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  • AGU (American Geophysical Union)  (17)
  • Forschungszentrum Jülich, Projektträger Biologie, Energie, Ökologie, Bereich Meeres- und Polarforschung  (5)
  • 11
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    Geochemie und magmatische Entwicklung der Übergangszone zwischen kontinentaler und ozeanischer Kruste am aktiven Spreizungszentrum des Woodlark-Beckens (SO203) (2011)
    Forschungszentrum Jülich, Projektträger Biologie, Energie, Ökologie, Bereich Meeres- und Polarforschung
    In:  [Talk] In: Statusseminar Meeresforschung mit FS Sonne 2011, 09.02.-10.02.2011, Hannover . Tagungsband / Meeeresforschung mit FS Sonne : Statusseminar 2011 ; pp. 124-127 .
    Details
    Publication Date: 2019-09-23
    Type: Conference or Workshop Item , NonPeerReviewed
    Format: text
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    OceanRep: Talk
  • 12
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    SO208 PLUMEFLUX: Erste Ergebnisse der Haupt- und Spurenelementanalytik an vulkanischen Gläsern von Seamounts und dem Cocos-Nazca-Spreizungszentrum im zentralen Ostpazifik (2011)
    Forschungszentrum Jülich, Projektträger Biologie, Energie, Ökologie, Bereich Meeres- und Polarforschung
    In:  [Poster] In: Statusseminar Meeresforschung mit FS Sonne 2011, 09.-10.02.2011, Hannover . Tagungsband / Meeresforschung mit FS Sonne : Statusseminar 2011 ; pp. 230-233 .
    Details
    Publication Date: 2019-09-23
    Type: Conference or Workshop Item , NonPeerReviewed
    Format: text
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    OceanRep: Poster
  • 13
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    Comment on “A snapshot of climate variability at Tahiti at 9.5 ka using a fossil coral from IODP Expedition 310” by Kristine L. DeLong, Terrence M. Quinn, Chuan-Chou Shen, and Ke Lin (2011)
    AGU (American Geophysical Union)
    In:  Geochemistry, Geophysics, Geosystems, 12 (3). Q03012.
    Details
    Publication Date: 2019-09-23
    Description: [1] The Integrated Ocean Drilling Program (IODP) Expedition 310 recovered drill cores from the drowned reefs around the island of Tahiti (17°40′S, 149°30′W), many of which contained samples of massive corals from the genus Porites. Herein we report on one well-preserved fossil coral sample: a 13.6 cm long Porites sp. dated by uranium series techniques at 9523 ± 33 years. Monthly δ18O and Sr/Ca determinations reveal nine clear and robust annual cycles. Coral δ18O and Sr/Ca determinations estimate a mean temperature of ∼24.3°C (∼3.2°C colder than modern) for Tahiti at 9.5 ka; however, this estimate is viewed with caution since potential sources of cold bias in coral geochemistry remain to be resolved. The interannual variability in coral δ18O is similar between the 9.5 ka coral record and a modern record from nearby Moorea. The seasonal cycle in coral Sr/Ca is approximately the same or greater in the 9.5 ka coral record than in modern coral records from Tahiti. Paired analysis of coral δ18O and Sr/Ca indicates cold/wet (warm/dry) interannual anomalies, opposite from those observed in the modern instrumental record.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2010GC003377
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 14
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    Pliocene Indonesian Throughflow and Leeuwin Current dynamics: Implications for Indian Ocean polar heat flux (2011)
    AGU (American Geophysical Union)
    In:  Paleoceanography, 26 (2). PA2217.
    Details
    Publication Date: 2019-09-23
    Description: To understand the gradual global cooling during the mid-Pliocene (3.5–2.5 Myr ago) one needs to consider the tectonical constriction of tropical seaways, which affected ocean circulation and the evolution of climate. Here we use paired measurements of δ18O and Mg/Ca ratios of planktonic foraminifera to reconstruct the Pliocene hydrography of the western tropical Indian Ocean (Site 709C) and changes in the Leeuwin Current in the eastern subtropical Indian Ocean (Site 763A) in response to Indonesian Gateway dynamics. Today, the Indonesian Throughflow (ITF) and, subsequently, the warm southward flowing Leeuwin Current off Western Australia are essential for the polar heat transport in the Indian Ocean. During 3.5–3 Ma, sea surface temperatures significantly dropped in the Leeuwin Current area, becoming since ~3.3 Ma 2°C–3°C cooler than the rather unchanged sea surface temperatures from the eastern and western tropical Indian Ocean. We refer this drop in sea surface temperatures to a weakened Leeuwin Current with severe climatic effects on Western Australia induced by a tectonically reduced surface ITF. We suggest that this reduced surface ITF led to a diminished poleward heat transport in the Indian Ocean resulting in a weakened Leeuwin Current and possibly to cooling of the Benguela upwelling system.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2010PA001949
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 15
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    Hydrological variability in Florida Straits during Marine Isotope Stage 5 cold events (2011)
    AGU (American Geophysical Union)
    In:  Paleoceanography, 26 (2). PA2214.
    Details
    Publication Date: 2017-05-10
    Description: Modeling and proxy studies indicate that a reduction of Atlantic Meridional Overturning Circulation (AMOC) strength profoundly impacts temperatures and salinities in the (sub)tropical Atlantic, especially on subsurface levels. While previous studies focused on prominent periods of AMOC reduction during the last deglaciation, we aim to test whether similar reconfigurations of the subtropical hydrography occurred during the moderate climatic alterations punctuating the last interglacial Marine Isotope Stage (MIS) 5. Here, we present temperature and salinity records from a Florida Straits core by combining d18O and Mg/Ca analyses on surface (Globigerinoides ruber, white) and deep‐dwelling (Globorotalia crassaformis) foraminifera covering MIS 5 in high resolution. The data reveal increasing salinities at intermediate depths during interglacial cooling episodes, decoupled from relatively stable surface conditions. This probably indicates the spatial expansion of saline subtropical gyre waters due to enhanced Ekman downwelling and might also point to a changed density structure and altered geostrophic balance in Florida Straits. Notably, these oceanographic alterations are not consistently occurring during periods of AMOC reduction. The data suggest that the expansion of gyre waters into Florida Straits was impeded by the increasing influence of Antarctic Intermediate Water (AAIW) from MIS 5.5 to ∼107 kyr BP. Afterward, increasingly positive benthic d13C values imply a recession of AAIW, allowing the temporary expansion of gyre waters into Florida Straits. We argue that the inferred transient subtropical salt accumulation and warm pool expansion might have played a pivotal role in reinvigorating meridional overturning and dampen the severity of interglacial cold phases.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2010PA002015
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 16
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    Surface ocean iron fertilization: the role of subduction zone and hotspot volcanic ash and fluxes into the Pacific Ocean (2011)
    AGU (American Geophysical Union)
    In:  Global Biogeochemical Cycles, 25 . GB4001.
    Details
    Publication Date: 2019-09-23
    Description: Surface ocean iron (Fe) fertilization can affect the marine primary productivity (MPP), thereby impacting on CO2 exchanges at the atmosphere-ocean interface and eventually on climate. Mineral (aeolian or desert) dust is known to be a major atmospheric source for the surface ocean biogeochemical iron cycle, but the significance of volcanic ash is poorly constrained. We present the results of geochemical experiments aimed at determining the rapid release of Fe upon contact of pristine volcanic ash with seawater, mimicking their dry deposition into the surface ocean. Our data show that volcanic ash from both subduction zone and hot spot volcanoes (n = 44 samples) rapidly mobilized significant amounts of soluble Fe into seawater (35–340 nmol/g ash), with a suggested global mean of 200 ± 50 nmol Fe/g ash. These values are comparable to the range for desert dust in experiments at seawater pH (10–125 nmol Fe/g dust) presented in the literature (Guieu et al., 1996; Spokes et al., 1996). Combining our new Fe release data with the calculated ash flux from a selected major eruption into the ocean as a case study demonstrates that single volcanic eruptions have the potential to significantly increase the surface ocean Fe concentration within an ash fallout area. We also constrain the long-term (millennial-scale) airborne volcanic ash and mineral dust Fe flux into the Pacific Ocean by merging the Fe release data with geological flux estimates. These show that the input of volcanic ash into the Pacific Ocean (128–221 × 1015 g/ka) is within the same order of magnitude as the mineral dust input (39–519 × 1015 g/ka) (Mahowald et al., 2005). From the similarity in both Fe release and particle flux follows that the flux of soluble Fe related to the dry deposition of volcanic ash (3–75 × 109 mol/ka) is comparable to that of mineral dust (1–65 × 109 mol/ka). Our study therefore suggests that airborne volcanic ash is an important but hitherto underestimated atmospheric source for the Pacific surface ocean biogeochemical iron cycle.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2009GB003761
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 17
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    Geochemistry of primitive glasses from the Volcanologists Massif (Far Western Aleutian Arc) obtained during SO201-KALMAR (2011)
    Forschungszentrum Jülich, Projektträger Biologie, Energie, Ökologie, Bereich Meeres- und Polarforschung
    In:  [Poster] In: Statusseminar Meeresforschung mit FS Sonne 2011, 09.-10.02.2011, Hannover . Tagungsband / Meeresforschung mit FS Sonne : Statusseminar 2011 ; p. 253 .
    Details
    Publication Date: 2012-07-06
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 18
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    Tracking interannual to multidecadal-scale climate variability in the Atlantic Warm Pool using central Caribbean coral data (2018)
    AGU (American Geophysical Union) | Wiley
    Details
    Publication Date: 2023-11-08
    Description: Atlantic Warm Pool (AWP) climate variability is subject to multiple influences of remote and local forcing. However, shortage of observational data before the mid‐20th century and of long‐term sea surface temperature (SST) and climate records has hampered the detection and investigation of decadal‐ and longer‐scale variability. We present new seasonally resolved 125‐year records of coral δ18O and Sr/Ca variations in the Central Caribbean Sea (Little Cayman, Cayman Islands; Diploria strigosa). Both geochemical proxies show decreasing long‐term trends, indicating long‐term warming. Sr/Ca indicates much stronger regional warming than large‐scale grid‐SST data, while δ18O tracks large‐scale SST changes in the AWP. Seawater δ18O variations are reconstructed, indicating a drying trend over the past century. High spatial correlation between coral δ18O and SST in the region of the Loop Current and Gulf Stream system suggests that Little Cayman is a sensitive location for detecting past large‐scale temperature variability beyond the central Caribbean region. More specifically, our δ18O data tracks changes in North Atlantic Oscillation (NAO) variability on decadal and multidecadal time scales providing insights into the temporal and spatial nonstationarity of the NAO. A combination of our δ18O record with two coral records from different Caribbean sites reveals high spatial correspondence between coral δ18O and SST variability in the North Atlantic subtropical gyre, where few instrumental measurements and proxies are available prior to the 20th century. Our results clearly demonstrate the potential of combining proxy data to provide information from sparsely sampled areas, helping to reduce uncertainty in model‐based projections.
    Type: Article , PeerReviewed
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 19
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    20th Century δ 18 O Seawater and Salinity Variations Reconstructed From Paired δ 18 O and Sr/Ca Measurements of a La Reunion Coral (2019)
    AGU (American Geophysical Union) | Wiley
    In:  Paleoceanography and Paleoclimatology, 34 . pp. 2183-2200.
    Details
    Publication Date: 2022-01-31
    Description: Sea surface salinity (SSS) is an important variable in the global ocean circulation. However, decadal to interdecadal changes in SSS are not well understood due to the lack of instrumental data. Here we reconstruct SSS from a paired, bimonthly resolved coral δ18O and Sr/Ca record from La Reunion Island that extends from 1913 to 1995. Coral Sr/Ca correlates with regional sea surface temperature (SST) back to 1966, when instrumental coverage is good, while coral δ18O does not. The slope of the monthly (annual mean) coral Sr/Ca-SST regression is −0.040 mmol/mol per 1 °C (−0.068 mmol/mol per 1 °C) consistent with published estimates of the Sr/Ca-SST relationship. Coral Sr/Ca suggest a warming of 0.39 °C since 1913. δ18O seawater is calculated by subtracting the temperature component from measured coral δ18O, using coral Sr/Ca as well as historical SST products. The derived δ18O seawater reconstructions are correlated (r 〉 0.6), and all show a significant shift in the midtwentieth century (−0.17‰ to −0.19‰), indicating a freshening of SSS by 0.7 psu. However, the timing of this shift depends on the temperature component and varies from 1947 (δ18O seawater calculated with historical SST) to the late 1950s (δ18O seawater calculated with coral Sr/Ca). Coral Sr/Ca shows warm temperature anomalies in the mid-1950s, while historical SST products show warm anomalies from 1940 to 1945 followed by cooling in the 1950s, a pattern typical for the World War II bias. This suggests that historical SST may bias reconstructions of δ18O seawater and SSS from corals.
    Type: Article , PeerReviewed
    Format: text
    Format: other
    Format: text
    DOI: 10.1029/2019PA003770
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 20
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    Papanin Ridge and Ojin Rise Seamounts (Northwest Pacific): Dual Hotspot Tracks Formed by the Shatsky Plume (2021)
    AGU (American Geophysical Union) | Wiley
    Details
    Publication Date: 2024-02-07
    Description: Although previous findings support an origin of the Shatsky Rise igneous plateau (Northwest Pacific) through interaction of a mantle plume with a mid-ocean ridge triple junction, the evidence for the involvement of a mantle plume is equivocal. The identification of an intraplate hotspot track emanating from the plateau could solve this controversy. Here we present major and trace element geochemical data from two different bathymetric features that emanate from the youngest end of Shatsky Rise: Papanin Ridge and the Ojin Rise Seamount province. Combining our results with plate tectonic reconstructions, we conclude that Papanin Ridge represents a hotspot track formed by plume-ridge interaction. Whereas the southwestern part was formed along the path of the retreating Pacific-Farallon-Izanagi triple junction, the northeastern part was built by preferential drainage into its Pacific-Farallon branch. In contrast, the Ojin Rise Seamounts formed as a true intraplate hotspot track of the Shatsky plume tail. Our wide-ranging study reveals systematic spatial geochemical variations, consistent with a lithospheric thickness control on magma composition derived from melting a heterogeneous plume source. The recognition of two hotspot tracks and in particular of the Ojin Rise Seamounts as an intraplate hotspot track that is directly linked to Shatsky plateau volcanism both in terms of geochemistry and plate tectonic reconstructions confirms the long-disputed involvement of a mantle plume for the formation of Shatsky Rise.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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