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  • Climate - Biogeochemistry Interactions in the Tropical Ocean; SFB754  (4)
  • Paleoflux  (2)
  • neodymium isotopes  (2)
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  • 1
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    Authigenic and Detrital Carbonate Nd Isotope Records Reflect Pulses of Detrital Material Input to the Labrador Sea During the Heinrich Stadials (2023)
    Details
    Publication Date: 2023-07-19
    Description: Limited constraints on the variability of the deep‐water production in the Labrador Sea complicate reconstructions of the strength of the Atlantic Meridional Overturning Circulation (AMOC) during the Late Quaternary. Large volumes of detrital carbonates were repeatedly deposited in the Labrador Sea during the last 32 kyr, potentially affecting radiogenic Nd isotope signatures. To investigate this the Nd isotope compositions of deep and intermediate waters were extracted from the authigenic Fe‐Mn oxyhydroxide fraction, foraminiferal coatings, the residual silicates and leachates of dolostone grains. We provide a first order estimation of Nd release via dissolution of detrital carbonates and its contribution to the authigenic ԑNd signatures in the Labrador Sea. During the Last Glacial Maximum the Nd isotope signatures in the Labrador Sea would allow active water mass mixing with more radiogenic ɛNd values (−12.6 and −14) prevailing in its eastern part whereas less radiogenic values (ɛNd ∼ −18.4) were found on the western Labrador slope. The deposition of detrital carbonates during Heinrich stadials (2,1) was accompanied by negative detrital and authigenic Nd isotope excursions (ɛNd ∼ −31) that were likely controlled by dissolution of dolostone or dolostone associated mineral inclusions. This highly unradiogenic signal dominated the authigenic phases and individual water masses in the Labrador Sea, serving as potential source of highly unradiogenic Nd to the North Atlantic region, while exported southward. The Holocene authigenic ɛNd signatures of the coatings and leachates significantly differed from those of the detrital silicates, approaching modern bottom water mass signatures during the Late Holocene.
    Description: Plain Language Summary: The Labrador Sea is an important region for deep water formation and for the ocean circulation in the Atlantic region. Over the last 32 thousand years, numerous discharges from melting glaciers added freshwater to the Labrador Sea which could help understand the future effects of current melting glaciers. This information is necessary to better constrain climate predictions in order to gauge the effects on the Global Ocean Water Circulation. However, past deep water production in the Labrador is still poorly constrained, complicating reconstruction of the Atlantic Meridional Overturning Circulation on different timescales. In this study we investigated changes in deep and intermediate water mass circulation patterns over the last 32 kyr based on the radiogenic Nd isotope compositions that serve as a water mass circulation proxy. Analysis of four marine sediment cores show that the deposition of large volumes of detrital carbonates during studied period had a large effect on the recorded in the sediment column signals. New data suggest active water mass circulation during the maximum extent of glacial ice sheets. The modern day ocean circulation patterns have emerged during the Late Holocene (6 ka).
    Description: Key Points: Estimation of Nd release via dissolution of detrital carbonates and its contribution to the authigenic ԑNd signatures in the Labrador Sea. Dissolution of detrital dolostones in the water column during Heinrich stadials at least partially controlled ɛNd signatures. During the LGM generally more radiogenic signatures possibly indicate active water mass advection and mixing in the Labrador Sea.
    Description: GEOMAR Helmholtz‐Zentrum für Ozeanforschung Kiel http://dx.doi.org/10.13039/501100003153
    Description: Kiel University
    Description: https://doi.org/10.1594/PANGAEA.952659
    Keywords: ddc:551.9 ; Labrador Sea ; Late Quaternary ; Paleoceanography ; neodymium isotopes ; dolostone ; AMOC ; carbonate dissolution ; Heinrich stadials
    Language: English
    Type: doc-type:article
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    CITATION GEO-LEO
  • 2
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    Th-230 normalization : an essential tool for interpreting sedimentary fluxes during the late Quaternary (2010)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 19 (2004): PA1018, doi:10.1029/2003PA000939.
    Description: There is increasing evidence indicating that syndepositional redistribution of sediment on the seafloor by bottom currents is common and can significantly affect sediment mass accumulation rates. Notwithstanding its common incidence, this process (generally referred to as sediment focusing) is often difficult to recognize. If redistribution is near synchronous to deposition, the stratigraphy of the sediment is not disturbed and sediment focusing can easily be overlooked. Ignoring it, however, can lead to serious misinterpretations of sedimentary fluxes, particularly when past changes in export flux from the overlying water are inferred. In many instances, this problem can be resolved, at least for sediments deposited during the late Quaternary, by normalizing to the flux of 230Th scavenged from seawater, which is nearly constant and equivalent to the known rate of production of 230Th from the decay of dissolved 234U. We review the principle, advantages and limitations of this method. Notwithstanding its limitations, it is clear that 230Th normalization does provide a means of achieving more accurate interpretations of sedimentary fluxes and eliminates the risk of serious misinterpretations of sediment mass accumulation rates.
    Description: R. Francois and M. P. Bacon acknowledge support from the National Science Foundation. M. Frank thanks the Swiss Science Foundation for support.
    Keywords: Paleoflux ; Sediment focusing ; Paleoproductivity
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 3
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    Neodymium isotopes trace marine provenance of Arctic sea ice (2022)
    European Association of Geochemistry
    Details
    Publication Date: 2022-10-12
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Laukert, G., Peeken, I., Bauch, D., Krumpen, T., Hathorne, E. C., Werner, K., Gutjahr, M., & Frank, M. Neodymium isotopes trace marine provenance of Arctic sea ice. Geochemical Perspectives Letters, 22, (2022): 10–15, https://doi.org/10.7185/geochemlet.2220.
    Description: Radiogenic neodymium (Nd) isotopes (ɛNd) have the potential to serve as a geochemical tracer of the marine origin of Arctic sea ice. This capability results from pronounced ɛNd differences between the distinct marine and riverine sources, which feed the surface waters from which the ice forms. The first dissolved Nd isotope and rare earth element (REE) concentration data obtained from Arctic sea ice collected across the Fram Strait during RV Polarstern cruise PS85 in 2014 confirm the incorporation and preservation of the parental surface seawater ɛNd signatures despite efficient REE rejection. The large ɛNd variability between ice floes and within sea ice cores (−32 to −10) reflects changes in water mass distribution during ice growth and drift from the central Arctic Ocean to Fram Strait. In addition to the parental seawater composition, our new approach facilitates the reconstruction of the transfer of matter between the atmosphere, the sea ice and the ocean. In conjunction with satellite-derived drift trajectories, we enable a more accurate assessment of sea ice origin and spatiotemporal evolution, benefiting studies of sea ice biology, biodiversity, and biogeochemistry.
    Description: We acknowledge financial support by the German Federal Ministry of Education and Research (Grant BMBF 03F0776 and 03G0833) and the Ministry of Education and Science of the Russian Federation. GL also acknowledges financial support from the Ocean Frontier Institute through an award from the Canada First Research Excellence Fund.
    Keywords: Arctic Ocean ; Fram Strait ; Greenland ; Transpolar Drift ; Siberian Shelf ; sea ice ; snow ; seawater ; provenance tracers ; neodymium isotopes ; oxygen isotopes ; rare earth elements ; water masses ; circulation
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
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    Comment on “Do geochemical estimates of sediment focusing pass the sediment test in the equatorial Pacific?” by M. Lyle et al. (2010)
    American Geophysical Union
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 22 (2007): PA1216, doi:10.1029/2005PA001235.
    Keywords: Paleoflux ; Th-230
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 5
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    Distribution of neodymium isotopes and concentrations during M77/3 and M77/4 (2013)
    PANGAEA
    In:  Supplement to: Grasse, Patricia; Stichel, Torben; Stumpf, Roland; Stramma, Lothar; 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, 198-207, https://doi.org/10.1016/j.epsl.2012.07.044
    Details
    Publication Date: 2023-10-28
    Description: 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 11400N and 161S 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 (eNd=-2). Surface waters in the northernmost part of the study area are even more radiogenic (eNd = +3), most likely due to release of Nd from volcanogenic material. Deep and bottom waters at the southernmost offshore station (141S) are clearly controlled by advection of water masses with less radiogenic signatures (eNd=- 7) originating from the Southern Ocean. Towards the equator, however, the deep waters show a clear trend towards more radiogenic values of up to eNd=-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.
    Keywords: Climate - Biogeochemistry Interactions in the Tropical Ocean; SFB754
    Type: Dataset
    Format: application/zip, 2 datasets
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    DATA PANGAEA
  • 6
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    14C and age models for cores M772-052 and M772-029; diatom assemblages and biogenic opal and organic carbon data (2017)
    PANGAEA
    In:  Supplement to: Doering, Kristin; Erdem, Zeynep; Ehlert, Claudia; Fleury, Sophie; Frank, Martin; Schneider, Ralph R (2016): Changes in diatom productivity and upwelling intensity off Peru since the Last Glacial Maximum: Response to basin-scale atmospheric and oceanic forcing. Paleoceanography, 31(10), 1453-1473, https://doi.org/10.1002/2016PA002936
    Details
    Publication Date: 2023-10-28
    Description: New records of stable silicon isotope signatures (?30Si) together with concentrations of biogenic opal and organic carbon from the central (9°S) and northern (5°S) Peruvian margin reveal changes in diatom productivity and nutrient utilization during the past 20,000 years. The findings are based on a new approach using the difference between the ?30Si signatures of small (11-32 ?m) and large (〉150 ?m) diatom fractions (?30Si ) in combination with the variance in diatom assemblages for reconstruction Coscino-bSi of past upwelling intensity. Combination of our records with two previously published records from the southern upwelling area off Peru (12-15°S) shows a general decoupling of the environmental conditions at the central and southern shelf mainly caused by a northward shift of the main upwelling cell from its modern position (12-15°S) toward 9°S during Termination 1. At this time only moderate upwelling intensity and productivity levels prevailed between 9°S and 12°S interpreted by a more northerly position of Southern Westerly Winds and the South Pacific Subtropical High. Furthermore, a marked decrease in productivity at 12-15°S during Heinrich Stadial 1 coincided with enhanced biogenic opal production in the Eastern Equatorial Pacific, which was induced by a southward shift of the Intertropical Convergence Zone and enhanced northeasterly trade winds. Modern conditions were only established at the onset of the Holocene. Past changes in preformed ?30Si signatures of subsurface waters reaching the Peruvian Upwelling System did not significantly affect the preserved ?30Si signatures
    Keywords: Climate - Biogeochemistry Interactions in the Tropical Ocean; SFB754
    Type: Dataset
    Format: application/zip, 7 datasets
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    DATA PANGAEA
  • 7
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    Age models for sediment cores M77/1-470-MUC29, M77/1-449-MUC19 and M77/1-459-MUC53 from the Peruvian shelf at 11°S (2016)
    PANGAEA
    In:  Supplement to: Ehlert, Claudia; Doering, Kristin; Wallmann, Klaus; Scholz, Florian; Sommer, Stefan; Grasse, Patricia; Geilert, Sonja; Frank, Martin (2016): Stable silicon isotope signatures of marine pore waters – Biogenic opal dissolution versus authigenic clay mineral formation. Geochimica et Cosmochimica Acta, 191, 102-117, https://doi.org/10.1016/j.gca.2016.07.022
    Details
    Publication Date: 2023-10-28
    Description: Dissolved silicon isotope compositions have been analysed for the first time in pore waters (δ30SiPW) of three short sediment cores from the Peruvian margin upwelling region with distinctly different biogenic opal content in order to investigate silicon isotope fractionation behaviour during early diagenetic turnover of biogenic opal in marine sediments. The δ30SiPW varies between +1.1‰ and +1.9‰ with the highest values occurring in the uppermost part close to the sediment–water interface. These values are of the same order or higher than the δ30Si of the biogenic opal extracted from the same sediments (+0.3‰ to +1.2‰) and of the overlying bottom waters (+1.1‰ to +1.5‰). Together with dissolved silicic acid concentrations well below biogenic opal saturation, our collective observations are consistent with the formation of authigenic alumino-silicates from the dissolving biogenic opal. Using a numerical transport-reaction model we find that approximately 24% of the dissolving biogenic opal is re-precipitated in the sediments in the form of these authigenic phases at a relatively low precipitation rate of 56 μmol Si cm−2 yr−1. The fractionation factor between the precipitates and the pore waters is estimated at −2.0‰. Dissolved and solid cation concentrations further indicate that off Peru, where biogenic opal concentrations in the sediments are high, the availability of reactive terrigenous material is the limiting factor for the formation of authigenic alumino-silicate phases.
    Keywords: Climate - Biogeochemistry Interactions in the Tropical Ocean; SFB754
    Type: Dataset
    Format: application/zip, 6 datasets
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    DATA PANGAEA
  • 8
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    Dissolved rare earth elements and neodymium isotopes from water samples during METEOR cruise M90 (2018)
    PANGAEA
    In:  Supplement to: Grasse, Patricia; Bosse, Michael; Hathorne, Ed C; Böning, Philipp; Pahnke, Katharina; Frank, Martin (2017): Short-term variability of dissolved rare earth elements and neodymium isotopes in the entire water column of the Panama Basin. Earth and Planetary Science Letters, 475, 242-253, https://doi.org/10.1016/j.epsl.2017.07.022
    Details
    Publication Date: 2023-12-09
    Description: The distribution of dissolved rare earth elements (REEs) and neodymium isotopes (εNd) in the open ocean traces water mass mixing and provides information on lithogenic inputs to the source regions of the water masses. However, the processes influencing the REE budget at the ocean margins, in particular source and sink mechanisms, are not yet well quantified. In this study the first dissolved REE concentrations and Nd isotope compositions of seawater from the Panama Basin (RV Meteor cruise M90) in the Eastern Equatorial Pacific (EEP) are presented.
    Keywords: Climate - Biogeochemistry Interactions in the Tropical Ocean; SFB754
    Type: Dataset
    Format: application/zip, 2 datasets
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    DATA PANGAEA
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