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De l'interaction entre banquise, lumière et phytoplancton arctique

Marion Lebrun 1
1 NEMO R&D - Nucleus for European Modeling of the Ocean
LOCEAN - Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques
Abstract : Large weaknesses remain considering our understanding of the drivers of phytoplankton growth in Arctic sea ice zone, especially due to large uncertainties in the interactions between sea ice, light and phytoplankton.The aim of this PhD thesis is to better understand these interactions and to highlight the main uncertainties considering these interactions in Earth System Models. I first show that the ice-free period is mainly led by the solar irradiance cycle and by the ocean-atmosphere thermodynamic exchanges during summer. It is consequently projected to extend into fall in the future. Then, I evaluate the radiative transfer scheme in the ocean model NEMO, in arctic sea ice zone. I show that NEMO largely underestimates the transmitted shortwave radiation in ice-covered waters, especially due to the overestimation of the snow and the first level of the ocean attenuation. I finally define a diagnostic to describe available light seasonality in the sea ice zone and I study the impact of this diagnostic on simulated phytoplankton in the bio-geochemistry model PISCES. However, large uncertainties remain in the study of the relation between this diagnostic and the phytoplankton growth. This is especially due to the non-linearity between available light and phytoplankton growth and also due to the lake of knowledge about the phytoplankton physiology.
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Submitted on : Wednesday, November 25, 2020 - 9:47:08 AM
Last modification on : Thursday, January 14, 2021 - 3:17:21 AM


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  • HAL Id : tel-02918818, version 2


Marion Lebrun. De l'interaction entre banquise, lumière et phytoplancton arctique. Océanographie. Sorbonne Université, 2019. Français. ⟨NNT : 2019SORUS524⟩. ⟨tel-02918818v2⟩



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