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Characterization of the Carbonate System across the Agulhas and Agulhas Return Currents
In this study, we investigate the role that the solubility and biological pumps have on CO₂ variability across the Agulhas Current system ( Agulhas Current and the Agulhas Return Current). The Agulhas Current system transports heat and salt from the Indian Ocean into the South Atlantic Ocean via the...
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| Format: | Thesis |
| Language: | English |
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Department of Oceanography
2015
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| _version_ | 1867613215578390528 |
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| access_status_str | Open Access |
| author | Melato, Lebohang Innocentia |
| author2 | Ansorge, Isabelle Jane |
| author_browse | Ansorge, Isabelle Jane Melato, Lebohang Innocentia |
| author_facet | Ansorge, Isabelle Jane Melato, Lebohang Innocentia |
| author_sort | Melato, Lebohang Innocentia |
| collection | Thesis |
| description | In this study, we investigate the role that the solubility and biological pumps have on CO₂ variability across the Agulhas Current system ( Agulhas Current and the Agulhas Return Current). The Agulhas Current system transports heat and salt from the Indian Ocean into the South Atlantic Ocean via the Agulhas leakage, which influences the Atlantic Meridional Overturning Circulation (AMOC). This study presents for the first time a characterization of the role the Agulhas Current system (Agulhas and Agulhas Return Currents) has on the uptake of anthropogenic CO₂. Fugacity of carbon dioxide (fCO₂ ) values were obtained from a ship-based underway pCO₂ (partial pressure of carbon dioxide) system and the air-sea CO₂ fluxes were computed using 6-hourly wind speeds from the NOAA Blended Sea Winds. An experiment was conducted during the Crossroads scientific monitoring line in May 2013, where surface dissolved inorganic carbon, total alkalinity and CO₂ flux were compared between the Agulhas and Agulhas Return Currents and the region directly south over the Agulhas Plateau. Our findings highlighted that the solubility and biological pumps played minimal to no role in the drawdown of carbon across the sub-Tropical zone and the Agulhas Current system (Agulhas and Agulhas Return Currents), due to opposing effect between chlorophyll and temperature on pCO₂ that explained why although there was carbon drawdown by primary production in the Agulhas and Agulhas Return Current regions, this does not play a role in enhancing the air-sea exchange of CO₂. The solubility pump was responsible for CO₂ in the sub-Antarctic zone. The biological and solubility pumps were responsible for CO₂ sink in the Agulhas Plateau eddy. The highest CO₂ flux in the study was observed in the Agulhas Plateau eddy at a flux value of -8.12 mmolC.m-².day-¹ due to the cooler mean sea surface temperature of ~16.5 °C. This is the first time that such as study has been undertaken and aims to provide a better understanding of the role of Western Boundary Currents such as the Agulhas Current has in the uptake of CO₂. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/15745 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:32:36.207Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2015 |
| publishDateRange | 2015 |
| publishDateSort | 2015 |
| publisher | Department of Oceanography |
| publisherStr | Department of Oceanography |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/15745 Characterization of the Carbonate System across the Agulhas and Agulhas Return Currents Melato, Lebohang Innocentia Ansorge, Isabelle Jane Monteiro, Pedro M S Ocean and Climate Dynamics In this study, we investigate the role that the solubility and biological pumps have on CO₂ variability across the Agulhas Current system ( Agulhas Current and the Agulhas Return Current). The Agulhas Current system transports heat and salt from the Indian Ocean into the South Atlantic Ocean via the Agulhas leakage, which influences the Atlantic Meridional Overturning Circulation (AMOC). This study presents for the first time a characterization of the role the Agulhas Current system (Agulhas and Agulhas Return Currents) has on the uptake of anthropogenic CO₂. Fugacity of carbon dioxide (fCO₂ ) values were obtained from a ship-based underway pCO₂ (partial pressure of carbon dioxide) system and the air-sea CO₂ fluxes were computed using 6-hourly wind speeds from the NOAA Blended Sea Winds. An experiment was conducted during the Crossroads scientific monitoring line in May 2013, where surface dissolved inorganic carbon, total alkalinity and CO₂ flux were compared between the Agulhas and Agulhas Return Currents and the region directly south over the Agulhas Plateau. Our findings highlighted that the solubility and biological pumps played minimal to no role in the drawdown of carbon across the sub-Tropical zone and the Agulhas Current system (Agulhas and Agulhas Return Currents), due to opposing effect between chlorophyll and temperature on pCO₂ that explained why although there was carbon drawdown by primary production in the Agulhas and Agulhas Return Current regions, this does not play a role in enhancing the air-sea exchange of CO₂. The solubility pump was responsible for CO₂ in the sub-Antarctic zone. The biological and solubility pumps were responsible for CO₂ sink in the Agulhas Plateau eddy. The highest CO₂ flux in the study was observed in the Agulhas Plateau eddy at a flux value of -8.12 mmolC.m-².day-¹ due to the cooler mean sea surface temperature of ~16.5 °C. This is the first time that such as study has been undertaken and aims to provide a better understanding of the role of Western Boundary Currents such as the Agulhas Current has in the uptake of CO₂. 2015-12-09T14:47:30Z 2015-12-09T14:47:30Z 2015 Master Thesis Masters MSc http://hdl.handle.net/11427/15745 eng application/pdf Department of Oceanography Faculty of Science University of Cape Town |
| spellingShingle | Ocean and Climate Dynamics Melato, Lebohang Innocentia Characterization of the Carbonate System across the Agulhas and Agulhas Return Currents |
| thesis_degree_str | Master's |
| title | Characterization of the Carbonate System across the Agulhas and Agulhas Return Currents |
| title_full | Characterization of the Carbonate System across the Agulhas and Agulhas Return Currents |
| title_fullStr | Characterization of the Carbonate System across the Agulhas and Agulhas Return Currents |
| title_full_unstemmed | Characterization of the Carbonate System across the Agulhas and Agulhas Return Currents |
| title_short | Characterization of the Carbonate System across the Agulhas and Agulhas Return Currents |
| title_sort | characterization of the carbonate system across the agulhas and agulhas return currents |
| topic | Ocean and Climate Dynamics |
| url | http://hdl.handle.net/11427/15745 |
| work_keys_str_mv | AT melatolebohanginnocentia characterizationofthecarbonatesystemacrosstheagulhasandagulhasreturncurrents |