mechanisms that produce patchiness within a productive water column: turbulent entrainment of less-productive water at the base of the mixed layer, and stirring by slow turbulence of a vertical phytoplankton gradient sustained by depth-dependent light availability. In current eddy-diffusive models, patchiness produced in this way is wiped out very rapidly, because the time scales of irreversible mixing largely overlap those of mechanical stirring. We propose a novel Lagrangian modeling framework that allows for the existence of microscale patchiness, even when that is not fully resolved. We show, with a mixture of theoretical arguments and numerical simulations of increasing realism, how the presence of patchiness, in turn, affects larger-scale properties, demonstrating that the timing of phytoplankton blooms and vertical variability of chlorophyll in the oceanic upper layers is determined by the mutual interplay between the stirring, mixing and growing processes. |
| first_indexed | 2024-12-12T00:34:26Z |
| format | Article |
| id | doaj.art-a725dbcb3d354b768a87493e5a63adf1 |
| institution | Directory Open Access Journal |
| issn | 2296-7745 |
| language | English |
| last_indexed | 2024-12-12T00:34:26Z |
| publishDate | 2020-08-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Marine Science |
| spelling | doaj.art-a725dbcb3d354b768a87493e5a63adf12022-12-22T00:44:23ZengFrontiers Media S.A.Frontiers in Marine Science2296-77452020-08-01710.3389/fmars.2020.00654519394Stirring, Mixing, Growing: Microscale Processes Change Larger Scale Phytoplankton DynamicsFrancesco Paparella0Marcello Vichi1Division of Science and Center on Stability, Instability and Turbulence and Center for Astro, Particle, and Planetary Physics, New York University Abu Dhabi, Abu Dhabi, United Arab EmiratesDepartment of Oceanography and Marine Research Institute, University of Cape Town, Cape Town, South AfricaThe quantitative description of marine systems is constrained by a major issue of scale separation: phytoplankton production processes occur at sub-centimeter scales, while the contribution to the Earth's biogeochemical cycles is expressed at much larger scales, up to the planetary one. In spite of vastly improved computing power and observational capabilities, the modeling approach has remained anchored to an old view that sees the microscales as unable to substantially affect larger ones. The lack of a widespread theoretical appreciation of the interactions between vastly different scales has led to the proliferation of numerical models with uncertain predictive capabilities. In this paper, we use the phenology of phytoplankton blooms as one example of a macroscopic ecosystem feature affected by microscale interactions. We describe two distinct mechanisms that produce patchiness within a productive water column: turbulent entrainment of less-productive water at the base of the mixed layer, and stirring by slow turbulence of a vertical phytoplankton gradient sustained by depth-dependent light availability. In current eddy-diffusive models, patchiness produced in this way is wiped out very rapidly, because the time scales of irreversible mixing largely overlap those of mechanical stirring. We propose a novel Lagrangian modeling framework that allows for the existence of microscale patchiness, even when that is not fully resolved. We show, with a mixture of theoretical arguments and numerical simulations of increasing realism, how the presence of patchiness, in turn, affects larger-scale properties, demonstrating that the timing of phytoplankton blooms and vertical variability of chlorophyll in the oceanic upper layers is determined by the mutual interplay between the stirring, mixing and growing processes.https://www.frontiersin.org/article/10.3389/fmars.2020.00654/fullbiogeochemistryplankton modelinglagrangian particleBio-Geo-Chemical Argo (BGC-Argo)model bias and bias correctionphytoplankton bloom |
| spellingShingle | Francesco Paparella Marcello Vichi Stirring, Mixing, Growing: Microscale Processes Change Larger Scale Phytoplankton Dynamics Frontiers in Marine Science biogeochemistry plankton modeling lagrangian particle Bio-Geo-Chemical Argo (BGC-Argo) model bias and bias correction phytoplankton bloom |
| title | Stirring, Mixing, Growing: Microscale Processes Change Larger Scale Phytoplankton Dynamics |
| title_full | Stirring, Mixing, Growing: Microscale Processes Change Larger Scale Phytoplankton Dynamics |
| title_fullStr | Stirring, Mixing, Growing: Microscale Processes Change Larger Scale Phytoplankton Dynamics |
| title_full_unstemmed | Stirring, Mixing, Growing: Microscale Processes Change Larger Scale Phytoplankton Dynamics |
| title_short | Stirring, Mixing, Growing: Microscale Processes Change Larger Scale Phytoplankton Dynamics |
| title_sort | stirring mixing growing microscale processes change larger scale phytoplankton dynamics |
| topic | biogeochemistry plankton modeling lagrangian particle Bio-Geo-Chemical Argo (BGC-Argo) model bias and bias correction phytoplankton bloom |
| url | https://www.frontiersin.org/article/10.3389/fmars.2020.00654/full |
| work_keys_str_mv | AT francescopaparella stirringmixinggrowingmicroscaleprocesseschangelargerscalephytoplanktondynamics AT marcellovichi stirringmixinggrowingmicroscaleprocesseschangelargerscalephytoplanktondynamics |