Sub-mesoscale dynamics in The Southern Ocean
The Southern Ocean circulation is dominated by the Antarctic Circumpolar Current (ACC), a quasi-zonal current that encircles Antarctica. Typical features of the ACC are an energetic eddy field and jets that influence both the large scale flow and heat and carbon fluxes and, consequently, impact the...
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| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
| Published: |
2018
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| Online Access: | http://hdl.handle.net/1885/149833 https://doi.org/10.25911/5d5fc80446677 https://openresearch-repository.anu.edu.au/bitstream/1885/149833/5/b37620095_Rosso_I.pdf.jpg |
| Summary: | The Southern Ocean circulation is dominated by the Antarctic Circumpolar Current (ACC), a quasi-zonal current that encircles Antarctica. Typical features of the ACC are an energetic eddy field and jets that influence both the large scale flow and heat and carbon fluxes and, consequently, impact the climate system. Due to the strong zonal flow and weak stratification of the Southern Ocean, topography steers and influences the ACC. For example, Rossby waves or stationary meanders can be found in the lee of topographic features and the structure of jets and fronts can be modified by topography. ACC dynamics are very complex and understanding these dynamics is crucial, given the Southern Ocean role in the global climate system. The Southern Ocean is an environment where, despite a large nutrient availability, the biological productivity is very low. This biological activity is limited by light irradiance and iron availability. However, there exist several locations in the Southern Ocean where, due to a natural iron fertilisation, phytoplankton blooms can be observed. One such location is the Kerguelen Plateau (KP) region in the south Indian Ocean. Numerous physical mechanisms that drive iron into the euphotic zone of KP waters have been identified. However, in these studies sub-mesoscale dynamics, occurring at horizontal scales of several kilometers, have never been included and their contribution to the iron supply never estimated. These structures have been seen to dramatically trigger an ecosystem response in other parts of the ocean, suggesting that they might represent a significant contribution to Southern Ocean blooms. This thesis is focused on the development and analysis of the first sub-mesoscale-resolving (1/80 resolution) ocean model of the KP area. Resolving sub-mesoscale structures results in an enhancement of vertical velocities and transport, compared to mesoscale-resolving simulations (1/20). Results show that sub-mesoscale fields, such as eddy kinetic energy or vertical velocities, are spatially ... |
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