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  • 1
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    Antarctic icebergs reorganize ocean circulation during Pleistocene glacials (2021)
    Nature Publishing Group
    In:  EPIC3Nature, Nature Publishing Group, 589(7841), pp. 236-241, ISSN: 0028-0836
    Details
    Publication Date: 2021-02-03
    Description: The dominant feature of large-scale mass transfer in the modern ocean is the Atlantic meridional overturning circulation (AMOC). The geometry and vigour of this circulation influences global climate on various timescales. Palaeoceanographic evidence suggests that during glacial periods of the past 1.5 million years the AMOC had markedly different features from today; in the Atlantic basin, deep waters of Southern Ocean origin increased in volume while above them the core of the North Atlantic Deep Water (NADW) shoaled. An absence of evidence on the origin of this phenomenon means that the sequence of events leading to global glacial conditions remains unclear. Here we present multi-proxy evidence showing that northward shifts in Antarctic iceberg melt in the Indian–Atlantic Southern Ocean (0–50°E) systematically preceded deep-water mass reorganizations by one to two thousand years during Pleistocene-era glaciations. With the aid of iceberg-trajectory model experiments, we demonstrate that such a shift in iceberg trajectories during glacial periods can result in a considerable redistribution of freshwater in the Southern Ocean. We suggest that this, in concert with increased sea-ice cover, enabled positive buoyancy anomalies to ‘escape’ into the upper limb of the AMOC, providing a teleconnection between surface Southern Ocean conditions and the formation of NADW. The magnitude and pacing of this mechanism evolved substantially across the mid-Pleistocene transition, and the coeval increase in magnitude of the ‘southern escape’ and deep circulation perturbations implicate this mechanism as a key feedback in the transition to the ‘100-kyr world’, in which glacial–interglacial cycles occur at roughly 100,000-year periods.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 2
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    Contourites at the eastern Agulhas Ridge and Cape Rise seamount shaped by Southern Ocean derived water masses (2014)
    Vlaams Instituut voor de Zee (VLIZ)
    In:  EPIC3Book of Abstracts. 2nd Deep-Water Circulation Congress: The Contourite Log-book, (VLIZ Special Publication ; 69), Oostende, Belgium, Vlaams Instituut voor de Zee (VLIZ), 152 p., pp. 77-78, ISBN: 1377-0950
    Details
    Publication Date: 2014-09-24
    Description: Constituting a topographic barrier the Agulhas Ridge has a strong influence on the exchange of water masses between high and lower latitudes in the South Atlantic. While Antarctic Bottomwater (AABW) and Circumpolar Deepwater (CDW) originating in the Southern Ocean provide the inflow of cold water masses in larger water depths, the Agulhas leakage is the main source of warm and salty waters carried towards the Subpolar North Atlantic. In order to track past changes in this circulation pattern 5400 km of high-resolution multichannel seismic reflection data were acquired during RV Maria S. Merian cruise MSM 19/2 in the Agulhas Ridge area. Here we present first results from the eastern plateau of the ridge and the area between the plateau and the Cape Rise Seamount. Via crosscorrelation with ODP Leg 177 drillsites, prominent reflectors marking the early Oligocene, the middle Miocene and the base of the Pleistocene were identified. Sediment drifts deposited between these erosional surfaces indicate steady contour current acitivity at various depth levels. Extensive current derived deposits in this area and a mounded drift northwest of the Cape Rise Seamounts formed by clockwise circulating bottom water appear to have been built contemporaneously by AABW flow after the early Oligocene.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Inbook , peerRev
    Format: application/pdf
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