The influence of the land-sea breeze on coastal upwelling systems
| dc.contributor.advisor | Vichi, Marcello | |
| dc.contributor.advisor | Herbette, Steven | |
| dc.contributor.advisor | Veitch, Jennifer | |
| dc.contributor.author | Fearon, Giles | |
| dc.date.accessioned | 2022-01-14T12:23:00Z | |
| dc.date.available | 2022-01-14T12:23:00Z | |
| dc.date.issued | 2021 | |
| dc.date.updated | 2022-01-13T09:08:52Z | |
| dc.description.abstract | The land-sea breeze is resonant with the inertial response of the ocean at the critical latitude of 30° N/S, however its role in the physical and biogeochemical functioning of eastern boundary upwelling systems (EBUS) is often over-looked. Here, we present a series of 1D, 2D, and 3D numerical experiments which elucidate the drivers of diurnal-inertial variability and vertical mixing in EBUS due to land-sea breeze forcing near the critical latitude. The amplitude of the diurnal anticyclonic rotary component of the wind stress (τ ac0 ) is shown to be a good predictor of the locally forced response. The water depth plays an important role, where for shallow water depths (<∼100 m) surface oscillations are dampened and shear-driven mixing at the thermocline is reduced. Convergence/ divergence of the forced surface oscillations drive evanescent internal waves which elevate local vertical mixing above that from the forced response alone. The internal wave response is dampened by a gradually sloping bottom topography. St Helena Bay (∼32.5° S), in the southern Benguela upwelling system, possesses a combination of physical characteristics which favour an enhanced response to the land-sea breeze, namely a near-critical latitude, a local enhancement of τ ac0 , and a tendency for the development of a shallow stratified surface layer. Here, land-sea breeze forcing contributes to large diurnal variability in sea surface temperatures (SST's). During relaxation events, mean SST's are notably reduced due to land-sea breeze-driven vertical mixing. During upwelling events, the land-sea breeze drives a net warming of inner shelf waters primarily due to enhanced retention of the deepened surface mixed layer. The deepened thermocline impacts geostrophically-driven alongshore currents within St Helena Bay, which are strengthened (weakened) during upwelling (relaxation) events. It appears likely that the land-sea breeze plays an important role in the productivity of the system. | |
| dc.identifier.apacitation | Fearon, G. (2021). <i>The influence of the land-sea breeze on coastal upwelling systems</i>. (). ,Faculty of Science ,Department of Oceanography. Retrieved from http://hdl.handle.net/11427/35480 | en_ZA |
| dc.identifier.chicagocitation | Fearon, Giles. <i>"The influence of the land-sea breeze on coastal upwelling systems."</i> ., ,Faculty of Science ,Department of Oceanography, 2021. http://hdl.handle.net/11427/35480 | en_ZA |
| dc.identifier.citation | Fearon, G. 2021. The influence of the land-sea breeze on coastal upwelling systems. . ,Faculty of Science ,Department of Oceanography. http://hdl.handle.net/11427/35480 | en_ZA |
| dc.identifier.ris | TY - Doctoral Thesis AU - Fearon, Giles AB - The land-sea breeze is resonant with the inertial response of the ocean at the critical latitude of 30° N/S, however its role in the physical and biogeochemical functioning of eastern boundary upwelling systems (EBUS) is often over-looked. Here, we present a series of 1D, 2D, and 3D numerical experiments which elucidate the drivers of diurnal-inertial variability and vertical mixing in EBUS due to land-sea breeze forcing near the critical latitude. The amplitude of the diurnal anticyclonic rotary component of the wind stress (τ ac0 ) is shown to be a good predictor of the locally forced response. The water depth plays an important role, where for shallow water depths (<∼100 m) surface oscillations are dampened and shear-driven mixing at the thermocline is reduced. Convergence/ divergence of the forced surface oscillations drive evanescent internal waves which elevate local vertical mixing above that from the forced response alone. The internal wave response is dampened by a gradually sloping bottom topography. St Helena Bay (∼32.5° S), in the southern Benguela upwelling system, possesses a combination of physical characteristics which favour an enhanced response to the land-sea breeze, namely a near-critical latitude, a local enhancement of τ ac0 , and a tendency for the development of a shallow stratified surface layer. Here, land-sea breeze forcing contributes to large diurnal variability in sea surface temperatures (SST's). During relaxation events, mean SST's are notably reduced due to land-sea breeze-driven vertical mixing. During upwelling events, the land-sea breeze drives a net warming of inner shelf waters primarily due to enhanced retention of the deepened surface mixed layer. The deepened thermocline impacts geostrophically-driven alongshore currents within St Helena Bay, which are strengthened (weakened) during upwelling (relaxation) events. It appears likely that the land-sea breeze plays an important role in the productivity of the system. DA - 2021_ DB - OpenUCT DP - University of Cape Town KW - Oceanography LK - https://open.uct.ac.za PY - 2021 T1 - The influence of the land-sea breeze on coastal upwelling systems TI - The influence of the land-sea breeze on coastal upwelling systems UR - http://hdl.handle.net/11427/35480 ER - | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/11427/35480 | |
| dc.identifier.vancouvercitation | Fearon G. The influence of the land-sea breeze on coastal upwelling systems. []. ,Faculty of Science ,Department of Oceanography, 2021 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/35480 | en_ZA |
| dc.language.rfc3066 | eng | |
| dc.publisher.department | Department of Oceanography | |
| dc.publisher.faculty | Faculty of Science | |
| dc.subject | Oceanography | |
| dc.title | The influence of the land-sea breeze on coastal upwelling systems | |
| dc.type | Doctoral Thesis | |
| dc.type.qualificationlevel | Doctoral | |
| dc.type.qualificationlevel | PhD |