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  • 2020-2024  (44)
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  • 1
    Publication Date: 2024-02-07
    Description: In this study, we used stable isotopes of oxygen (δ18O), deuterium (δD), and dissolved inorganic carbon (δ13CDIC) in combination with temperature, salinity, oxygen and nutrient concentrations to characterize the coastal (71-78 °W) and an oceanic (82-98 °W) water masses (SAAW-Subantarctic Surface Water; STW-Subtropical Water; ESSW-Equatorial Subsurface water; AAIW-Antarctic Intermediate Water; PDW-Pacific Deep Water) of the Southeast Pacific (SEP). The results show that δ18O and δD can be used to differentiate between SAAW-STW, SAAW-ESSW and ESSW-AAIW. δ13CDIC signatures can be used to differentiate between STW-ESSW (oceanic section), SAAW-ESSW, ESSW-AAIW and AAIW-PDW. Compared with the oceanic section, our new coastal section highlights differences in both the chemistry and geometry of water masses above 1000 m. Previous paleoceanographic studies using marine sediments from the SEP continental margin used the present-day hydrological oceanic transect to compare against, as the coastal section was not sufficiently characterized. We suggest that our new results of the coastal section should be used for past characterizations of the SEP water masses that are usually based on continental margin sediment samples.
    Type: Article , PeerReviewed
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  • 2
    Publication Date: 2024-02-07
    Description: We present a global atlas of downcore foraminiferal oxygen and carbon isotope ratios available at https://doi.org/10.1594/PANGAEA.936747 (Mulitza et al., 2021a). The database contains 2106 published and previously unpublished stable isotope downcore records with 361 949 stable isotope values of various planktic and benthic species of Foraminifera from 1265 sediment cores. Age constraints are provided by 6153 uncalibrated radiocarbon ages from 598 (47 %) of the cores. Each stable isotope and radiocarbon series is provided in a separate netCDF file containing fundamental metadata as attributes. The data set can be managed and explored with the free software tool PaleoDataView. The atlas will provide important data for paleoceanographic analyses and compilations, site surveys, or for teaching marine stratigraphy. The database can be updated with new records as they are generated, providing a live ongoing resource into the future.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 3
    Publication Date: 2024-03-22
    Description: Paleoceanographic reconstructions show that the strength of North Atlantic currents decreased during the Little Ice Age. In contrast, the role of ocean circulation in climate regulation during earlier historical epochs of the Common Era (C.E.) remains unclear. Here, we reconstruct sea surface temperature (SST) and salinity in the Caribbean Basin for the past 1700 years using the isotopic and elemental composition of planktic foraminifera tests. Centennial-scale SST and salinity variations in the Caribbean co-occur with (hydro)climate changes in the Northern Hemisphere and are linked to a North Atlantic SST forcing. Cold phases around 600, 800, and 1400 to 1600 C.E. are characterized by Caribbean salinification and Gulf of Mexico freshening that implies reductions in the strength of North Atlantic surface circulation. We suggest that the associated changes in the meridional salt advection contributed to the historical climate variability of the C.E.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 4
    Publication Date: 2023-05-31
    Description: To identify environmental causes for past changes in vegetation in subtropical East Asia, we present carbon isotope compositions of plant-wax n-alkanes and provide estimates of the C4-plant contribution across the past four glacial terminations and interglacials, based on cores recovered from the northern South China Sea. Our results show a comparable C4-plant contribution between the Last Glacial Maximum (LGM) and the Holocene. An increase of the C4-plant contribution by 15–20% is found for Terminations IV, II and I relative to subsequent interglacial peaks, coeval with an expansion of Cyperaceae and Poaceae. In contrast, Termination V reveals a lower C4-plant contribution than Marine Isotope Stage (MIS) 11c. The data exhibit a long-term trend, with a stepwise increase of the C4-plant contribution across interglacials MIS 11c, 9e, 7e and 1. We suggest that no substantial changes in humidity levels over glacial-interglacial cycles occurred facilitating a similar C3/C4-plant ratio for the LGM and the Holocene. Instead, deglacial sea-level rises caused an extensive development of floodplains and wetlands on the exposed continental shelf, providing habitats for the spread of C4 sedges and grasses. The progressive subsidence of Chinese coastal areas and the broadening of the continental shelf over the late Quaternary explains the nearly absence of C4 plant occurrence during Termination V and a gradual increase of the C4-plant contribution across interglacial peaks. Taken together, changes in coastal environments should be considered when interpreting marine-based vegetation reconstructions from subtropical Asia.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
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  • 5
    Publication Date: 2024-01-31
    Description: In this study, we used stable isotopes of oxygen (δ18O), deuterium (δD), and dissolved inorganic carbon (δ13CDIC) in combination with temperature, salinity, oxygen, and nutrient concentrations to characterize the coastal (71°–78°W) and an oceanic (82°–98°W) water masses (SAAW—Subantarctic Surface Water; STW—Subtropical Water; ESSW—Equatorial Subsurface water; AAIW—Antarctic Intermediate Water; PDW—Pacific Deep Water) of the Southeast Pacific (SEP). The results show that δ18O and δD can be used to differentiate between SAAW-STW, SAAW-ESSW, and ESSW-AAIW. δ13CDIC signatures can be used to differentiate between STW-ESSW (oceanic section), SAAW-ESSW, ESSW-AAIW, and AAIW-PDW. Compared with the oceanic section, our new coastal section highlights differences in both the chemistry and geometry of water masses above 1,000 m. Previous paleoceanographic studies using marine sediments from the SEP continental margin used the present-day hydrological oceanic transect to compare against, as the coastal section was not sufficiently characterized. We suggest that our new results of the coastal section should be used for past characterizations of the SEP water masses that are usually based on continental margin sediment samples.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
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  • 6
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    American Geophysical Union (AGU)
    In:  EPIC3Geophysical Research Letters, American Geophysical Union (AGU), 49(24), ISSN: 0094-8276
    Publication Date: 2024-03-13
    Description: The East Australian Current (EAC) is the western boundary current of the South Pacific Subtropical Gyre that transports warm tropical waters to higher southern latitudes and significantly impacts the climate of Australia and New Zealand. Modern observations show that the EAC has strengthened with rising global temperatures. However, little is known about the pre-industrial variability of the EAC and the forcing mechanisms. Planktic foraminifera Globigerinoides ruber (white) Mg/Ca-based sea surface temperature reconstructions offshore northeastern Australia between 15° and 26°S reveal an increase by ∼1.2°C after ∼1400 CE. We infer that the increase in temperature is related to a stronger EAC heat transport that is likely driven by a strengthening of the Southern Hemisphere subtropical gyre circulation due to a progressive shift of the Southern annular mode toward its positive phase and of El Niño-Southern Oscillation toward more El Niño-like conditions.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 7
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    American Association for the Advancement of Science (AAAS)
    In:  EPIC3Science Advances, American Association for the Advancement of Science (AAAS), 9(44), pp. eadg2639-eadg2639, ISSN: 2375-2548
    Publication Date: 2024-04-24
    Description: Paleoceanographic reconstructions show that the strength of North Atlantic currents decreased during the Little Ice Age. In contrast, the role of ocean circulation in climate regulation during earlier historical epochs of the Common Era (C.E.) remains unclear. Here, we reconstruct sea surface temperature (SST) and salinity in the Caribbean Basin for the past 1700 years using the isotopic and elemental composition of planktic foraminifera tests. Centennial-scale SST and salinity variations in the Caribbean co-occur with (hydro)climate changes in the Northern Hemisphere and are linked to a North Atlantic SST forcing. Cold phases around 600, 800, and 1400 to 1600 C.E. are characterized by Caribbean salinification and Gulf of Mexico freshening that implies reductions in the strength of North Atlantic surface circulation. We suggest that the associated changes in the meridional salt advection contributed to the historical climate variability of the C.E.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
    Format: application/pdf
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  • 8
    Publication Date: 2023-01-30
    Description: This data set contains a compilation of records of sea-surface and thermocline temperatures, derived from planktonic foraminifera Mg/Ca, for the Indo-Pacific Warm Pool (ranges 14.8°N-13.1°S, 115.2°E-158.0°E) over the past 25,000 years. It contains two sets of data-sheets (six sheets). Set 1: the mean anomaly stacks of sea-surface temperature anomaly )(SSTA, sheet 1), thermocline water temperature anomaly (TWTA, sheet 2), oxygen isotope composition of Globigerinoides ruber (Gr-A, sheet 3) and surface water oxygen isotope composition (Δδ18Osw, sheet 4) of IPWP over the last 25 ka. Set 2: the records of Mg/Ca and calibrated temperatures of Cores MD10-3340 (0.52°S, 128.72°E, sheet 5), SO18480 (12.06°S, 121.65°E, sheet 6) and KX21-2 (1.42°S, 157.98°E, sheet 7) firstly reported in this study.
    Keywords: Deglaciation; Holocene; Indo-Pacific Warm Pool; LGM; Thermocline
    Type: Dataset
    Format: application/zip, 4 datasets
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  • 9
    Publication Date: 2023-01-30
    Description: As reverse weathering has been shown to impact long-term changes in atmospheric CO2 levels, it is crucial to develop quantitative tools to reconstruct marine authigenic clay formation. We explored the potential of the beryllium (Be) isotope ratio (10Be/9Be) recorded in marine clay-sized sediment to track neoformation of authigenic clays. The power of such proxy relies on the orders-of-magnitude difference in 10Be/9Be ratios between continental Be and Be dissolved in seawater. On riverine and marine sediments collected along a Chilean margin transect we chemically extracted reactive phases and separated the clay-sized sediment fraction. We compare the riverine and marine 10Be/9Be ratio of this fraction. Moreover, we compare the elemental and mineralogical composition and the Nd and Sr-isotopic composition of these samples. 10Be/9Be ratios increase four-fold from riverine to marine sediment. We attribute this increase to the incorporation of Be high in 10Be/9Be from dissolved biogenic opal, which also serves as a Si-source for the precipitation of marine authigenic clays. 10Be/9Be ratios thus sensitively track reverse-weathering reactions forming marine authigenic clays.
    Keywords: 10Be; authigenic clay; beryllium; Cosmogenic nuclide; denudation; reverse weathering
    Type: Dataset
    Format: application/zip, 4 datasets
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  • 10
    Publication Date: 2023-01-30
    Keywords: Age, relative; Deglaciation; Holocene; Indo-Pacific Warm Pool; LGM; Number; Thermocline; Δδ18O; Δδ18O, standard deviation
    Type: Dataset
    Format: text/tab-separated-values, 804 data points
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