Investigating future climate projections for southern Benguela using downscaled high-resolution climate models from the HighResMIP project (CMIP6)

Mbede, Sivuyisiwe

Investigating future climate projections for southern Benguela using downscaled high-resolution climate models from the HighResMIP project (CMIP6)

Thesis / Dissertation

2026

Publisher

University of Cape Town

Department

Department of Oceanography

Faculty

Faculty of Science

Abstract

The Southern Benguela Upwelling System (SBUS) is a climate-sensitive region characterised by significant environmental changes. This study investigates the relationship between the South Atlantic Anticyclone (SAA) and upwelling in the Southern Benguela, assessing how projected shifts in SAA due to climate changes may impact upwelling dynamics. The study used high-resolution models from the HighResMIP project within Coupled Model Intercomparison Project Phase 6 (CMIP6) to evaluate the responses of nearshore processes to large-scale changes caused by climate change. Future climate projections were analysed at a 25-km spatial resolution, allowing an assessment of nearshore responses to large-scale atmospheric changes. Future period simulations are based on the high-emissions scenario SSP5-8.5, similar to CMIP5 RCP8.5, and model simulations span historical (1950-2014) and future (2015-2050) periods. The results indicate a southward migration and intensification of the SAA, particularly during summer, strengthening local winds that will shift offshore and southward. These shifts will lead to the weakening of the alongshore upwelling intensity and a potential offshore displacement of climate-sensitive upwelling regions, characterised by intensified upwelling. These changes will impact nutrient availability, primary productivity, and the broader marine ecosystem, potentially impacting fisheries and coastal livelihoods. The Benguela Jet, crucial for transporting small pelagic fish eggs and larvae, is also projected to shift offshore weakening, reducing nearshore retention. While the study provides valuable insights, it acknowledges limitations in resolving finer-scale coastal processes at 25-km resolution and uncertainties inherent in high-emission projections. Future research should focus on refining regional downscaling techniques and further investigate the implications of these changes for adaptive, ecosystem-based management. Enhancing adaptive capacity through science-informed policy recommendations, community resilience strategies, and informed management practices will be essential to safeguard the region's ecological integrity and socio-economic sustainability as we approach 2050.