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  • Elsevier  (2)
  • 1
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    Low-latitude expressions of high-latitude forcing during Heinrich Stadial 1 and the Younger Dryas in northern South America (2018)
    Elsevier
    In:  Global and Planetary Change, 160 . pp. 1-9.
    Details
    Publication Date: 2021-02-08
    Description: Changes in Atlantic Meridional Overturning Circulation (AMOC) strength exert a major influence on global atmospheric circulation patterns. However, the pacing and mechanisms of low-latitude responses to high-latitude forcing are insufficiently constrained so far. To elucidate the interaction of atmospheric and oceanic forcing in tropical South America during periods of major AMOC reductions (Heinrich Stadial 1 and the Younger Dryas) we generated a high-resolution foraminiferal multi-proxy record from off the Orinoco River based on Ba/Ca and Mg/Ca ratios, as well as stable isotope measurements. The data clearly indicate a three-phased structure of HS1 based on the reconfiguration of ocean currents in the tropical Atlantic Ocean. The initial phase (HS1a) is characterized by a diminished North Brazil Current, a southward displacement of the ITCZ, and moist conditions dominating northeastern Brazil. During subsequent HS1b, the NBC was even more diminished or yet reversed and the ITCZ shifted to its southernmost position. Hence, dryer conditions prevailed in northern South America, while eastern Brazil experienced maximally wet conditions. During the final stage, HS1c, conditions are similar to HS1a. The YD represents a smaller amplitude version of HS1 with a southward-shifted ITCZ. Our findings imply that the low-latitude continental climate response to high-latitude forcing is mediated by reconfigurations of surface ocean currents in low latitudes. Our new records demonstrate the extreme sensitivity of the terrestrial realm in tropical South America to abrupt perturbations in oceanic circulation during periods of unstable climate conditions.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    Format: other
    DOI: 10.1016/j.gloplacha.2017.11.008
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Reconstruction of intermediate water circulation in the tropical North Atlantic during the past 22,000 years (2014)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 140 . pp. 455-467.
    Details
    Publication Date: 2018-09-11
    Description: Decades of paleoceanographic studies have reconstructed a well-resolved water mass structure for the deep Atlantic Ocean during the Last Glacial Maximum (LGM). However, the variability of intermediate water circulation in the tropics over the LGM and deglacial abrupt climate events is still largely debated. This study aims to reconstruct intermediate northern- and southern-sourced water circulation in the tropical North Atlantic during the past 22 kyr and attempts to confine the boundary between Antarctic Intermediate Water (AAIW) and northern-sourced intermediate water (i.e., upper North Atlantic Deep Water (NADW) or Glacial North Atlantic Intermediate Water) in the past. High-resolution Nd isotopic compositions of fish debris and acid-reductive leachate of bulk sediment in core VM12-107 (1079 m depth) from the Southern Caribbean are not in agreement. We suggest that the leachate method does not reliably extract the Nd isotopic compositions of seawater at this location, and that it needs to be tested in more detail in various oceanic settings. The fish debris εNd values display a general decrease from the early deglaciation to the end of the Younger Dryas, followed by a greater drop toward less radiogenic values into the early Holocene. We propose a potentially more radiogenic glacial northern endmember water mass and interpret this pattern as recording a recovery of the upper NADW during the last deglaciation. Comparing our new fish debris Nd isotope data to authigenic Nd isotope studies in the Florida Straits (546 and 751 m depth), we propose that both glacial and deglacial AAIW do not penetrate beyond the lower depth limit of modern AAIW in the tropical Atlantic.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1016/j.gca.2014.05.041
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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