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  1. Article ; Online: Author Correction: Complex spatio-temporal structure of the Holocene thermal maximum.

    Cartapanis, Olivier / Jonkers, Lukas / Moffa-Sanchez, Paola / Jaccard, Samuel L / de Vernal, Anne

    Nature communications

    2022  Volume 13, Issue 1, Page(s) 6751

    Language English
    Publishing date 2022-11-08
    Publishing country England
    Document type Published Erratum
    ZDB-ID 2553671-0
    ISSN 2041-1723 ; 2041-1723
    ISSN (online) 2041-1723
    ISSN 2041-1723
    DOI 10.1038/s41467-022-34499-9
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Complex spatio-temporal structure of the Holocene Thermal Maximum.

    Cartapanis, Olivier / Jonkers, Lukas / Moffa-Sanchez, Paola / Jaccard, Samuel L / de Vernal, Anne

    Nature communications

    2022  Volume 13, Issue 1, Page(s) 5662

    Abstract: Inconsistencies between Holocene climate reconstructions and numerical model simulations question the robustness of climate models and proxy temperature records. Climate reconstructions suggest an early-middle Holocene Thermal Maximum (HTM) followed by ... ...

    Abstract Inconsistencies between Holocene climate reconstructions and numerical model simulations question the robustness of climate models and proxy temperature records. Climate reconstructions suggest an early-middle Holocene Thermal Maximum (HTM) followed by gradual cooling, whereas climate models indicate continuous warming. This discrepancy either implies seasonal biases in proxy-based climate reconstructions, or that the climate model sensitivity to forcings and feedbacks needs to be reevaluated. Here, we analyze a global database of Holocene paleotemperature records to investigate the spatiotemporal structure of the HTM. Continental proxy records at mid and high latitudes of the Northern Hemisphere portray a "classic" HTM (8-4 ka). In contrast, marine proxy records from the same latitudes reveal an earlier HTM (11-7ka), while a clear temperature anomaly is missing in the tropics. The results indicate a heterogeneous response to climate forcing and highlight the lack of globally synchronous HTM.
    MeSH term(s) Climate ; Climate Change ; Cold Temperature ; Temperature
    Language English
    Publishing date 2022-10-03
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2553671-0
    ISSN 2041-1723 ; 2041-1723
    ISSN (online) 2041-1723
    ISSN 2041-1723
    DOI 10.1038/s41467-022-33362-1
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Pre-aged terrigenous organic carbon biases ocean ventilation-age reconstructions in the North Atlantic.

    Liu, Jingyu / Wang, Yipeng / Jaccard, Samuel L / Wang, Nan / Gong, Xun / Fang, Nianqiao / Bao, Rui

    Nature communications

    2023  Volume 14, Issue 1, Page(s) 3788

    Abstract: Changes in ocean ventilation have been pivotal in regulating carbon sequestration and release on centennial to millennial timescales. However, paleoceanographic reconstructions documenting changes in deep-ocean ventilation ... ...

    Abstract Changes in ocean ventilation have been pivotal in regulating carbon sequestration and release on centennial to millennial timescales. However, paleoceanographic reconstructions documenting changes in deep-ocean ventilation using
    MeSH term(s) Seawater ; Carbon ; Ice Cover ; Respiration ; Bias ; Oceans and Seas ; Atlantic Ocean
    Chemical Substances Carbon (7440-44-0)
    Language English
    Publishing date 2023-06-24
    Publishing country England
    Document type Journal Article
    ZDB-ID 2553671-0
    ISSN 2041-1723 ; 2041-1723
    ISSN (online) 2041-1723
    ISSN 2041-1723
    DOI 10.1038/s41467-023-39490-6
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Book ; Online: Modeling the marine chromium cycle

    Pöppelmeier, Frerk / Janssen, David J. / Jaccard, Samuel L. / Stocker, Thomas F.

    eISSN: 1726-4189

    new constraints on global-scale processes

    2021  

    Abstract: Chromium (Cr) and its isotopes hold great promise as a tracer of past oxygenation and marine biological activity due to the contrasted chemical properties of its two main oxidation states, Cr(III) and Cr(VI), and the associated isotope fractionation ... ...

    Abstract Chromium (Cr) and its isotopes hold great promise as a tracer of past oxygenation and marine biological activity due to the contrasted chemical properties of its two main oxidation states, Cr(III) and Cr(VI), and the associated isotope fractionation during redox transformations. However, to date the marine Cr cycle remains poorly constrained due to insufficient knowledge about sources and sinks and the influence of biological activity on redox reactions. We therefore implemented the two oxidation states of Cr in the Bern3D Earth system model of intermediate complexity in order to gain an improved understanding on the mechanisms that modulate the spatial distribution of Cr in the ocean. Due to the computational efficiency of the Bern3D model we are able to explore and constrain the range of a wide array of parameters. Our model simulates vertical, meridional, and inter-basin Cr concentration gradients in good agreement with observations. We find a mean ocean residence time of Cr between 5 and 8 kyr and a benthic flux, emanating from sediment surfaces, of 0.1–0.2 nmol cm −2 yr −1 , both in the range of previous estimates. We further explore the origin of regional model–data mismatches through a number of sensitivity experiments. These indicate that the benthic Cr flux may be substantially lower in the Arctic than elsewhere. In addition, we find that a refined representation of oxygen minimum zones and their potential to reduce Cr yield Cr(III) concentrations and Cr removal rates in these regions in much improved agreement with observational data. Yet, further research is required to better understand the processes that govern these critical regions for Cr cycling.
    Subject code 333
    Language English
    Publishing date 2021-10-07
    Publishing country de
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  5. Article: Biological Control of Chromium Redox and Stable Isotope Composition in the Surface Ocean.

    Janssen, David J / Rickli, Jörg / Quay, Paul D / White, Angelicque E / Nasemann, Philipp / Jaccard, Samuel L

    Global biogeochemical cycles

    2020  Volume 34, Issue 1, Page(s) e2019GB006397

    Abstract: While chromium stable isotopes ( ... ...

    Abstract While chromium stable isotopes (δ
    Language English
    Publishing date 2020-01-16
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2021601-4
    ISSN 1944-9224 ; 0886-6236
    ISSN (online) 1944-9224
    ISSN 0886-6236
    DOI 10.1029/2019GB006397
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Deglacial patterns of South Pacific overturning inferred from

    Ronge, Thomas A / Lippold, Jörg / Geibert, Walter / Jaccard, Samuel L / Mieruch-Schnülle, Sebastian / Süfke, Finn / Tiedemann, Ralf

    Scientific reports

    2021  Volume 11, Issue 1, Page(s) 20473

    Abstract: The millennial-scale variability of the Atlantic Meridional Overturning Circulation (AMOC) is well documented for the last glacial termination and beyond. Despite its importance for the climate system, the evolution of the South Pacific overturning ... ...

    Abstract The millennial-scale variability of the Atlantic Meridional Overturning Circulation (AMOC) is well documented for the last glacial termination and beyond. Despite its importance for the climate system, the evolution of the South Pacific overturning circulation (SPOC) is by far less well understood. A recently published study highlights the potential applicability of the
    Language English
    Publishing date 2021-10-14
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2615211-3
    ISSN 2045-2322 ; 2045-2322
    ISSN (online) 2045-2322
    ISSN 2045-2322
    DOI 10.1038/s41598-021-00111-1
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Book ; Online: Carbon burial in deep-sea sediment and implications for oceanic inventories of carbon and alkalinity over the last glacial cycle

    Cartapanis, Olivier / Galbraith, Eric D. / Bianchi, Daniele / Jaccard, Samuel L.

    eISSN: 1814-9332

    2019  

    Abstract: Although it has long been assumed that the glacial–interglacial cycles of atmospheric CO 2 occurred due to increased storage of CO 2 in the ocean, with no change in the size of the “active” carbon inventory, there are signs that the geological CO 2 ... ...

    Abstract Although it has long been assumed that the glacial–interglacial cycles of atmospheric CO 2 occurred due to increased storage of CO 2 in the ocean, with no change in the size of the “active” carbon inventory, there are signs that the geological CO 2 supply rate to the active pool varied significantly. The resulting changes of the carbon inventory cannot be assessed without constraining the rate of carbon removal from the system, which largely occurs in marine sediments. The oceanic supply of alkalinity is also removed by the burial of calcium carbonate in marine sediments, which plays a major role in air–sea partitioning of the active carbon inventory. Here, we present the first global reconstruction of carbon and alkalinity burial in deep-sea sediments over the last glacial cycle. Although subject to large uncertainties, the reconstruction provides a first-order constraint on the effects of changes in deep-sea burial fluxes on global carbon and alkalinity inventories over the last glacial cycle. The results suggest that reduced burial of carbonate in the Atlantic Ocean was not entirely compensated by the increased burial in the Pacific basin during the last glacial period, which would have caused a gradual buildup of alkalinity in the ocean. We also consider the magnitude of possible changes in the larger but poorly constrained rates of burial on continental shelves, and show that these could have been significantly larger than the deep-sea burial changes. The burial-driven inventory variations are sufficiently large to have significantly altered the δ 13 C of the ocean–atmosphere carbon and changed the average dissolved inorganic carbon (DIC) and alkalinity concentrations of the ocean by more than 100 µ M, confirming that carbon burial fluxes were a dynamic, interactive component of the glacial cycles that significantly modified the size of the active carbon pool. Our results also suggest that geological sources and sinks were significantly unbalanced during the late Holocene, leading to a slow net removal flux on the order of 0.1 PgC yr −1 prior to the rapid input of carbon during the industrial period.
    Subject code 333
    Language English
    Publishing date 2019-02-19
    Publishing country de
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  8. Article ; Online: Chromium reduction and associated stable isotope fractionation restricted to anoxic shelf waters in the Peruvian Oxygen Minimum Zone

    Nasemann, Philipp / Janssen, David J. / Rickli, Jörg / Grasse, Patricia / Frank, Martin / Jaccard, Samuel L.

    2020  

    Abstract: The marine chromium (Cr) cycle is still insufficiently understood, in particular the mechanisms modulating the spatial distribution of dissolved stable Cr isotopes in seawater. Redox transformations between its main oxidation states, Cr(VI) and Cr(III), ... ...

    Abstract The marine chromium (Cr) cycle is still insufficiently understood, in particular the mechanisms modulating the spatial distribution of dissolved stable Cr isotopes in seawater. Redox transformations between its main oxidation states, Cr(VI) and Cr(III), have been held accountable for the observed tight inverse logarithmic relationship between the dissolved Cr concentration [Cr] and its isotopic composition (δ53Cr), whereby isotopically light Cr(III) is removed in surface waters and oxygen minimum zones (OMZs), and subsequently released to deeper waters from remineralized particles or sediments. Seawater [Cr] and δ53Cr were investigated in a series of depth profiles across the Peruvian margin OMZ, covering a wide spectrum of dissolved oxygen concentrations ranging from 2 to 242 µmol/kg. We found [Cr] ranging from 1.5 to 5.5 nmol/kg, associated with δ53Cr variations between +1.59 and +0.72 ‰, but no systematic relationship to dissolved oxygen concentrations. However, distinctly different seawater profiles were observed above the suboxic/anoxic shelf compared to those located further offshore, with substantial Cr removal restricted to suboxic or anoxic environments on the shelf. This suggests that suboxic conditions ([O2] < 5 µmol/kg) alone are not sufficient to account for substantial Cr removal. Given that environmental conditions under which Cr can be reduced remain restricted spatially, the role of this sink in the marine Cr cycle may therefore be small. Additionally, some observations corroborate the assumption that Cr reduction is not necessarily accompanied by immediate adsorption of the formed Cr(III) onto particles, leading to its removal from the dissolved phase. Instead, partial removal of Cr(III) via particles, leaving a residual dissolved Cr(III) pool, may be more widespread in suboxic waters.
    Subject code 551
    Language English
    Publishing date 2020-09-15
    Publisher Elsevier
    Publishing country de
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  9. Article ; Online: Enhanced ocean-atmosphere carbon partitioning via the carbonate counter pump during the last deglacial.

    Duchamp-Alphonse, Stéphanie / Siani, Giuseppe / Michel, Elisabeth / Beaufort, Luc / Gally, Yves / Jaccard, Samuel L

    Nature communications

    2018  Volume 9, Issue 1, Page(s) 2396

    Abstract: Several synergistic mechanisms were likely involved in the last deglacial atmospheric ... ...

    Abstract Several synergistic mechanisms were likely involved in the last deglacial atmospheric pCO
    Language English
    Publishing date 2018-06-19
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2553671-0
    ISSN 2041-1723 ; 2041-1723
    ISSN (online) 2041-1723
    ISSN 2041-1723
    DOI 10.1038/s41467-018-04625-7
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  10. Article ; Online: Global pulses of organic carbon burial in deep-sea sediments during glacial maxima.

    Cartapanis, Olivier / Bianchi, Daniele / Jaccard, Samuel L / Galbraith, Eric D

    Nature communications

    2016  Volume 7, Page(s) 10796

    Abstract: The burial of organic carbon in marine sediments removes carbon dioxide from the ocean-atmosphere pool, provides energy to the deep biosphere, and on geological timescales drives the oxygenation of the atmosphere. Here we quantify natural variations in ... ...

    Abstract The burial of organic carbon in marine sediments removes carbon dioxide from the ocean-atmosphere pool, provides energy to the deep biosphere, and on geological timescales drives the oxygenation of the atmosphere. Here we quantify natural variations in the burial of organic carbon in deep-sea sediments over the last glacial cycle. Using a new data compilation of hundreds of sediment cores, we show that the accumulation rate of organic carbon in the deep sea was consistently higher (50%) during glacial maxima than during interglacials. The spatial pattern and temporal progression of the changes suggest that enhanced nutrient supply to parts of the surface ocean contributed to the glacial burial pulses, with likely additional contributions from more efficient transfer of organic matter to the deep sea and better preservation of organic matter due to reduced oxygen exposure. These results demonstrate a pronounced climate sensitivity for this global carbon cycle sink.
    Language English
    Publishing date 2016-02-29
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ISSN 2041-1723
    ISSN (online) 2041-1723
    DOI 10.1038/ncomms10796
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