K. Oglethorpe, B. Fernández Castro, C. P. Spingys, A. C. Naveira Garabato, R. G. Williams
{"title":"中尺度涡旋搅拌和微尺度湍流在维持副热带环流生物生产中的作用","authors":"K. Oglethorpe, B. Fernández Castro, C. P. Spingys, A. C. Naveira Garabato, R. G. Williams","doi":"10.1029/2024GB008180","DOIUrl":null,"url":null,"abstract":"<p>Sustaining phytoplankton primary production and organic carbon export requires the physical supply of nutrients to the sunlit ocean. In the extensive downwelling regions of the subtropical gyres, the pathways of this nutrient supply remain unclear. Vertical sinking of organic matter from the sunlit layer and its remineralization below cause net downward nutrient transfer in the upper subtropical ocean. Microscale mixing of nutrients across density surfaces and upwelling by mesoscale eddies and submesoscale fronts have been invoked to re-supply nutrients from the thermocline to the sunlit layer. However, a physical mechanism is required to replenish nutrients exported across the thermocline base and sustain a quasi-steady state upper-ocean nutrient budget on inter-annual timescales. Stirring along density surfaces by mesoscale eddies has emerged as a possible supply mechanism to close this nutrient budget. Here, we quantify the relative importance of mesoscale stirring and microscale mixing in supplying nutrients to the oligotrophic regions of the upper subtropical oceans, using global observationally based data sets for nutrients and diapycnal and isopycnal diffusivities. Mesoscale stirring dominates nutrient replenishment in the thermocline of subtropical gyres over microscale turbulence, contributing to 70%–90% of combined supply by the two processes. The stirring supply is most important along gyre flanks, where boundary currents and upwelling zones promote sharp nutrient gradients and vigorous mesoscale activity. Mesoscale fluxes provide sufficient nutrients to offset depletion in the thermocline due to upward microscale mixing into the sunlit layer. This analysis suggests that eddy stirring is significant in maintaining organic carbon export within subtropical gyres.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 9","pages":""},"PeriodicalIF":5.5000,"publicationDate":"2025-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008180","citationCount":"0","resultStr":"{\"title\":\"The Role of Mesoscale Eddy Stirring and Microscale Turbulence in Sustaining Biological Production in the Subtropical Gyres\",\"authors\":\"K. Oglethorpe, B. Fernández Castro, C. P. Spingys, A. C. Naveira Garabato, R. G. Williams\",\"doi\":\"10.1029/2024GB008180\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p>Sustaining phytoplankton primary production and organic carbon export requires the physical supply of nutrients to the sunlit ocean. In the extensive downwelling regions of the subtropical gyres, the pathways of this nutrient supply remain unclear. Vertical sinking of organic matter from the sunlit layer and its remineralization below cause net downward nutrient transfer in the upper subtropical ocean. Microscale mixing of nutrients across density surfaces and upwelling by mesoscale eddies and submesoscale fronts have been invoked to re-supply nutrients from the thermocline to the sunlit layer. However, a physical mechanism is required to replenish nutrients exported across the thermocline base and sustain a quasi-steady state upper-ocean nutrient budget on inter-annual timescales. Stirring along density surfaces by mesoscale eddies has emerged as a possible supply mechanism to close this nutrient budget. Here, we quantify the relative importance of mesoscale stirring and microscale mixing in supplying nutrients to the oligotrophic regions of the upper subtropical oceans, using global observationally based data sets for nutrients and diapycnal and isopycnal diffusivities. Mesoscale stirring dominates nutrient replenishment in the thermocline of subtropical gyres over microscale turbulence, contributing to 70%–90% of combined supply by the two processes. The stirring supply is most important along gyre flanks, where boundary currents and upwelling zones promote sharp nutrient gradients and vigorous mesoscale activity. Mesoscale fluxes provide sufficient nutrients to offset depletion in the thermocline due to upward microscale mixing into the sunlit layer. 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The Role of Mesoscale Eddy Stirring and Microscale Turbulence in Sustaining Biological Production in the Subtropical Gyres
Sustaining phytoplankton primary production and organic carbon export requires the physical supply of nutrients to the sunlit ocean. In the extensive downwelling regions of the subtropical gyres, the pathways of this nutrient supply remain unclear. Vertical sinking of organic matter from the sunlit layer and its remineralization below cause net downward nutrient transfer in the upper subtropical ocean. Microscale mixing of nutrients across density surfaces and upwelling by mesoscale eddies and submesoscale fronts have been invoked to re-supply nutrients from the thermocline to the sunlit layer. However, a physical mechanism is required to replenish nutrients exported across the thermocline base and sustain a quasi-steady state upper-ocean nutrient budget on inter-annual timescales. Stirring along density surfaces by mesoscale eddies has emerged as a possible supply mechanism to close this nutrient budget. Here, we quantify the relative importance of mesoscale stirring and microscale mixing in supplying nutrients to the oligotrophic regions of the upper subtropical oceans, using global observationally based data sets for nutrients and diapycnal and isopycnal diffusivities. Mesoscale stirring dominates nutrient replenishment in the thermocline of subtropical gyres over microscale turbulence, contributing to 70%–90% of combined supply by the two processes. The stirring supply is most important along gyre flanks, where boundary currents and upwelling zones promote sharp nutrient gradients and vigorous mesoscale activity. Mesoscale fluxes provide sufficient nutrients to offset depletion in the thermocline due to upward microscale mixing into the sunlit layer. This analysis suggests that eddy stirring is significant in maintaining organic carbon export within subtropical gyres.
期刊介绍:
Global Biogeochemical Cycles (GBC) features research on regional to global biogeochemical interactions, as well as more local studies that demonstrate fundamental implications for biogeochemical processing at regional or global scales. Published papers draw on a wide array of methods and knowledge and extend in time from the deep geologic past to recent historical and potential future interactions. This broad scope includes studies that elucidate human activities as interactive components of biogeochemical cycles and physical Earth Systems including climate. Authors are required to make their work accessible to a broad interdisciplinary range of scientists.