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The seasonal cycle of CO₂ fluxes in the Southern Ocean: a model spatial scale sensitivity analysis
Includes bibliographical references
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| Main Author: | |
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| Other Authors: | |
| Format: | Thesis |
| Language: | English |
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Department of Oceanography
2018
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| _version_ | 1867614231865589760 |
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| access_status_str | Open Access |
| author | Mongwe, Ndunisani Precious |
| author2 | Monteiro, Pedro M S |
| author_browse | Mongwe, Ndunisani Precious Monteiro, Pedro M S |
| author_facet | Monteiro, Pedro M S Mongwe, Ndunisani Precious |
| author_sort | Mongwe, Ndunisani Precious |
| collection | Thesis |
| description | Includes bibliographical references |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/29014 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:48:45.884Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2018 |
| publishDateRange | 2018 |
| publishDateSort | 2018 |
| 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:11427/29014 The seasonal cycle of CO₂ fluxes in the Southern Ocean: a model spatial scale sensitivity analysis Mongwe, Ndunisani Precious Monteiro, Pedro M S Oceanography Ocean Systems and Climate Includes bibliographical references A recent study by Lenton et al., 2013, compared the mean seasonal cycle of air-sea CO₂ flux in the Southern Ocean(SO) over 1990 – 2009 period using five ocean biogeochemical models(BGMs) and atmospheric and ocean inversion models with monthly mean observations for the year 2000. This was done using a set of geographic boundaries to defined sub-domains of the SO consistent with the Regional Carbon Cycle and Assessment and Processes (RECCAP) protocol. Lenton et al., 2013 found that the seasonal cycle anomaly of the five BGMs better resolved observations of the air-sea CO₂ flux seasonal cycle in the SAZ, but was generally out phase with observations in the polar zone. In this study two setups of the ocean biogeochemical model NEMO PISCES was used to investigate the characteristics of the air-sea CO₂ flux seasonal cycle in the Southern Ocean in the period 1993- 2006. The study focused on two aspects i.e. (i) the sensitivity of air-sea CO₂ flux seasonal cycle to model resolution: comparing the ORCA2-LIM-PISCES (2° x 2° cos Ø) and PERIANT05 (NEMO-PISCES) (0.5° x 0.5° cos Ø) model configurations relative to climatological mean observations for the year 2000 (Takahashi et al., 2009) , and (ii) the sensitivity of air-sea CO₂ flux seasonal cycle to zonal boundary definition: comparing the air-sea CO₂ flux seasonal cycle and annual fluxes for three different boundaries i.e. Lenton 2013 RECCAP boundaries (44°S – 58°S and south of 58°S), geographic boundaries (40°S -50°S and south of 50°S) and dynamic boundaries (Sub-Antarctic Zone and Antarctic Zone, defined using climatological frontal positions). The seasonal cycle of the air-sea CO₂ flux in ORCA2 was found to be out of phase and overestimated the CO₂ flux compared to observations in almost all the sub-regions considered. The use of dynamic boundaries was found not to improve resolving observations seasonal cycle of air-sea CO₂ flux in both ORCA2 and PERIANT05. Boundary definition was found to affect the magnitude of ORCA2 annual air-sea CO₂ fluxes surface area based, where sub-regions of larger surface area gave larger annual CO₂ uptake and vice versa. This was mainly because ORCA2 air-sea CO₂ fluxes were found to show a general CO₂ in-gassing bias and spatially uniform in most parts of the SO and hence integration over a larger surface area gave larger annual fluxes. On the contrary PERIANT05 air-sea CO₂ fluxes spatial variability was not uniform in most parts of the SO however influenced by regional processes and hence annual fluxes were found not surface area based. The poor spatial representation and seasonal cycle sensitivity of ORCA2 air-sea CO₂ fluxes was found to be primarily due to lack or weak winter CO₂ entrainment and biological CO₂ draw down during the summer season. PERIANT05 on the contrary showed the effect of winter CO₂ entrainment, however maintains lack of or weak biological CO₂ draw down in the seasonal cycle. PERIANT05 was also found to show major weakness in the spatial representation of air-sea CO₂ fluxes north of the polar front with relative to T09 observations. 2018-11-06T14:04:12Z 2018-11-06T14:04:12Z 2014 Master Thesis Masters MSc http://hdl.handle.net/11427/29014 eng application/pdf Department of Oceanography Faculty of Science University of Cape Town |
| spellingShingle | Oceanography Ocean Systems and Climate Mongwe, Ndunisani Precious The seasonal cycle of CO₂ fluxes in the Southern Ocean: a model spatial scale sensitivity analysis |
| thesis_degree_str | Master's |
| title | The seasonal cycle of CO₂ fluxes in the Southern Ocean: a model spatial scale sensitivity analysis |
| title_full | The seasonal cycle of CO₂ fluxes in the Southern Ocean: a model spatial scale sensitivity analysis |
| title_fullStr | The seasonal cycle of CO₂ fluxes in the Southern Ocean: a model spatial scale sensitivity analysis |
| title_full_unstemmed | The seasonal cycle of CO₂ fluxes in the Southern Ocean: a model spatial scale sensitivity analysis |
| title_short | The seasonal cycle of CO₂ fluxes in the Southern Ocean: a model spatial scale sensitivity analysis |
| title_sort | seasonal cycle of co₂ fluxes in the southern ocean a model spatial scale sensitivity analysis |
| topic | Oceanography Ocean Systems and Climate |
| url | http://hdl.handle.net/11427/29014 |
| work_keys_str_mv | AT mongwendunisaniprecious theseasonalcycleofco2fluxesinthesouthernoceanamodelspatialscalesensitivityanalysis AT mongwendunisaniprecious seasonalcycleofco2fluxesinthesouthernoceanamodelspatialscalesensitivityanalysis |