Marine heatwaves and warm events in the Cape Peninsula upwelling cell, Southern Benguela

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dc.contributor.advisorLamont, Tarron
dc.contributor.advisorRouault, Mathieu
dc.contributor.authorPetzer, Kirstin Robyn
dc.date.accessioned2026-04-24T06:36:27Z
dc.date.available2026-04-24T06:36:27Z
dc.date.issued2023
dc.date.updated2026-04-23T13:44:09Z
dc.description.abstractDue to global warming, Marine Heatwaves (MHWs) are considered to be one of the emerging threats to marine ecosystems globally. MHWs are prolonged periods of extreme warm Sea Surface Temperature (SST) anomalies which can cause severe ecological impacts by decreasing biodiversity, negatively affecting cold water species and increasing ocean stratification. Using the Cape Point CSIR half-hourly in situ SST, CCI, REMSS, ERA5 wind time series, over 17-years the occurrence from January 2003 to March 2020, duration and maximum SST values as well as the influence of the wind on the formation and end on marine heatwaves and warm events (WEs) at a single location in the Cape Peninsula Cell, in the Southern Benguela, was examined. The MHW events were identified using Hobday et al. (2016), when the SST exceeds the climatological 90th percentile for at least five days. The WE events, defined similarly to a MHW but the SST must exceed the climatological 90th percentile for at least three days, are also studied due to the high variability of the Southern Benguela. In the half-hourly CSIR time series 14 MHWs and 21 WEs occurred over the 17 years. The average duration is between 7 to 8 days but the longest events occurred during periods of decreased upwelling but the highest maximum SSTs occur during the periods of upwelling dominance. The daily CSIR, CCI and REMSS time series all identified double the number of MHWs and WEs events than the half-hourly time series, raising the concern of applying the Hobday et al. (2016) definition to sub-daily time series and the ability of satellites to be used for MHW identification in the Southern Benguela close to the coast. The dominant wind at the formation of MHWs and WEs is a north-westerly wind, indicating the main driver of events at the CSIR Cape Point mooring is the movement of warm water masses to the mooring location. The dominant wind direction at the end of the MHWs and WEs is a south-easterly wind indicating that coastal upwelling limits the duration of warm water events at the Cape Point mooring. Marine heatwaves are expected to worsen globally with climate change by lasting longer with high temperature increases but the projected increase in southeasterly winds could further limit the duration of MHWs in the Southern Benguela upwelling system.
dc.identifier.apacitationPetzer, K. R. (2023). <i>Marine heatwaves and warm events in the Cape Peninsula upwelling cell, Southern Benguela</i>. (). University of Cape Town ,Faculty of Science ,Department of Oceanography. Retrieved from http://hdl.handle.net/11427/43133en_ZA
dc.identifier.chicagocitationPetzer, Kirstin Robyn. <i>"Marine heatwaves and warm events in the Cape Peninsula upwelling cell, Southern Benguela."</i> ., University of Cape Town ,Faculty of Science ,Department of Oceanography, 2023. http://hdl.handle.net/11427/43133en_ZA
dc.identifier.citationPetzer, K.R. 2023. Marine heatwaves and warm events in the Cape Peninsula upwelling cell, Southern Benguela. . University of Cape Town ,Faculty of Science ,Department of Oceanography. http://hdl.handle.net/11427/43133en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Petzer, Kirstin Robyn AB - Due to global warming, Marine Heatwaves (MHWs) are considered to be one of the emerging threats to marine ecosystems globally. MHWs are prolonged periods of extreme warm Sea Surface Temperature (SST) anomalies which can cause severe ecological impacts by decreasing biodiversity, negatively affecting cold water species and increasing ocean stratification. Using the Cape Point CSIR half-hourly in situ SST, CCI, REMSS, ERA5 wind time series, over 17-years the occurrence from January 2003 to March 2020, duration and maximum SST values as well as the influence of the wind on the formation and end on marine heatwaves and warm events (WEs) at a single location in the Cape Peninsula Cell, in the Southern Benguela, was examined. The MHW events were identified using Hobday et al. (2016), when the SST exceeds the climatological 90th percentile for at least five days. The WE events, defined similarly to a MHW but the SST must exceed the climatological 90th percentile for at least three days, are also studied due to the high variability of the Southern Benguela. In the half-hourly CSIR time series 14 MHWs and 21 WEs occurred over the 17 years. The average duration is between 7 to 8 days but the longest events occurred during periods of decreased upwelling but the highest maximum SSTs occur during the periods of upwelling dominance. The daily CSIR, CCI and REMSS time series all identified double the number of MHWs and WEs events than the half-hourly time series, raising the concern of applying the Hobday et al. (2016) definition to sub-daily time series and the ability of satellites to be used for MHW identification in the Southern Benguela close to the coast. The dominant wind at the formation of MHWs and WEs is a north-westerly wind, indicating the main driver of events at the CSIR Cape Point mooring is the movement of warm water masses to the mooring location. The dominant wind direction at the end of the MHWs and WEs is a south-easterly wind indicating that coastal upwelling limits the duration of warm water events at the Cape Point mooring. Marine heatwaves are expected to worsen globally with climate change by lasting longer with high temperature increases but the projected increase in southeasterly winds could further limit the duration of MHWs in the Southern Benguela upwelling system. DA - 2023 DB - OpenUCT DP - University of Cape Town KW - Oceanography KW - Cape Point CSIR KW - Marine Heatwaves KW - Southern Benguela KW - Cape Peninsula Cell LK - https://open.uct.ac.za PB - University of Cape Town PY - 2023 T1 - Marine heatwaves and warm events in the Cape Peninsula upwelling cell, Southern Benguela TI - Marine heatwaves and warm events in the Cape Peninsula upwelling cell, Southern Benguela UR - http://hdl.handle.net/11427/43133 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/43133
dc.identifier.vancouvercitationPetzer KR. Marine heatwaves and warm events in the Cape Peninsula upwelling cell, Southern Benguela. []. University of Cape Town ,Faculty of Science ,Department of Oceanography, 2023 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/43133en_ZA
dc.language.isoen
dc.language.rfc3066eng
dc.publisher.departmentDepartment of Oceanography
dc.publisher.facultyFaculty of Science
dc.publisher.institutionUniversity of Cape Town
dc.subjectOceanography
dc.subjectCape Point CSIR
dc.subjectMarine Heatwaves
dc.subjectSouthern Benguela
dc.subjectCape Peninsula Cell
dc.titleMarine heatwaves and warm events in the Cape Peninsula upwelling cell, Southern Benguela
dc.typeThesis / Dissertation
dc.type.qualificationlevelMasters
dc.type.qualificationlevelMasters
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