Evolution of deepwater mixing and weathering inputs in the central Atlantic Ocean over the past 33 Myr
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Date
2003-12
Publication Type
Journal Article
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yes
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Abstract
The isotopic composition of Nd in present-day deep waters of the central and northeastern Atlantic Ocean is thought to fingerprint mixing of North Atlantic Deep Water with Antarctic Bottom Water. The central Atlantic Romanche and Vema Fracture Zones are considered the most important pathways for deep water exchange between the western and eastern Atlantic basins today. We present new Nd isotope records of the deepwater evolution in the fracture zones obtained from ferromanganese crusts, which are inconsistent with simple water mass mixing alone prior to 3 Ma and require additional inputs from other sources. The new Pb isotope time series from the fracture zones are inexplicable by simple mixing of North Atlantic Deep Water and Antarctic Bottom Water for the entire past 33 Myr. The distinct and relatively invariable Nd and Pb isotope records of deep waters in the fracture zones appear instead to have been controlled to a large extent by contributions from Saharan dust and the Orinoco/Amazon Rivers. Thus the previously observed similarity of Nd and Pb isotope time series from the western and eastern North Atlantic basins is better explainable by direct supply of Labrador Seawater to the eastern basin via a northern pathway rather than by advection of North Atlantic Deep Water via the Romanche and Vema Fracture Zones.
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Publication status
published
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Book title
Journal / series
Volume
18 (4)
Pages / Article No.
1091
Publisher
American Geophysical Union
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Edition / version
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Software
Geographic location
Date collected
Date created
Subject
Radiogenic isotopes; Fracture zones; North Atlantic Deep Water; Antarctic Bottom Water; Saharan dust; Labrador Sea Water
Organisational unit
03512 - Günther, Detlef / Günther, Detlef