{"id":{"repo_id":"cape-town","oai_identifier":"oai:open.uct.ac.za:11427/35480"},"canonical_url":"https://search.dev.ndltd.org/etd/cape-town/oai:open.uct.ac.za:11427/35480","repository":{"repo_id":"cape-town","name":"University of Cape Town","base_url":"https://open.uct.ac.za/oai/request"},"display":{"title":"The influence of the land-sea breeze on coastal upwelling systems","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.","abstract_html":"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 (&lt;∼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&#x27;s). During relaxation events, mean SST&#x27;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.","abstract_has_math":false,"creators":["Fearon, Giles"],"institution":"Department of Oceanography","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Vichi, Marcello","Herbette, Steven","Veitch, Jennifer"],"committee_chairs":[],"committee_members":[],"year":2021,"date_issued":"2021","date_published":"2021","updated_at":"2026-07-24T01:34:19Z","subjects":["Oceanography"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/11427/35480","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Vichi, Marcello","Herbette, Steven","Veitch, Jennifer"]},{"key":"dc:creator","label":"Author","values":["Fearon, Giles"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2022-01-14T12:23:00Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2022-01-14T12:23:00Z"]},{"key":"dc:date.issued","label":"Date","values":["2021"]},{"key":"dc:publisher.department","label":"Dc Publisher Department","values":["Department of Oceanography"]},{"key":"dc:type","label":"Dc Type","values":["Doctoral Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["Doctoral","PhD"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Oceanography"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/11427/35480"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["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."]},{"key":"dc:title","label":"Title","values":["The influence of the land-sea breeze on coastal upwelling systems"]}]}],"canonical_facts":{"dc:contributor.advisor":["Vichi, Marcello","Herbette, Steven","Veitch, Jennifer"],"dc:creator":["Fearon, Giles"],"dc:date.accessioned":["2022-01-14T12:23:00Z"],"dc:date.available":["2022-01-14T12:23:00Z"],"dc:date.issued":["2021"],"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.uri":["http://hdl.handle.net/11427/35480"],"dc:publisher.department":["Department of Oceanography"],"dc:subject":["Oceanography"],"dc:title":["The influence of the land-sea breeze on coastal upwelling systems"],"dc:type":["Doctoral Thesis"],"dc:type.qualificationlevel":["Doctoral","PhD"]},"updated_at":"2026-07-24T01:34:19Z"}