147-15 Understanding the Orbital to Millennial-Scale Variability of the Southern Hemisphere Westerly Winds: Biomarker Reconstructions from the North Island of New Zealand

Session: Climate, Ocean and Environmental Changes Through Earth History: From Marine and Terrestrial Proxies to Model Assessments (Posters)

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From heat transfer to storm regulation, the Southern Hemisphere westerly winds (SHWW) play a key role in the global climate by balancing climate perturbations between the high and low latitudes. On glacial timescales, the latitudinal position of the SHWW has major implications for Southern Ocean CO₂ storage, making them an essential feedback mechanism for past changes in global climate. While studies have suggested that the westerlies vary in position and intensity in response to orbital and millennial-scale forcings, climate models and proxy data disagree about the nature of the SHWW responses to orbital forcings and glacial boundary conditions. Our knowledge of the SHWW is further limited due to the lack of well-dated, unambiguous proxy indicators. To address these uncertainties, we generated a continuous 130-kyr long, high-resolution proxy reconstruction of the SHWW from Orakei Basin and Lake Pupuke, located on the North Island of New Zealand, using the hydrogen isotope composition of sedimentary leaf waxes as a proxy for Southern Hemisphere moisture sources associated with changes in the position of the SHWW. We complement these data with temperature reconstructions using the MBT’_5ME index. The temperature record shows a rapid cooling of 3^oC transitioning out of the Eemian, then remains relatively stable throughout most of the last glacial, with minimum temperatures centered on ca. 70-ka and during the Last Glacial Maximum. On orbital timescales, temperature and dD_wax variations are broadly synchronous with Antarctic temperature changes, reflecting the influence of large-scale, global climate processes on the position and strength of SHWW. However, on millennial timescales and during the deglaciation, their agreement weakens, suggesting important differences in the controls of the SHWW and temperature on these timescales. These findings highlight the complex, time-scale dependent nature of the SHWW, emphasizing their role in modulating regional hydroclimate and contributing to global climate feedbacks across glacial-interglacial timescales.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-11131

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