9 results found
Lambelet M, van de Flierdt T, Butler ECV, et al., 2018, The neodymium isotope fingerprint of Adélie coast bottom water, Geophysical Research Letters, Vol: 45, Pages: 11247-11256, ISSN: 0094-8276
Adélie Land Bottom Water (ALBW), a variety of Antarctic Bottom Water formed off the Adélie Land coast of East Antarctica, ventilates the abyssal layers of the Australian sector of the Southern Ocean as well as the eastern Indian and Pacific Oceans. We present the first dissolved neodymium (Nd) isotope and concentration measurements for ALBW. The summertime signature of ALBW is characterized by εNd = −8.9, distinct from Ross Sea Bottom Water, and similar to Weddell Sea Bottom Water. Adélie Land Shelf Water, the precursor water mass for wintertime ALBW, features the least radiogenic Nd fingerprint observed around Antarctica to date (εNd = −9.9). Local geology around Antarctica is important in setting the chemical signature of individual varieties of Antarctic Bottom Water, evident from the shelf water signature, which should be considered in the absence of direct wintertime observations.
van de Flierdt T, Griffiths AM, Lambelet M, et al., 2016, Neodymium in the oceans: a global database, a regional comparison and implications for palaeoceanographic research, Journal: Philosophical Transactions A: Mathematical, Physical and Engineering Sciences, Vol: 374, ISSN: 1471-2962
The neodymium (Nd) isotopic composition of seawater has been used extensively to reconstruct ocean circulation on a variety of time scales. However, dissolved neodymium concentrations and isotopes do not always behave conservatively, and quantitative deconvolution of this non-conservative component can be used to detect trace metal inputs and isotopic exchange at ocean–sediment interfaces. In order to facilitate such comparisons for historical datasets, we here provide an extended global database for Nd isotopes and concentrations in the context of hydrography and nutrients. Since 2010, combined datasets for a large range of trace elements and isotopes are collected on international GEOTRACES section cruises, alongside classical nutrient and hydrography measurements. Here, we take a first step towards exploiting these datasets by comparing high-resolution Nd sections for the western and eastern North Atlantic in the context of hydrography, nutrients and aluminium (Al) concentrations. Evaluating those data in tracer–tracer space reveals that North Atlantic seawater Nd isotopes and concentrations generally follow the patterns of advection, as do Al concentrations. Deviations from water mass mixing are observed locally, associated with the addition or removal of trace metals in benthic nepheloid layers, exchange with ocean margins (i.e. boundary exchange) and/or exchange with particulate phases (i.e. reversible scavenging). We emphasize that the complexity of some of the new datasets cautions against a quantitative interpretation of individual palaeo Nd isotope records, and indicates the importance of spatial reconstructions for a more balanced approach to deciphering past ocean changes.
Struve T, van de Flierdt T, Robinson LF, et al., 2016, Neodymium isotope analyses after combined extraction of actinide and lanthanide elements from seawater and deep-sea coral aragonite, Geochemistry Geophysics Geosystems, Vol: 17, Pages: 232-240, ISSN: 1525-2027
Isotopes of the actinide elements protactinium (Pa), thorium (Th) and uranium (U), and the lanthanide element neodymium (Nd) are often used as complementary tracers of modern and past oceanic processes. The extraction of such elements from low abundance matrices, such as seawater and carbonate, is however labor-intensive and requires significant amounts of sample material. We here present a combined method for the extraction of Pa, Th and Nd from 5 to 10 L seawater samples, and of U, Th and Nd from <1 g carbonate samples. Neodymium is collected in the respective wash fractions of Pa-Th and U-Th anion exchange chromatographies. Regardless of the original sample matrix, Nd is extracted during a two-stage ion chromatography, followed by thermal ionization mass spectrometry (TIMS) analysis as NdO+. Using this combined procedure, we obtained results for Nd isotopic compositions on two GEOTRACES consensus samples from Bermuda Atlantic Time Series (BATS), which are within error identical to results for separately sampled and processed dedicated Nd samples (εNd = -9.20 ± 0.21 and -13.11 ± 0.21 for 15 and 2000 m water depths, respectively; intercalibration results from 14 laboratories: εNd = -9.19 ± 0.57 and -13.14 ± 0.57). Furthermore, Nd isotope results for an in-house coral reference material are identical within analytical uncertainty for dedicated Nd chemistry and after collection of Nd from U-Th anion exchange chromatography. Our procedure does not require major adaptations to independently used ion exchange chromatographies for U-Pa-Th and Nd, and can hence be readily implemented for a wide range of applications.
Lambelet M, van de Flierdt T, Crocket K, et al., 2015, Neodymium isotopic composition and concentration in the western North Atlantic Ocean: results from the GEOTRACES GA02 section, Geochimica et Cosmochimica Acta, Vol: 177, Pages: 1-29, ISSN: 1872-9533
The neodymium (Nd) isotopic composition of seawater is commonly used as a proxy to study past changes in the thermohaline circulation. The modern database for such reconstructions is however poor and the understanding of the underlying processes is incomplete. Here we present new observational data for Nd isotopes and concentrations from twelve seawater depth profiles, which follow the flow path of North Atlantic Deep Water (NADW) from its formation region in the North Atlantic to the northern equatorial Atlantic. Samples were collected during two cruises constituting the northern part of the Dutch GEOTRACES transect GA02 in 2010. The results show that the different water masses in the subpolar North Atlantic Ocean, which ultimately constitute NADW, have the following Nd isotope characteristics: Upper Labrador Sea Water (ULSW), εNd = -14.2 ± 0.3; Labrador Sea Water (LSW), εNd = -13.7 ± 0.9; Northeast Atlantic Deep Water (NEADW), εNd = -12.5 ± 0.6; Northwest Atlantic Bottom Water (NWABW), εNd = -11.8 ± 1.4. In the subtropics, where these source water masses have mixed to form NADW, which is exported to the global ocean, upper-NADW is characterised by εNd values of -13.2 ± 1.0 (2sd) and lower-NADW exhibits values of εNd = -12.4 ± 0.4 (2sd). While both signatures overlap within error, the signature for lower-NADW is significantly more radiogenic than the traditionally used value for NADW (εNd = -13.5) due to the dominance of source waters from the Nordic Seas (NWABW and NEADW). Comparison between the concentration profiles and the corresponding Nd isotope profiles with other water mass properties such as salinity, silicate concentrations, neutral densities and chlorofluorocarbon (CFC) concentration provides novel insights into the geochemical cycle of Nd and reveals that different processes are necessary to account for the observed Nd characteristics in the subpolar and su
Crocket KC, Lambelet M, de Flierdt TV, et al., 2014, Measurement of fossil deep-sea coral Nd isotopic compositions and concentrations by TIMS as NdO+, with evaluation of cleaning protocols, CHEMICAL GEOLOGY, Vol: 374, Pages: 128-140, ISSN: 0009-2541
Abouchami W, Galer SJG, Horner TJ, et al., 2013, A Common Reference Material for Cadmium Isotope Studies - NIST SRM 3108, GEOSTANDARDS AND GEOANALYTICAL RESEARCH, Vol: 37, Pages: 5-17, ISSN: 1639-4488
Lambelet M, Rehkaemper M, de Flierdt TV, et al., 2013, Isotopic analysis of Cd in the mixing zone of Siberian rivers with the Arctic Ocean-New constraints on marine Cd cycling and the isotope composition of riverine Cd, EARTH AND PLANETARY SCIENCE LETTERS, Vol: 361, Pages: 64-73, ISSN: 0012-821X
Pahnke K, van de Flierdt T, Jones KM, et al., 2012, GEOTRACES intercalibration of neodymium isotopes and rare earth element concentrations in seawater and suspended particles. Part 2: Systematic tests and baseline profiles, LIMNOLOGY AND OCEANOGRAPHY-METHODS, Vol: 10, Pages: 252-269, ISSN: 1541-5856
van de Flierdt T, Pahnke K, Amakawa H, et al., 2012, GEOTRACES intercalibration of neodymium isotopes and rare earth element concentrations in seawater and suspended particles. Part 1: reproducibility of results for the international intercomparison, LIMNOLOGY AND OCEANOGRAPHY-METHODS, Vol: 10, Pages: 234-251, ISSN: 1541-5856
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