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  • 2020-2024  (5)
Publikationsart
Schlagwörter
Verlag/Herausgeber
Erscheinungszeitraum
Jahr
  • 1
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    Characteristics, elevations and ages of various mid-late Holocene features collected from twelve islands in French Polynesia (2021)
    PANGAEA
    Details
    Publikationsdatum: 2024-01-25
    Beschreibung: Characteristics, elevations and ages of 165 samples from various mid-late Holocene features, such as in situ Porites microatolls, in situ reef flats, conglomerates and reworked reef blocks, collected from twelve islands in French Polynesia. This table complements the database on which the mid-late Holocene sea-level curve has been initially reconstructed (Hallmann et al., 2018). Δ modern-fossil represents the difference in elevation between modern and Holocene microatolls at the same study site and in a similar environment (maximum vertical error is of ± 2 cm). NGPF = altimetric reference of French Polynesia. The elevations have been corrected for subsidence based on rates of 0.14 mm/yr for Moorea, 0.05 mm/yr for Bora Bora and Tahaa as well as 0.03 mm/yr for Maupiti, the Gambier Islands and Raivavae. Error values for ages and elevations are 2-sigma. Uncertainties for measured elevations related to NGPF are ± 14 cm for samples from Bora Bora, Maupiti, Raivavae, Tikehau and the Gambier Islands; ± 22 cm for samples from Fakarava, Hao, Makemo, Manihi, Moorea, Rangiroa and Tahaa. Uncertainties for estimated elevations are ± 10 cm for Δ modern-fossil and ± 22 cm for NGPF elevations.
    Schlagwort(e): AGE; Age, dated standard deviation; Aragonite; Bora Bora; Calculated; Corrected; Diameter; Difference; ELEVATION; Event label; Fakarava; French_Polynesia_BOB; French_Polynesia_FAK; French_Polynesia_GAM; French_Polynesia_HAO; French_Polynesia_MAK; French_Polynesia_MAN; French_Polynesia_MAU; French_Polynesia_MOO; French_Polynesia_RAI; French_Polynesia_RAN; French_Polynesia_TAA; French_Polynesia_TIK; French Polynesia; Gambier; HAND; Hao; LATITUDE; Location; LONGITUDE; low-lying islands; Makemo; Manihi; Maupiti; mid-late Holocene sea level; Moorea; Porites microatolls; Raivavae; Rangiroa; reef development; Sample comment; Sample ID; Sampling by hand; storm deposits; Tahaa; Tikhau; U-series dating
    Materialart: Dataset
    Format: text/tab-separated-values, 1068 data points
    Standort Signatur Einschränkungen Verfügbarkeit
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    DATA PANGAEA
  • 2
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    Uranium/Thorium isotopic composition of various mid-late Holocene features collected from twelve islands in French Polynesia (2021)
    PANGAEA
    Details
    Publikationsdatum: 2024-01-25
    Beschreibung: Uranium/Thorium isotopic composition of 165 samples from various mid-late Holocene features, such as in situ Porites microatolls, in situ reef flats, conglomerates and reworked reef blocks, collected from twelve islands in French Polynesia. Recommendations of Dutton et al. (2017) were followed for the presentation of U/Th age data. For each parameter, the first column contains the value and the second column the statistical error. All statistical errors are two standard deviations of the mean (2σ mean). All samples have been corrected for initial 230Th by using a 230Th/232Th activity ratio of 0.66 ± 0.2 (Fietzke et al., 2005). Non-reported data consist of 230Th/232Th ratios which became negative due to background corrections. 238U Concentrations are not corrected for the background.
    Schlagwort(e): Age, dated; Age, dated standard deviation; Age, Uranium-Thorium; Bora Bora; Calculated; Event label; Fakarava; French_Polynesia_BOB; French_Polynesia_FAK; French_Polynesia_GAM; French_Polynesia_HAO; French_Polynesia_MAK; French_Polynesia_MAN; French_Polynesia_MAU; French_Polynesia_MOO; French_Polynesia_RAI; French_Polynesia_RAN; French_Polynesia_TAA; French_Polynesia_TIK; French Polynesia; Gambier; HAND; Hao; LATITUDE; LONGITUDE; low-lying islands; Makemo; Manihi; Maupiti; mid-late Holocene sea level; Moorea; Porites microatolls; Raivavae; Rangiroa; reef development; Sample ID; Sampling by hand; storm deposits; Tahaa; Thorium-230; Thorium-230, standard deviation; Thorium-230/Thorium-232 activity ratio; Thorium-230/Thorium-232 activity ratio, standard deviation; Thorium-230/Uranium-238 activity ratio; Thorium-230/Uranium-238 activity ratio, error, relative; Thorium-232; Thorium-232, standard deviation; Tikhau; Uranium-234/Uranium-238 activity ratio; Uranium-234/Uranium-238 activity ratio, standard deviation; Uranium-238; Uranium-238, standard deviation; Uranium-238/Thorium-232 activity ratio; Uranium-238/Thorium-232 activity ratio, standard deviation; U-series dating
    Materialart: Dataset
    Format: text/tab-separated-values, 3111 data points
    Standort Signatur Einschränkungen Verfügbarkeit
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    DATA PANGAEA
  • 3
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    Inverse response of 231Pa/230Th to variations of the Atlantic meridional overturning circulation in the North Atlantic intermediate water (2020)
    Springer
    Details
    Publikationsdatum: 2023-02-08
    Beschreibung: This study aims to provide a more detailed understanding of the behavior of 231Pa/230Th under varying ocean circulation regimes. The North Atlantic provides a unique sedimentary setting with its ice-rafted detritus (IRD) layers deposited during glacial times. These layers have been found north of 40° N (Ruddiman Belt) and are most pronounced during Heinrich Stadials. Most of these sediments have been recovered from the deep North Atlantic basin typically below 3000 m water depth. This study reports sedimentological and sediment geochemical data from one of the few sites at intermediate depth of the open North Atlantic (core SU90-I02, 45° N 39° W, 1965 m water depth) within the Ruddiman Belt. The time periods of Heinrich Stadials 1 and 2 of this core were identified with the help of the major element composition by XRF scanning and by IRD counting. Along the core profile, the sedimentary 231Pa/230Th activity ratio has been measured as a kinematic proxy for the circulation strength. The 231Pa/230Th record shows highest values during the Holocene and Last Glacial Maximum, above the natural production ratio of these isotopes. During Heinrich Stadials 1 and 2, when Atlantic meridional overturning circulation was most reduced, the 231Pa/230Th record shows overall lowest values below the production ratio. This behavior is contrary to classical findings of 231Pa/230Th from the northwestern Atlantic where a strong Holocene circulation is associated with low values. However, this behavior at the presented location is in agreement with results from simulations of the 231Pa/230Th-enabled Bern3D Earth system model.
    Materialart: Article , PeerReviewed
    Format: text
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    Format: other
    Standort Signatur Einschränkungen Verfügbarkeit
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    OceanRep: Artikel in einer Fachzeitschrift - begutachtet
  • 4
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    Minimal cobalt metabolism in the marine cyanobacterium Prochlorococcus (2020)
    National Academy of Sciences (Washington, DC)
    Details
    Publikationsdatum: 2023-02-08
    Beschreibung: Despite very low concentrations of cobalt in marine waters, cyanobacteria in the genus Prochlorococcus retain the genetic machinery for the synthesis and use of cobalt-bearing cofactors (cobalamins) in their genomes. We explore cobalt metabolism in a Prochlorococcus isolate from the equatorial Pacific Ocean (strain MIT9215) through a series of growth experiments under iron- and cobalt-limiting conditions. Metal uptake rates, quantitative proteomic measurements of cobalamin-dependent enzymes, and theoretical calculations all indicate that Prochlorococcus MIT9215 can sustain growth with less than 50 cobalt atoms per cell, ∼100-fold lower than minimum iron requirements for these cells (∼5,100 atoms per cell). Quantitative descriptions of Prochlorococcus cobalt limitation are used to interpret the cobalt distribution in the equatorial Pacific Ocean, where surface concentrations are among the lowest measured globally but Prochlorococcus biomass is high. A low minimum cobalt quota ensures that other nutrients, notably iron, will be exhausted before cobalt can be fully depleted, helping to explain the persistence of cobalt-dependent metabolism in marine cyanobacteria.
    Materialart: Article , PeerReviewed
    Format: text
    Format: text
    Standort Signatur Einschränkungen Verfügbarkeit
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    OceanRep: Artikel in einer Fachzeitschrift - begutachtet
  • 5
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    Living on the edge: environmental variability of a shallow late Holocene cold-water coral mound (2022)
    Springer
    Details
    Publikationsdatum: 2024-02-07
    Beschreibung: Similar to their tropical counterparts, cold-water corals (CWCs) are able to build large three-dimensional reef structures. These unique ecosystems are at risk due to ongoing climate change. In particular, ocean warming, ocean acidification and changes in the hydrological cycle may jeopardize the existence of CWCs. In order to predict how CWCs and their reefs or mounds will develop in the near future one important strategy is to study past fossil CWC mounds and especially shallow CWC ecosystems as they experience a greater environmental variability compared to other deep-water CWC ecosystems. We present results from a CWC mound off southern Norway. A sediment core drilled from this relatively shallow (~ 100 m) CWC mound exposes in full detail hydrographical changes during the late Holocene, which were crucial for mound build-up. We applied computed tomography, 230Th/U dating, and foraminiferal geochemical proxy reconstructions of bottom-water-temperature (Mg/Ca-based BWT), δ18O for seawater density, and the combination of both to infer salinity changes. Our results demonstrate that the CWC mound formed in the late Holocene between 4 kiloannum (ka) and 1.5 ka with an average aggradation rate of 104 cm/kiloyears (kyr), which is significantly lower than other Holocene Norwegian mounds. The reconstructed BWTMg/Ca and seawater density exhibit large variations throughout the entire period of mound formation, but are strikingly similar to modern in situ observations in the nearby Tisler Reef. We argue that BWT does not exert a primary control on CWC mound formation. Instead, strong salinity and seawater density variation throughout the entire mound sequence appears to be controlled by the interplay between the Atlantic Water (AW) inflow and the overlying, outflowing Baltic-Sea water. CWC growth and mound formation in the NE Skagerrak was supported by strong current flow, oxygen replenishment, the presence of a strong boundary layer and larval dispersal through the AW, but possibly inhibited by the influence of fresh Baltic Water during the late Holocene. Our study therefore highlights that modern shallow Norwegian CWC reefs may be particularly endangered due to changes in water-column stratification associated with increasing net precipitation caused by climate change.
    Materialart: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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    Standort Signatur Einschränkungen Verfügbarkeit
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    OceanRep: Artikel in einer Fachzeitschrift - begutachtet
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