[A-CG32] Extratropical oceans and atmosphere

[ACG32-P11] Effects of regional and global climate on beryllium isotopes from Lake Selina, Western Tasmania communicated via the Southern Westerly Winds

*Bethany C. Behrens¹, Agathe Lise-Pronovost^2,3, Michael-Shawn Fletcher², Yasuto Watanabe⁴, Takahiro AZE⁵, Yosuke Miyairi⁵, Yusuke Yokoyama^5,6,7,8,9 (1.Graduate School of International Resource Science, Akita University, Japan, 2.School of Geography, Earth and Atmospheric Sciences, University of Melbourne, Australia, 3.The Australian Archaeomagnetism Laboratory, Paleoscience Labs, Department of Archaeology and History, La Trobe University, Melbourne Campus, Australia, 4.Japan Meteorological Agency, Global Atmosphere and Ocean Research Department, Japan, 5.Atmosphere and Ocean Research Institute, The University of Tokyo, Japan, 6.Department of Earth and Planetary Sciences, Graduate School of Science, The University of Tokyo, Japan, 7.Graduate Program on Environmental Sciences, The University of Tokyo, Japan, 8.Department of Biogeochemistry, Japan Agency for Marine-Earth Science and Technology, Japan, 9.Research School of Physics, The Australian National University, Canberra, Australia)

Keywords:Southern Hemisphere, Tasmania, beryllium isotopes, Southern Westerly Winds, glacial-interglacial cycles

The strength of the Southern Westerly Winds affects precipitation in the Southern Hemisphere. In western Tasmania, a strengthening of Southern Westerly Winds is associated with an increase in precipitation, including at our study site, Lake Selina (Lise-Pronovost et al., 2021). Lake Selina is located at 42°S, where the vegetation band displays a strong response to present-day changes in the position and intensity of the Southern Westerly Winds (Gillett et al., 2006). The lacustrine sediment contains a record extending to at least the Penultimate Glacial Maximum. The lake was not glaciated during the Last Glacial Period and therefore contains a record of the climatic transition from the Last Glacial Period through the deglacial Period to the present. Here, the longest known continuous record of ice advance and retreat in Tasmania during the last glacial period is assessed using beryllium-10 and beryllium-9 isotope ratio (¹⁰Be/⁹Be).

There are few studies using ¹⁰Be/⁹Be in lacustrine settings. Those include using ¹⁰Be/⁹Be as an indicator of lake level changes (Kim et al., 2012, McHargue et al., 2011), precipitation (Cao et al., 2023), paleomagnetic field changes (Nillsson et al., 2011; Lisé-Pronovost et al., 2021), and regional glacier dynamics in Antarctica (Sproson et al., 2021b). Changes in the Southern Westerly Winds may strongly affect beryllium isotope variations due to the close relationship of wind with precipitation and dust deposited directly into the lake and catchment area. Furthermore, shifts in Southern Ocean fronts and increased/decreased sea surface temperature are correlated to environmental variations, a signal which may be translated into the lacustrine sediment record. By examining these elements, the factors which influence ¹⁰Be/⁹Be will be assessed. Taking into consideration multiple climatic proxies and new model results, here we elucidate the environmental factors affecting beryllium isotope deposition from ca. 125 ka BP and their relationship to the Southern Westerly Winds.