The distribution of neodymium isotopes and concentrations in the Eastern Equatorial Pacific: Water mass advection versus particle exchange.

Grasse, Patricia , Stichel, Torben, Stumpf, Roland, Stramma, Lothar and Frank, Martin (2012) The distribution of neodymium isotopes and concentrations in the Eastern Equatorial Pacific: Water mass advection versus particle exchange. Earth and Planetary Science Letters, 353/354 . pp. 198-207. DOI 10.1016/j.epsl.2012.07.044.

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Abstract

The radiogenic isotope composition of the Rare Earth Element (REE) neodymium (Nd) is a powerful water mass proxy for present and past ocean circulation. The processes controlling the Nd budget of the global ocean are not quantitatively understood and in particular source and sink mechanisms are still under debate.

In this study we present the first full water column data set of dissolved Nd isotope compositions and Nd concentrations for the Eastern Equatorial Pacific (EEP), where one of the globally largest Oxygen Minimum Zones (OMZ) is located. This region is of particular interest for understanding the biogeochemical cycling of REEs because anoxic conditions may lead to release of REEs from the shelf, whereas high particle densities and fluxes potentially remove the REEs from the water column. Data were obtained between 1°40′N and 16°S along a nearshore and an offshore transect. Near surface zonal current bands, such as the Equatorial Undercurrent (EUC) and the Subsurface Countercurrent (SSCC), which are supplying oxygen-rich water to the OMZ are characterized by radiogenic Nd isotope signatures (εNd=−2). Surface waters in the northernmost part of the study area are even more radiogenic (εNd=+3), most likely due to release of Nd from volcanogenic material. Deep and bottom waters at the southernmost offshore station (14°S) are clearly controlled by advection of water masses with less radiogenic signatures (εNd=−7) originating from the Southern Ocean. Towards the equator, however, the deep waters show a clear trend towards more radiogenic values of up to εNd=−2. The northernmost station located in the Panama basin shows highly radiogenic Nd isotope signatures in the entire water column, which indicates that particle scavenging, downward transport and release processes play an important role. This is supported by relatively low Nd concentrations in deep waters (3000–6000 m) in the EEP (20 pmol/kg) compared to locations in the Northern and Central Pacific (40–60 pmol/kg), which suggests enhanced removal of Nd in the EEP.

Document Type: Article
Additional Information: WOS:000311014300021
Keywords: Neodymium isotopes; Rare Earth Elements; particle scavenging; boundary exchange; oxygen minimum zone; Eastern Equatorial Pacific; RARE-EARTH-ELEMENTS; GENERAL-CIRCULATION MODEL; OCEAN CIRCULATION; NORTH PACIFIC; TROPICAL PACIFIC; MEDITERRANEAN-SEA; ND-ISOTOPES; PORE WATERS; PERU; SEAWATER
Research affiliation: OceanRep > SFB 754
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
OceanRep > SFB 754 > A5
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-PO Physical Oceanography
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.epsl.2012.07.044
ISSN: 0012-821X
Projects: SFB754, Future Ocean
Expeditions/Models/Experiments:
Date Deposited: 24 Sep 2012 08:57
Last Modified: 23 Sep 2019 17:44
URI: http://oceanrep.geomar.de/id/eprint/15346

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