Hydrographic shifts south of Australia over the last deglaciation and possible interhemispheric linkages

Type Article
Date 2021-07
Language English
Author(s) Moros MatthiasORCID1, de Deckker PatrickORCID2, Perner KerstinORCID1, Ninnemann Ulysses S.ORCID3, Wacker LukasORCID4, Telford RichardORCID5, Jansen EysteinORCID3, Blanz ThomasORCID6, Schneider RalphORCID6
Affiliation(s) 1 : Leibniz Institute for Baltic Sea Research Warnemünde, Rostock, Germany
2 : Research School of Earth Sciences, The Australian National University, Canberra, Australia
3 : Department of Earth Sciences, University of Bergen and Bjerknes Centre for Climate Research, Bergen, Norway
4 : Laboratory of Ion Beam Physics, ETH, Zürich, Switzerland
5 : Ecological and Environmental Change Research Group, Department of Biological Sciences, University of Bergen, Bergen, Norway
6 : Institute of Geosciences, Kiel University, Ludwig-Meyn-Straße 10, Kiel 24118, Germany
Source Quaternary Research (0033-5894) (Cambridge University Press (CUP)), 2021-07 , Vol. 102 , P. 130-141
DOI 10.1017/qua.2021.12
WOS© Times Cited 2
Keyword(s) Westerlies, Leeuwin Current, Planktic foraminifera, Subtropical Front, Subpolar Front

Northern and southern hemispheric influences¡ªparticularly changes in Southern Hemisphere westerly winds (SSW) and Southern Ocean ventilation¡ªtriggered the stepwise atmospheric CO2 increase that accompanied the last deglaciation. One approach for gaining potential insights into past changes in SWW/CO2 upwelling is to reconstruct the positions of the northern oceanic fronts associated with the Antarctic Circumpolar Current. Using two deep-sea cores located ¡«600 km apart off the southern coast of Australia, we detail oceanic changes from ¡«23 to 6 ka using foraminifer faunal and biomarker alkenone records. Our results indicate a tight coupling between hydrographic and related frontal displacements offshore South Australia (and by analogy, possibly the entire Southern Ocean) and Northern Hemisphere (NH) climate that may help confirm previous hypotheses that the westerlies play a critical role in modulating CO2 uptake and release from the Southern Ocean on millennial and potentially even centennial timescales. The intensity and extent of the northward displacements of the Subtropical Front following well-known NH cold events seem to decrease with progressing NH ice sheet deglaciation and parallel a weakening NH temperature response and amplitude of Intertropical Convergence Zone shifts. In addition, an exceptional poleward shift of Southern Hemisphere fronts occurs during the NH Heinrich Stadial 1. This event was likely facilitated by the NH ice maximum and acted as a coup-de-grace for glacial ocean stratification and its high CO2 capacitance. Thus, through its influence on the global atmosphere and on ocean mixing, ¡°excessive¡± NH glaciation could have triggered its own demise by facilitating the destratification of the glacial ocean CO2 state.

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Moros Matthias, de Deckker Patrick, Perner Kerstin, Ninnemann Ulysses S., Wacker Lukas, Telford Richard, Jansen Eystein, Blanz Thomas, Schneider Ralph (2021). Hydrographic shifts south of Australia over the last deglaciation and possible interhemispheric linkages. Quaternary Research, 102, 130-141. Publisher's official version : https://doi.org/10.1017/qua.2021.12 , Open Access version : https://archimer.ifremer.fr/doc/00689/80140/