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2013 students

Project title: Investigating the effect of variability in the position of the Subantarctic Front on the
environmental conditions of the Prince Edward Islands

Lying directly within the Antarctic Circumpolar Current (ACC), the sub-Antarctic islands, such as Prince  Edward islands (PEIs), provide an ideal ecological laboratory for studying how shifts in atmospheric and oceanic circulation patterns in the indian sector of the Southern Ocean affect their ecosystems. In the perspective of understanding better the impact of climate change on ecosystems of PEIs, one fundamental step is to clarify whether and how migrations of the Sub-Antarctic Front (SAF) exert an influence on hydrodynamic and environmental conditions near the islands. ORCA12 simulations at 1/12 resolution and BIOPERIANT05 dynamic-biogeochemical coupled simulations at 1/2 resolution are used to investigate on the link between the large scale migration of the Sub-Antarctic Front and the conditions around PEIs. Our results are different depending on the configuration. In BIOPERIANT05, the SAF shows low-frequency southward shift wich is not represented in ORCA12, where it is most concealed by interranual variations.
Besides, the simulations highlight that the representation of the islands in the model is important because they generate mesoscale processes that affect the heat content fluctuations in the vicinity of the islands. The direct link between SAF migration and heat content, as suggested in observations, is only visible in simulations at interannual frequencies. Concerning the biology in BIOPERIANT05, we observe no direct relation between biological variables and SAF position, whatever the frequency.

This study indicates that a high resolution ocean model coupled to a biogeochemistry model in long-term simulations is essential for the understanding of the link between large scale Southern Ocean fluctuations and hydrodynamic and environmental conditions around PEIs.

 

 Link to the whole report document : click here

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