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Dissolved and particulate iron in the Atlantic sector marginal ice zone of the Southern Ocean
Thesis (MSc)--Stellenbosch University, 2025.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867614011292385280 |
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| access_status_str | Open Access |
| author | Buchanan, Kayla |
| author2 | Roychoudhury, A. N. |
| author_browse | Buchanan, Kayla Roychoudhury, A. N. |
| author_facet | Roychoudhury, A. N. Buchanan, Kayla |
| author_sort | Buchanan, Kayla |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2025. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/134546 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:45:15.253Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/134546 Dissolved and particulate iron in the Atlantic sector marginal ice zone of the Southern Ocean Buchanan, Kayla Roychoudhury, A. N. Samanta, S. Stellenbosch University. Faculty of Science. Dept. of Earth Sciences. Iron -- Environmental aspects -- Weddell Sea (Antarctica) Meteorology -- Seasonal variations Trace elements in seawater -- Southern Ocean Sea ice -- Weddell Sea (Antarctica) Biogeochemistry -- Atlantic Ocean Region Marine productivity -- Atlantic Ocean UCTD Thesis (MSc)--Stellenbosch University, 2025. Buchanan, K. 2025. Dissolved and particulate iron in the Atlantic sector marginal ice zone of the Southern Ocean. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/b123284a-b32b-459f-8198-4732a6606a7e ENGLISH ABSTRACT: Large regions of the Southern Ocean (SO), particularly the Marginal Ice Zone (MIZ), are characterised by low dissolved iron (dFe) concentrations, often limiting primary productivity. While the seasonal formation and melting of Antarctic sea ice may contribute iron (Fe) to surrounding waters, the biogeochemistry of Fe in the MIZ remains poorly constrained due to limited seasonal data, particularly in remote regions far from the Antarctic shelf. This study investigates seasonal variations in dFe and particulate Fe (pFe) in both sea ice and the surface 500m of the water column across winter and spring (2019- 2022) in the Atlantic sector of the SO, ~1200 km from the Antarctic continent. We present 53 dFe and 19 pFe measurements from 11 sea ice cores, reporting sea ice dFe concentrations ranging from below detection (0.07 nmoljkg) to 9.53 nmoljkg (mean: 0.66 ± 1.51 nmoljkg) and pFe up to 9.78 nmoljkg (mean: 3.46 ± 2.57 nmoljkg) - substantially lower than values reported in shelf-proximal studies. Distinct pFejpAl ratios suggest sea ice does not primarily source its pFe from underlying seawater, with atmospheric deposition, lateral transport, and snow contributions likely playing larger roles. Seasonal differences in seawater pFejpAl ratios, elevated in spring relative to winter, point to enhanced non-lithogenic Fe inputs-likely from biogenic material or melt-related processes. However, seawater profiles reveal that sea ice melt does not significantly elevate surface dFe concentrations during spring. Instead, dFe distributions in winter suggest vertical entrainment through mixing, while spring profiles reflect biological uptake and surface processes. A persistent decoupling between dFe and pFe, especially in spring, and the dominance of refractory pFe (with <40% in labile form) highlight the limited short-term bioavailability of pFe. Nonetheless, these particles may contribute to the long-term dFe pool through gradual remineralisation. Subsurface dFe maxima and elevated pFejpAl ratios in spring indicate a seasonal transition in Fe sources from predominantly lithogenic in winter, to melt or biologically influenced in spring. Longitudinal patterns show relatively uniform dFe across the MIZ, driven by large- scale circulation, whereas pFe exhibits greater spatial variability linked to biological activity and aggregation. Outside the MIZ, local dFe enrichment, such as at sample station WS3, suggests additional inputs possibly from hydrothermal or sedimentary sources. Fe fluxes for the Weddell Sea ice and snow concentrations were estimated to 0.69 𝜇moljm2 for dFe and 3.01 𝜇moljm2 for pFe, yielding a total Fe (TFe) flux of 3.70 𝜇moljm2 every melt season. This represents the first Fe inventory estimate for the Weddell Sea ice region to be 3.81 million mol for dFe, 16.71 million mol for pFe, totalling to 20.52 million mol of TFe. The observed values are markedly lower than previously reported inputs from sea ice, highlighting the importance of localised constrained flux estimates. Together, these results challenge assumptions of sea ice as a major Fe source and emphasise the need to distinguish between Fe fractions, recognise seasonal and spatial variability, and account for both physical and biological drivers when assessing Fe supply and productivity in the MIZ under changing sea ice regimes. AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar. Masters 2025-12-12T10:18:38Z 2025-12-12T10:18:38Z 2025-12 Thesis https://scholar.sun.ac.za/handle/10019.1/134546 en Stellenbosch University xiv, 86 pages : illustrations, maps application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Iron -- Environmental aspects -- Weddell Sea (Antarctica) Meteorology -- Seasonal variations Trace elements in seawater -- Southern Ocean Sea ice -- Weddell Sea (Antarctica) Biogeochemistry -- Atlantic Ocean Region Marine productivity -- Atlantic Ocean UCTD Buchanan, Kayla Dissolved and particulate iron in the Atlantic sector marginal ice zone of the Southern Ocean |
| title | Dissolved and particulate iron in the Atlantic sector marginal ice zone of the Southern Ocean |
| title_full | Dissolved and particulate iron in the Atlantic sector marginal ice zone of the Southern Ocean |
| title_fullStr | Dissolved and particulate iron in the Atlantic sector marginal ice zone of the Southern Ocean |
| title_full_unstemmed | Dissolved and particulate iron in the Atlantic sector marginal ice zone of the Southern Ocean |
| title_short | Dissolved and particulate iron in the Atlantic sector marginal ice zone of the Southern Ocean |
| title_sort | dissolved and particulate iron in the atlantic sector marginal ice zone of the southern ocean |
| topic | Iron -- Environmental aspects -- Weddell Sea (Antarctica) Meteorology -- Seasonal variations Trace elements in seawater -- Southern Ocean Sea ice -- Weddell Sea (Antarctica) Biogeochemistry -- Atlantic Ocean Region Marine productivity -- Atlantic Ocean UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/134546 |
| work_keys_str_mv | AT buchanankayla dissolvedandparticulateironintheatlanticsectormarginalicezoneofthesouthernocean |