A northward shift of the southern westerlies during the Antarctic cold reversal: evidence from Tasmania
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Date
2018-12-10
Journal Title
Journal ISSN
Volume Title
Publisher
Australasian Quaternary Association
Abstract
The Last Glacial Termination (LGT) was interrupted in the Southern Hemisphere by the Antarctic
Cold Reversal (ACR; 14.7 to 13 ka), a millennial-scale cooling event that coincided with the Bølling–
Allerød warm phase in the North Atlantic (14.7 to 12.7 ka). This inter-hemispheric asynchrony of
climate change through the LGT, the bipolar seesaw, has been theoretically linked to latitudinal
shifts in the southern westerly wind belt (SWW) and their proposed influence over the global carbon
cycle via wind-driven upwelling of CO2 rich deep waters in the Southern Ocean (SO). However, while
climate models and theory predict a northward shift of the SWW during the ACR in response to
ocean-atmosphere heat dynamics, proxy-based reconstructions disagree on the behaviour of the
SWW through this interval, and the role of the SWW during the LGT remains contested. Here we
present terrestrial proxy palaeoclimate data (pollen, μXRF geochemistry, charcoal) from multiple
lakes across Tasmania (40-44⁰S), an island located at the northern edge of the SWW. Our data
reveal a clear SWW increase over Tasmania during the ACR, synchronous with reduced SWW-driven
upwelling in the SO at the southern edge of the SWW. When combined with evidence from
Antarctic ice cores and terrestrial records from New Zealand and Patagonia our results suggest a
hemisphere-wide migration of the SWW during the LGT, lending support to the hypothesis that
changes in wind-driven ventilation of CO2 from the Southern Ocean were a key driver of the global
carbon cycle during the LGT. © The Authors.
Description
Keywords
Wind, Tasmania, Quaternary period, Cooling, Southern Hemisphere, Climatic change, Pollen, Charcoal, Antarctica, New Zealand, Drill cores
Citation
Alexander, J., Fletcher, M.-S., Pedro, J., Mariani, M., Beck, K., Blaauw, M., Hodgson, D., Heijnis, H., Gadd, P., & Lise-Pronovost, A. (2018). A northward shift of the southern westerlies during the Antarctic cold reversal: evidence from Tasmania. Paper presented at the AQUA Biennial Conference, Canberra, 10-14th December 2018. (pp. 61). Retrieved from: https://aqua.org.au/wp-content/uploads/2019/10/AQUA-2018-Program.pdf