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  • 1
    Electronic Resource
    Electronic Resource
    Eccentricity forcing of Pliocene–Early Pleistocene climate revealed in a marine oxygen-isotope record (1997)
    [s.l.] : Nature Publishing Group
    Nature 385 (1997), S. 801-804 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Figure 1 Benthic (Cibicidoides wuellerstorfi) 6180 record from Ocean Drilling Program Site 659 (18°05' N, 21°02' W, 3,070m water depth). Age control is based on oxygen-isotope chronostratigraphy (0-2.85 Myr) and tuning the lithogenic component to 65° N July insolation (2.85-5.2 Myr), as ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/385801a0
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular record of secular sea surface temperature changes on 100-year timescales for glacial terminations I, II and IV (1992)
    [s.l.] : Nature Publishing Group
    Nature 356 (1992), S. 423-426 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] OOP site 658 was cored5 below the high-productivity zone of the main upwelling cell off northwest Africa, on the continental slope 160 km west of Cape Blanc11 (20° 45' N, 18° 35' W; 2,263 m water depth). The coastal upwelling off Cape Blanc is driven by the northeast trade winds on a ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/356423a0
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  • 3
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    Chlorin accumulation rate as a proxy for Quaternary marine primary productivity (1996)
    Nature Publishing Group
    In:  Nature, 383 (6595). pp. 63-65.
    Details
    Publication Date: 2017-02-27
    Description: A knowledge of past changes in the biological productivity of the oceans is important for understanding the interactions between carbon cycling and climate. Phytoplankton productivity in today's oceans can be estimated from the concentrations of chlorophyll in sea water1, but chlorophyll is not preserved in the sediments. Existing proxies for past algal productivity do not represent total productivity; for example, biogenic opal2 reflects the contribution of only part of the phytoplankton community, and the organic carbon record can be subject to contamination from terrestrial inputs2,3. Although chlorins, the pigment-transformation products of chlorophyll, are widespread in Quaternary marine sediments, their potential as proxy measures of past variations in primary productivity has not been convincingly demonstrated. Here we report a high-resolution molecular stratigraphic record of chlorin concentrations over the past 350,000 years in a sediment core from the subtropical Atlantic continental margin. Maxima in the chlorin accumulation rate coincide with significant peaks in the accumulation rates of biogenic opal (at the end of glacial terminations) and organic carbon (between terminations). These results suggest that chlorins, unlike other proxies, can serve as a measure of total primary productivity variations.
    Type: Article , PeerReviewed
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  • 4
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    North Pacific seasonality and the glaciation of North America 2.7 million years ago (2005)
    Nature Publishing Group
    In:  Nature, 433 . pp. 821-825.
    Details
    Publication Date: 2019-09-23
    Description: In the context of gradual Cenozoic cooling, the timing of the onset of significant Northern Hemisphere glaciation 2.7 million years ago is consistent with Milankovitch's orbital theory, which posited that ice sheets grow when polar summertime insolation and temperature are low. However, the role of moisture supply in the initiation of large Northern Hemisphere ice sheets has remained unclear. The subarctic Pacific Ocean represents a significant source of water vapour to boreal North America, but it has been largely overlooked in efforts to explain Northern Hemisphere glaciation. Here we present alkenone unsaturation ratios and diatom oxygen isotope ratios from a sediment core in the western subarctic Pacific Ocean, indicating that 2.7 million years ago late-summer sea surface temperatures in this ocean region rose in response to an increase in stratification. At the same time, winter sea surface temperatures cooled, winter floating ice became more abundant and global climate descended into glacial conditions. We suggest that the observed summer warming extended into the autumn, providing water vapour to northern North America, where it precipitated and accumulated as snow, and thus allowed the initiation of Northern Hemisphere glaciation.
    Type: Article , PeerReviewed
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    Format: text
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  • 5
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    Mid-Pliocene climate change amplified by a switch in Indonesian subsurface throughflow (2009)
    Nature Publishing Group
    In:  Nature Geoscience, 2 . pp. 434-438.
    Details
    Publication Date: 2019-09-23
    Description: The tectonically driven closure of tropical seaways during the Pliocene epoch (approx5–2 million years (Myr) ago) altered ocean circulation and affected the evolution of climate. Plate tectonic reconstructions show that the main reorganization of one such seaway, the Indonesian Gateway, occurred between 4 and 3 Myr ago. Model simulations have suggested that this would have triggered a switch in the source of waters feeding the Indonesian throughflow into the Indian Ocean, from the warm salty waters of the South Pacific Ocean to the cool and relatively fresh waters of the North Pacific Ocean. Here we use paired measurements of the delta18O and Mg/Ca ratios of planktonic foraminifera to reconstruct the thermal structure of the eastern tropical Indian Ocean from 5.5 to 2 Myr ago. We find that sea surface conditions remained relatively stable throughout the interval, whereas subsurface waters freshened and cooled by about 4 °C between 3.5 and 2.95 Myr ago. We suggest that the restriction of the Indonesian Gateway led to the cooling and shoaling of the thermocline in the tropical Indian Ocean. We conclude that this tectonic reorganization contributed to the global shoaling of the thermocline recorded during the Pliocene epoch, possibly contributing to the development of the equatorial eastern Pacific cold tongue.
    Type: Article , PeerReviewed
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  • 6
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    Persistent summer expansion of the Atlantic Warm Pool during glacial abrupt cold events (2008)
    Nature Publishing Group
    Details
    Publication Date: 2023-01-31
    Description: Palaeoclimate records and numerical model simulations indicate that changes in tropical and subtropical sea surface temperatures and in the annual average position of the intertropical convergence zone are linked to high-latitude climate changes on millennial to glacial–interglacial timescales. It has recently been suggested that cooling in the high latitudes associated with abrupt climate-change events is evident primarily during the northern hemisphere winter, implying increased seasonality at these times8. However, it is unclear whether such a seasonal bias also exists for the low latitudes. Here we analyse the Mg/Ca ratios of surface-dwelling foraminifera to reconstruct sea surface temperatures in the northeastern Gulf of Mexico for the past 300,000 years. We suggest that sea surface temperatures are controlled by the migration of the northern boundary of the Atlantic Warm Pool, and hence the position of the intertropical convergence zone during boreal summer, and are relatively insensitive to winter conditions. Our results suggest that summer Atlantic Warm Pool expansion is primarily affected by glacial–interglacial variability and low-latitude summer insolation. Because a clear signature of rapid climate-change events, such as the Younger Dryas cold event, is lacking in our record, we conclude that high-latitude events seem to influence only the winter Caribbean climate conditions, consistent with the hypothesis of extreme northern-hemisphere seasonality during abrupt cooling events.
    Type: Article , PeerReviewed
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