ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    facet.materialart.
    Unknown
    PANGAEA
    In:  Supplement to: Bartoli, Gretta; Hönisch, Bärbel; Zeebe, Richard E (2011): Atmospheric CO2 decline during the Pliocene intensification of Northern Hemisphere glaciations. Paleoceanography, 26(4), PA4213, https://doi.org/10.1029/2010PA002055
    Publication Date: 2019-01-26
    Description: everal hypotheses have been put forward to explain the onset of intensive glaciations on Greenland, Scandinavia, and North America during the Pliocene epoch between 3.6 and 2.7 million years ago (Ma). A decrease in atmospheric CO2 may have played a role during the onset of glaciations, but other tectonic and oceanic events occurring at the same time may have played a part as well. Here we present detailed atmospheric CO2 estimates from boron isotopes in planktic foraminifer shells spanning 4.6-2.0 Ma. Maximal Pliocene atmospheric CO2 estimates gradually declined from values around 410 µatm to early Pleistocene values of 300 matm at 2.0 Ma. After the onset of large-scale ice sheets in the Northern Hemisphere, maximal pCO2 estimates were still at 2.5 Ma +90 µatm higher than values characteristic of the early Pleistocene interglacials. By contrast, Pliocene minimal atmospheric CO2 gradually decreased from 310 to 245 µatm at 3.2 Ma, coinciding with the start of transient glaciations on Greenland. Values characteristic of early Pleistocene glacial atmospheric CO2 of 200 matm were abruptly reached after 2.7 Ma during the late Pliocene transition. This trend is consistent with the suggestion that ocean stratification and iron fertilization increased after 2.7 Ma in the North Pacific and Southern Ocean and may have led to increased glacial CO2 storage in the oceanic abyss after 2.7 Ma onward.
    Type: Dataset
    Format: text/tab-separated-values, 659 data points
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    facet.materialart.
    Unknown
    PANGAEA
    In:  Supplement to: Hönisch, Bärbel; Hemming, N Gary (2004): Ground-truthing the boron isotope-paleo-pH proxy in planktonic foraminifera shells: Partial dissolution and shell size effects. Paleoceanography, 19(4), PA4010, https://doi.org/10.1029/2004PA001026
    Publication Date: 2019-01-26
    Description: Sediment samples from the Ontong-Java Plateau in the Pacific and the 90° east ridge in the Indian Ocean were used to investigate whether shell size and early diagenesis affect d11B of the symbiont-bearing planktonic foraminifer Globigerinoides sacculifer. In pristine shells from both study locations we found a systematic increase of d11B and Mg/Ca with shell size. Shells in the sieve size class 515–865 µm revealed d11B values +2.1 to +2.3 per mil higher than shells in the 250–380 µm class. This pattern is most likely due to differences in symbiont photosynthetic activity and its integrated effect on the pH of the foraminiferal microenvironment. We therefore suggest smaller individuals must live at approximately 50–100 m water depth where ambient light levels are lower. Using the empirical calibration curve for d11B in G. sacculifer, only shells larger than 425 µm reflect surface seawater pH. Partial dissolution of shells derived from deeper sediment cores was determined by shell weight analyses and investigation of the shell surface microstructure by scanning electron microscopy. The d11B in partially dissolved shells is up to 2 per mil lower relative to pristine shells of the same size class. In agreement with a relatively higher weight loss in smaller shells, samples from the Ontong-Java Plateau show a more pronounced dissolution effect than larger shells. On the basis of the primary size effect and potential postdepositional dissolution effects, we recommend the use of shells that are visually pristine and, in the case of G. sacculifer, larger than 500 μm for paleoreconstructions.
    Type: Dataset
    Format: text/tab-separated-values, 169 data points
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    facet.materialart.
    Unknown
    PANGAEA
    In:  Supplement to: Hönisch, Bärbel; Hemming, N Gary (2005): Surface ocean pH response to variations in pCO2 through two full glacial cycles. Earth and Planetary Science Letters, 236(1-2), 305-314, https://doi.org/10.1016/j.epsl.2005.04.027
    Publication Date: 2019-01-26
    Description: Knowledge of past atmospheric pCO2 is important for evaluating the role of greenhouse gases in climate forcing. Ice core records show the tight correlation between climate change and pCO2, but records are limited to the past ~900 kyr. We present surface ocean pH and pCO2 data, reconstructed from boron isotopes in planktonic foraminifera over two full glacial cycles (0-140 and 300-420 kyr). The data co-vary strongly with the Vostok pCO2-record and demonstrate that the coupling between surface ocean chemistry and the atmosphere is recorded in marine archives, allowing for quantitative estimation of atmospheric pCO2 beyond the reach of ice cores.
    Type: Dataset
    Format: text/tab-separated-values, 308 data points
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    facet.materialart.
    Unknown
    PANGAEA
    In:  Supplement to: Hönisch, Bärbel; Bickert, Torsten; Hemming, N Gary (2008): Modern and Pleistocene boron isotope composition of the benthic foraminifer Cibicidoides wuellerstorfi. Earth and Planetary Science Letters, 272(1-2), 309-318, https://doi.org/10.1016/j.epsl.2008.04.047
    Publication Date: 2019-01-26
    Description: Here we present the first species-specific study of boron isotopes in the epibenthic foraminifer species Cibicidoides wuellerstorfi. Coretop samples from a water depth profile from 1000 to 4500 m on the northern flank of the Walvis Ridge are 4.4 per mil lower than the values expected, based on calculations of the delta 11B(borate) of ambient seawater. Similar values for this foraminifer species are presented from ODP site 668B at the Sierra Leone Rise, in the equatorial Atlantic. The consistency between data of the same species suggests the offsets are primary, rather than diagenetic. Glacial C. wuellerstorfi from ODP 668B and Walvis Ridge have boron isotope compositions only slightly different to interglacial samples, that is no larger than +0.10 pH units, or +23 µmol/kg in [CO3[2-]] above the reconstructed glacial lysocline, and -0.07 pH units, or -14 µmol/kg in [CO3[2-]] below. We use these results to suggest that glacial deep water pH in the Atlantic was similar to interglacial pH. The new data resolve the inconsistency between the previously reported high bottom water pH and the lack of significant carbonate preservation of the glacial deep ocean.
    Type: Dataset
    Format: text/tab-separated-values, 26 data points
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Publication Date: 2017-06-07
    Description: In order to address the correct reporting and therefore comparison of isotopic measurements across different instrument types and instrumental techniques a prepared set of synthetic standards was sent to 28 laboratories for boron (B) isotopic analyses. Standards were prepared from enriched and purified isotopic salts to avoid any sample preparation fractionation. The range in uncertainties of the analyses between different instrumental analytical techniques is as large as the differences within an instrumental analytical technique obscuring any systematic offset. We conclude that uncertainties in the measurement of delta(11)B values were often underestimated and a procedure is suggested to allow a better comparison of the different techniques. Two new standards (JABA and JABB) have been quantified and these are available to all laboratories for testing their analyses. The delta(11)B values of these new standards are 10.0 parts per thousand and -23.7 parts per thousand. The results from this exercise impact on the way all isotope measurements are performed and reported. Guidelines are defined to aid the comparison of measurements between different laboratories.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Publication Date: 2019-02-22
    Type: Dataset
    Format: text/tab-separated-values, 864 data points
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Publication Date: 2019-02-22
    Type: Dataset
    Format: text/tab-separated-values, 17688 data points
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    Publication Date: 2019-02-22
    Type: Dataset
    Format: text/tab-separated-values, 26526 data points
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Publication Date: 2019-02-22
    Type: Dataset
    Format: text/tab-separated-values, 3984 data points
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    facet.materialart.
    Unknown
    PANGAEA
    In:  Supplement to: Hönisch, Bärbel; Hemming, N Gary; Archer, David E; Siddall, Mark; McManus, Jerry F (2009): Atmospheric Carbon Dioxide Concentration Across the Mid-Pleistocene Transition. Science, 324(5934), 1551-1554, https://doi.org/10.1126/science.1171477
    Publication Date: 2019-01-26
    Description: The dominant period of Pleistocene glacial cycles changed during the mid-Pleistocene from 40,000 years to 100,000 years, for as yet unknown reasons. Here we present a 2.1-million-year record of sea surface partial pressure of CO2 (PCO2), based on boron isotopes in planktic foraminifer shells, which suggests that the atmospheric partial pressure of CO2 (pCO2) was relatively stable before the mid-Pleistocene climate transition. Glacial PCO2 was ~31 microatmospheres higher before the transition (more than 1 million years ago), but interglacial PCO2 was similar to that of late Pleistocene interglacial cycles (〈450,000 years ago). These estimates are consistent with a close linkage between atmospheric CO2 concentration and global climate, but the lack of a gradual decrease in interglacial PCO2 does not support the suggestion that a long-term drawdown of atmospheric CO2 was the main cause of the climate transition.
    Type: Dataset
    Format: text/tab-separated-values, 978 data points
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...