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- Title
Oceanic Fronts Structure Phytoplankton Distributions in the Central South Indian Ocean.
- Authors
Guo, Mingxian; Xiu, Peng; Xing, Xiaogang
- Abstract
In the South Indian Ocean (SIO), high surface chlorophyll concentrations are often observed in mesoscale anticyclonic eddy cores. Yet the role of submesoscale dynamics in modulating phytoplankton distributions remains largely unknown in the region. By using a biogeochemical‐Argo float and a high‐resolution model, we show that elevated chlorophyll concentrations were evident in a frontal region, and the depth‐integrated chlorophyll in this frontal region can be higher than that in the anticyclonic eddy core. Submesoscale frontogenesis was shown to inject nutrients vertically and enhance phytoplankton growth in the frontal region. Frontal dynamics tend to facilitate large phytoplankton such as diatom growth, which consequently increases diatom fraction. Over the entire central SIO, we found a significant correlation between the phytoplankton composition index and frontogenesis. However, the correlation between total phytoplankton biomass and frontogenesis was not significant. These results demonstrate the complex role of frontal dynamics in structuring phytoplankton distributions in the central SIO. Plain Language Summary: Mesoscale eddies and submesoscale processes are widely distributed in global oceans and are often dynamically connected. In the central South Indian Ocean (SIO), mesoscale anticyclonic eddies have been suggested to contribute greatly to the observed high concentration of surface phytoplankton chlorophyll. Yet the influence of submesoscale processes on phytoplankton distribution has not been fully studied. We used a biogeochemical‐Argo profiling float and a high‐resolution ocean model to evaluate this influence. We show that the chlorophyll in the submesoscale frontal region can be higher than that in the anticyclonic eddy core. A frontal region is associated with vertical nutrient supply, which favors phytoplankton growth, especially for large phytoplankton. Thus, for the entire central SIO, submesoscale processes play an important role in structuring phytoplankton distributions Key Points: Localized chlorophyll enhancement and submesoscale structures in a frontal region were captured by a biogeochemical‐Argo float in the central SIOHigh‐resolution simulations revealed that frontogenesis leads to nutrient injections and induces high chlorophyll in the frontal regionAt the basin scale, a significant correlation between frontogenesis and the phytoplankton composition index was found in the central SIO
- Subjects
INDIAN Ocean; PHYTOPLANKTON; CHLOROPHYLL; MESOSCALE eddies; STATISTICAL correlation
- Publication
Journal of Geophysical Research. Oceans, 2022, Vol 127, Issue 1, p1
- ISSN
2169-9275
- Publication type
Article
- DOI
10.1029/2021JC017594