Dynamique des blooms phytoplanctoniques dans le gyre subpolaire de l'Atlantique Nord

Abstract : The North Atlantic Subpolar Gyre exhibits the largest phytoplancton bloom of the global ocean. This major biological event plays a crucial role for the functioning of marine ecosystems and the global carbon cycle. The aim of this thesis is to better understand the bio-physical processes driving the dynamics of the phytoplankton bloom and carbon export at various spatiotemporal scales.In a first study, based on satellite data at a climatological scale, the subpolar gyre is bioregionalized according to distinct annual phytoplankton biomass cycles. The light-mixing regime controls the phytoplankton bloom dynamics in the different bioregions.In a second study, the new generation of BGC-Argo floats allowed for processes to be explored at a finer scale, especially during the overlooked winter season. In winter, intermittent and local restratifications of the mixed layer, triggered by sub-mesoscale processes, initiate transient winter blooms impacting the spring bloom dynamics.Finally, a third study showed how the high-frequency variability of the mixed layer depth during the winter-spring transition plays a crucial role on carbon export.
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Léo Lacour. Dynamique des blooms phytoplanctoniques dans le gyre subpolaire de l'Atlantique Nord. Oceanography. Université Pierre et Marie Curie - Paris VI, 2016. English. ⟨NNT : 2016PA066685⟩. ⟨tel-01595954⟩

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