From alpha to beta ocean: Exploring the role of surface buoyancy fluxes and seawater thermal expansion in setting the upper ocean stratification
The ocean plays a central role in the climate system by absorbing excess anthropogenic heat and carbon dioxide. Moreover, the ocean circulation distributes heat from the tropics towards the poles. Due to the large ocean stratification, vertical exchanges between the ocean interior and the surface ar...
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ftunivgoeteborg:oai:gupea.ub.gu.se:2077/79117 2023-12-31T10:00:04+01:00 From alpha to beta ocean: Exploring the role of surface buoyancy fluxes and seawater thermal expansion in setting the upper ocean stratification Caneill, Romain 2023-12-05 application/pdf https://hdl.handle.net/2077/79117 eng eng Caneill, R., Roquet, F., Madec, G., & Nycander, J. (2022). The Polar Transition from Alpha to Beta Regions Set by a Surface Buoyancy Flux Inversion. Journal of Physical Oceanography, 52 (8), 1887–1902. https://doi.org/10.1175/JPO-D-21-0295.1 Caneill, R., Roquet, F., & Nycander, J. (2023). Southern Ocean deep mixing band emerges from competition between winter buoyancy loss and stratification. submitted to Ocean Science. https://doi.org/10.5194/egusphere-2023-2404 Caneill, R., & Roquet, F. (2023). Temperature versus salinity: Distribution of stratification control in the global ocean. in preparation for Ocean Science Roquet, F., Ferreira, D., Caneill, R., Schlesinger, D., & Madec, G. (2022). Unique thermal expansion properties of water key to the formation of sea ice on Earth. Science Advances, 8 (46). https://doi.org/10.1126/sciadv.abq0793 978-91-8069-556-5 (pdf) 978-91-8069-555-8 (printed) https://hdl.handle.net/2077/79117 Ocean stratification Thermal expansion coefficient Buoyancy fluxes Transition zone Alpha – beta ocean text Doctoral thesis Doctor of Philosophy 2023 ftunivgoeteborg 2023-12-06T23:30:23Z The ocean plays a central role in the climate system by absorbing excess anthropogenic heat and carbon dioxide. Moreover, the ocean circulation distributes heat from the tropics towards the poles. Due to the large ocean stratification, vertical exchanges between the ocean interior and the surface are limited. Subduction links the ocean surface and its interior and occurs in winter at mid- or high-latitudes, where the mixed layers (MLs) are deep. In subtropical regions, temperature and salinity decrease below the ML. Temperature has thus a stabilising effect, while salinity has a destabilising effect, a stratification regime called alpha ocean. Opposite, in polar regions, temperature and salinity increase below the ML, and salinity is the stabilising factor, a regime called beta ocean. In between these two regimes lies the polar transition zone (PTZ), where both temperature and salinity are stabilising. Despite the importance of the alpha-beta distinction, the underlying mechanisms controlling these regimes remain unclear. This thesis investigates the factors influencing the upper ocean stratification and the deep MLs adjacent to the PTZs. From observational profiles, we produce novel climatologies of the upper ocean properties. These climatologies confirm that MLs are deep on the poleward flanks of the alpha oceans. Deep MLs are also present in the beta ocean along the coast of Antarctica. In winter, the transition between the different regimes is abrupt. In summer, both temperature and salinity stratify almost the entire ocean. Based on idealised numerical simulations and observations, we find that the buoyancy fluxes largely determine the position of the PTZ. By stabilising the water column poleward of the PTZ, buoyancy fluxes inhibit convection, permitting beta-ocean formation. The exact position of the PTZ and the adjacent deep MLs are determined by the competition between the winter buoyancy loss and the strength of the existing stratification. Importantly, the impact of heat flux on buoyancy is scaled by ... Doctoral or Postdoctoral Thesis Antarc* Antarctica University of Gothenburg: GUPEA (Gothenburg University Publications Electronic Archive) |
institution |
Open Polar |
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University of Gothenburg: GUPEA (Gothenburg University Publications Electronic Archive) |
op_collection_id |
ftunivgoeteborg |
language |
English |
topic |
Ocean stratification Thermal expansion coefficient Buoyancy fluxes Transition zone Alpha – beta ocean |
spellingShingle |
Ocean stratification Thermal expansion coefficient Buoyancy fluxes Transition zone Alpha – beta ocean Caneill, Romain From alpha to beta ocean: Exploring the role of surface buoyancy fluxes and seawater thermal expansion in setting the upper ocean stratification |
topic_facet |
Ocean stratification Thermal expansion coefficient Buoyancy fluxes Transition zone Alpha – beta ocean |
description |
The ocean plays a central role in the climate system by absorbing excess anthropogenic heat and carbon dioxide. Moreover, the ocean circulation distributes heat from the tropics towards the poles. Due to the large ocean stratification, vertical exchanges between the ocean interior and the surface are limited. Subduction links the ocean surface and its interior and occurs in winter at mid- or high-latitudes, where the mixed layers (MLs) are deep. In subtropical regions, temperature and salinity decrease below the ML. Temperature has thus a stabilising effect, while salinity has a destabilising effect, a stratification regime called alpha ocean. Opposite, in polar regions, temperature and salinity increase below the ML, and salinity is the stabilising factor, a regime called beta ocean. In between these two regimes lies the polar transition zone (PTZ), where both temperature and salinity are stabilising. Despite the importance of the alpha-beta distinction, the underlying mechanisms controlling these regimes remain unclear. This thesis investigates the factors influencing the upper ocean stratification and the deep MLs adjacent to the PTZs. From observational profiles, we produce novel climatologies of the upper ocean properties. These climatologies confirm that MLs are deep on the poleward flanks of the alpha oceans. Deep MLs are also present in the beta ocean along the coast of Antarctica. In winter, the transition between the different regimes is abrupt. In summer, both temperature and salinity stratify almost the entire ocean. Based on idealised numerical simulations and observations, we find that the buoyancy fluxes largely determine the position of the PTZ. By stabilising the water column poleward of the PTZ, buoyancy fluxes inhibit convection, permitting beta-ocean formation. The exact position of the PTZ and the adjacent deep MLs are determined by the competition between the winter buoyancy loss and the strength of the existing stratification. Importantly, the impact of heat flux on buoyancy is scaled by ... |
format |
Doctoral or Postdoctoral Thesis |
author |
Caneill, Romain |
author_facet |
Caneill, Romain |
author_sort |
Caneill, Romain |
title |
From alpha to beta ocean: Exploring the role of surface buoyancy fluxes and seawater thermal expansion in setting the upper ocean stratification |
title_short |
From alpha to beta ocean: Exploring the role of surface buoyancy fluxes and seawater thermal expansion in setting the upper ocean stratification |
title_full |
From alpha to beta ocean: Exploring the role of surface buoyancy fluxes and seawater thermal expansion in setting the upper ocean stratification |
title_fullStr |
From alpha to beta ocean: Exploring the role of surface buoyancy fluxes and seawater thermal expansion in setting the upper ocean stratification |
title_full_unstemmed |
From alpha to beta ocean: Exploring the role of surface buoyancy fluxes and seawater thermal expansion in setting the upper ocean stratification |
title_sort |
from alpha to beta ocean: exploring the role of surface buoyancy fluxes and seawater thermal expansion in setting the upper ocean stratification |
publishDate |
2023 |
url |
https://hdl.handle.net/2077/79117 |
genre |
Antarc* Antarctica |
genre_facet |
Antarc* Antarctica |
op_relation |
Caneill, R., Roquet, F., Madec, G., & Nycander, J. (2022). The Polar Transition from Alpha to Beta Regions Set by a Surface Buoyancy Flux Inversion. Journal of Physical Oceanography, 52 (8), 1887–1902. https://doi.org/10.1175/JPO-D-21-0295.1 Caneill, R., Roquet, F., & Nycander, J. (2023). Southern Ocean deep mixing band emerges from competition between winter buoyancy loss and stratification. submitted to Ocean Science. https://doi.org/10.5194/egusphere-2023-2404 Caneill, R., & Roquet, F. (2023). Temperature versus salinity: Distribution of stratification control in the global ocean. in preparation for Ocean Science Roquet, F., Ferreira, D., Caneill, R., Schlesinger, D., & Madec, G. (2022). Unique thermal expansion properties of water key to the formation of sea ice on Earth. Science Advances, 8 (46). https://doi.org/10.1126/sciadv.abq0793 978-91-8069-556-5 (pdf) 978-91-8069-555-8 (printed) https://hdl.handle.net/2077/79117 |
_version_ |
1786845550632501248 |