Reconstructing past flow rates of southern component water masses using sedimentary 231Pa/230Th
<p>This thesis uses the paleoceancirculation proxy <sup>231</sup>Pa/<sup>230</sup>Th, coupled with water mass tracers δ<sup>13</sup>C and εNd, to reconstruct circulation histories for southern source waters masses in the South Atlantic, in addition to North...
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| Format: | Thesis |
| Language: | English |
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2010
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| _version_ | 1797102492849274880 |
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| author | Hickey, B |
| author2 | Henderson, G |
| author_facet | Henderson, G Hickey, B |
| author_sort | Hickey, B |
| collection | OXFORD |
| description | <p>This thesis uses the paleoceancirculation proxy <sup>231</sup>Pa/<sup>230</sup>Th, coupled with water mass tracers δ<sup>13</sup>C and εNd, to reconstruct circulation histories for southern source waters masses in the South Atlantic, in addition to North Atlantic Deep Water (NADW) far from its source, for the last ~25 kyrs.</p> <p>Downcore <sup>231</sup>Pa/<sup>230</sup>Th records from a suite of cores along a depth transect in the Argentine Basin show distinct differences with depth, suggesting that <sup>231</sup>Pa/<sup>230</sup>Th ratios in sediments are reflective of conditions in only the bottom most waters. This indicates the importance of consideration of changes in water mass distribution when interpreting <sup>231</sup>Pa/<sup>230</sup>Th records. Opal and particle flux data from these cores show little correlation with <sup>231</sup>Pa/<sup>230</sup>Th values meaning that changes in <sup>231</sup>Pa/<sup>230</sup>Th cannot be explained by a local composition or particle flux effect and are instead likely to be reflecting changes in circulation.</p> <p>A core bathed by Antarctic Intermediate Water (AAIW) throughout the last 25 kyrs (GeoB 2107, 1045 m), has relatively high <sup>231</sup>Pa/<sup>230</sup>Th values (0.075) during the Holocene and distincly lower values (0.055) at the LGM suggesting faster AAIW transport during the last glacial. At greater depths, <sup>231</sup>Pa/<sup>230</sup>Th, δ<sup>13</sup>C and εNd data in core GeoB 2109 (2504 m) indicate a change in both circulation and water mass distribution on glacial-interglacial timescales, with moderate flow of Antarctic Bottom Water (AABW) at the LGM being replaced by more vigorous flow of NADW during the Holocene. </p> <p>On millenial timescales, <sup>231</sup>Pa/<sup>230</sup>Th values in deep cores GeoB 2109 and GeoB 2112 (4010 m) indicate enhanced production of AABW during northern hemisphere stadials, when variations in <sup>231</sup>Pa/<sup>230</sup>Th records are of opposite sign between hemispheres, supporting a possible bipolar seesaw relationship in deep water formation between hemispheres. These data indicate that the <sup>231</sup>Pa/<sup>230</sup>Th proxy can be used to reconstruct past flow rates of multiple water masses in the Argentine Basin and provide evidence that southern source water masses play a dynamic counterpart to NADW formation on abrupt as well as glacial-interglacial timescales.</p> |
| first_indexed | 2024-03-07T06:06:44Z |
| format | Thesis |
| id | oxford-uuid:ee1b4b21-ffd7-4356-bbfd-4af94f01c291 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T06:06:44Z |
| publishDate | 2010 |
| record_format | dspace |
| spelling | oxford-uuid:ee1b4b21-ffd7-4356-bbfd-4af94f01c2912022-03-27T11:30:16ZReconstructing past flow rates of southern component water masses using sedimentary 231Pa/230ThThesishttp://purl.org/coar/resource_type/c_db06uuid:ee1b4b21-ffd7-4356-bbfd-4af94f01c291GeochemistryEnglishOxford University Research Archive - Valet2010Hickey, BHenderson, GThomas, A<p>This thesis uses the paleoceancirculation proxy <sup>231</sup>Pa/<sup>230</sup>Th, coupled with water mass tracers δ<sup>13</sup>C and εNd, to reconstruct circulation histories for southern source waters masses in the South Atlantic, in addition to North Atlantic Deep Water (NADW) far from its source, for the last ~25 kyrs.</p> <p>Downcore <sup>231</sup>Pa/<sup>230</sup>Th records from a suite of cores along a depth transect in the Argentine Basin show distinct differences with depth, suggesting that <sup>231</sup>Pa/<sup>230</sup>Th ratios in sediments are reflective of conditions in only the bottom most waters. This indicates the importance of consideration of changes in water mass distribution when interpreting <sup>231</sup>Pa/<sup>230</sup>Th records. Opal and particle flux data from these cores show little correlation with <sup>231</sup>Pa/<sup>230</sup>Th values meaning that changes in <sup>231</sup>Pa/<sup>230</sup>Th cannot be explained by a local composition or particle flux effect and are instead likely to be reflecting changes in circulation.</p> <p>A core bathed by Antarctic Intermediate Water (AAIW) throughout the last 25 kyrs (GeoB 2107, 1045 m), has relatively high <sup>231</sup>Pa/<sup>230</sup>Th values (0.075) during the Holocene and distincly lower values (0.055) at the LGM suggesting faster AAIW transport during the last glacial. At greater depths, <sup>231</sup>Pa/<sup>230</sup>Th, δ<sup>13</sup>C and εNd data in core GeoB 2109 (2504 m) indicate a change in both circulation and water mass distribution on glacial-interglacial timescales, with moderate flow of Antarctic Bottom Water (AABW) at the LGM being replaced by more vigorous flow of NADW during the Holocene. </p> <p>On millenial timescales, <sup>231</sup>Pa/<sup>230</sup>Th values in deep cores GeoB 2109 and GeoB 2112 (4010 m) indicate enhanced production of AABW during northern hemisphere stadials, when variations in <sup>231</sup>Pa/<sup>230</sup>Th records are of opposite sign between hemispheres, supporting a possible bipolar seesaw relationship in deep water formation between hemispheres. These data indicate that the <sup>231</sup>Pa/<sup>230</sup>Th proxy can be used to reconstruct past flow rates of multiple water masses in the Argentine Basin and provide evidence that southern source water masses play a dynamic counterpart to NADW formation on abrupt as well as glacial-interglacial timescales.</p> |
| spellingShingle | Geochemistry Hickey, B Reconstructing past flow rates of southern component water masses using sedimentary 231Pa/230Th |
| title | Reconstructing past flow rates of southern component water masses using sedimentary 231Pa/230Th |
| title_full | Reconstructing past flow rates of southern component water masses using sedimentary 231Pa/230Th |
| title_fullStr | Reconstructing past flow rates of southern component water masses using sedimentary 231Pa/230Th |
| title_full_unstemmed | Reconstructing past flow rates of southern component water masses using sedimentary 231Pa/230Th |
| title_short | Reconstructing past flow rates of southern component water masses using sedimentary 231Pa/230Th |
| title_sort | reconstructing past flow rates of southern component water masses using sedimentary 231pa 230th |
| topic | Geochemistry |
| work_keys_str_mv | AT hickeyb reconstructingpastflowratesofsoutherncomponentwatermassesusingsedimentary231pa230th |