Ba distribution in surface Southern Ocean sediments and export production estimates
| Type | Article | ||||||||
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| Date | 2002-03 | ||||||||
| Language | English | ||||||||
| Author(s) | Fagel N1, Dehairs F2, Andre L3, Bareille G4, 5, Monnin C6 | ||||||||
| Affiliation(s) | 1 : Univ Liege, Clay Mineral Dept, Liege, Belgium. 2 : Free Univ Brussels, Dept Analyt Chem, B-1050 Brussels, Belgium. 3 : Royal Museum Cent Africa, Mineral & Geochem Dept, B-3080 Tervuren, Belgium. 4 : Univ Bordeaux, Geol & Oceanog Dept, Bordeaux, France. 5 : Univ Pau & Pays Adour, CNRS, UMR 5034, LCABIE, F-64053 Pau 9, France. 6 : Univ Toulouse 3, Lab Geochem, F-31400 Toulouse, France. |
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| Source | Paleoceanography (0883-8305) (Amer Geophysical Union), 2002-03 , Vol. 17 , N. 2 , P. 1.1-1.20 | ||||||||
| DOI | 10.1029/2000PA000552 | ||||||||
| WOS© Times Cited | 21 | ||||||||
| Keyword(s) | excess Ba, sediment, Southern Ocean, export production | ||||||||
| Abstract | We present excess Ba (Baxs) data (i.e., total Ba corrected for lithogenic Ba) for surface sediments from a north-south transect between the Polar Front Zone and the northern Weddell Gyre in the Atlantic sector and between the Polar Front Zone and the Antarctic continent in the Indian sector. Focus is on two different processes that affect excess Ba accumulation in the sediments: sediment redistribution and excess Ba dissolution. The effect of these processes needs to be corrected for in order to convert accumulation rate into vertical rain rate, the flux component that can be linked to export production. In the Southern Ocean a major process affecting Ba accumulation rate is sediment focusing, which is corrected for using excess (230)Th. This correction, however, may not always be straightforward because of boundary scavenging effects. A further major process affecting excess Ba accumulation is barite dissolution during exposure at the sediment-water column interface. Export production estimates derived from excess (230)Th and barite dissolution corrected Baxs accumulation rates (i.e., excess Ba vertical rain rates) are of the same magnitude but generally larger than export production estimates based on water column proxies ((234)Th-deficit in the upper water column; particulate excess Ba enrichment in the mesopelagic water column). We believe export production values based on excess Ba vertical rain rate might be overestimated due to inaccurate assessment of the Baxs preservation rate. Barite dissolution has, in general, been taken into account by relating it to exposure time before burial depending on the rate of sediment accumulation. However, the observed decrease of excess Ba content with increasing water column depth (or increasing hydrostatic pressure) illustrates the dependence of barite preservation on degree of saturation in the deep water column in accordance with available thermodynamic data. Therefore correction for barite dissolution would not be appropriate by considering only exposure time of the barite to some uniformly undersaturated deep water but requires also that regional differences in degree of undersatuation be taken into account. | ||||||||
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