Trace elements in recent ans glacial sediments of the North Atlantic, supplement to: Willamowski, Claudia (1999): Verteilungsmuster von Spurenmetallen im glazialen Nordatlantik: Rekonstruktion der Nährstoffbilanz anhand von Cadmiumkonzentrationen in kalkschaligen Foraminiferen. GEOMAR Report, 79, 107 pp
Benthic Cd/Ca and d13C-records along sediment cores from the northern North Atlantic and the Portuguese and Moroccan continental margins are used to trace water mass distribution patterns during the last glacial with special emphasis on glacial meltwater events (‚Heinrich' events). Along the we...
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Format: | Article in Journal/Newspaper |
Language: | English |
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PANGAEA - Data Publisher for Earth & Environmental Science
1999
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Online Access: | https://dx.doi.org/10.1594/pangaea.875534 https://doi.pangaea.de/10.1594/PANGAEA.875534 |
Summary: | Benthic Cd/Ca and d13C-records along sediment cores from the northern North Atlantic and the Portuguese and Moroccan continental margins are used to trace water mass distribution patterns during the last glacial with special emphasis on glacial meltwater events (‚Heinrich' events). Along the western Iberian continental margin andin the Gulf of Cadiz, water column profiles of cadmium, calcium and phosphate are combined to retrieve a regional Cd:P-correlation which represents tracer patterns in Mediterranean Outflow Water (MOW). Benthic Cd/Ca-ratios of surface-sediment samples are used to determine modern distribution coefficients ((Cd/Ca)foraminifera:(Cd/Ca)sea water) which, in turn, are used to infer water column paleo-cadmium (Cdw) concentrations from Cd/Ca-ratios of glacial-time benthic foraminifera.Cadmium and d13C values of intermediate-water sediment cores from different areas in the northern North Atlantic are compared. Data from the upper Portuguese and upper Moroccan continental margins documenta strong MOW influence today. Modem benthic Cdw and d13C of the deeper Portuguese continental margin trace North Atlantic Deep Water (NADW), similar to benthic data from the northern North Atlantic. Glacial benthic Cd/Ca and d13C values from the upper Portuguese margin document an increased advection of glacial intermediate water (Glacial North Atlantic Intermediate Water, GNAIW; Duplessy et al., 1988), or Upper North Atlantic Deep Water (UNADW; Sarnthein et al., 1994 ). Data from the lower continental slope indicate an increased advection of Antarctic Bottom Water (AABW). At the upper Moroccan margin, glacial data are consistent with an advection of a mixture of AAIW and GNAIW/UNADW.The regional data distribution further indicates that the northern North Atlantic between 1500 and 3000 m water depth was as weil ventilated during the last glacial as today, whereas data from sediment cores from 1 to 2 km water depth imply a better glacial ventilation. Strongly reduced convection during glacial meltwater events is documented in extremely depleted benthic öl3C and enhanced Cd/Ca values at the Portuguese and Moroccan continental margins as weil as in the northern North Atlantic below 2000 water depth. At the upper Portuguese continental margin, trace metal enrichments during these events is highest. Thus, the data indicate the presence of a water mass distinctly different from glacial and modern water masses. However, the extreme enrichment of cadmium concentrations to some extent may be caused by an overprint from the sediment fraction that was released from melting icebergs and remineralized in the water column. |
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