A 250-year periodicity in Southern Hemisphere westerly winds over the last 2600 years

Turney, C. S.M., Jones, R. T., Fogwill, C., Hatton, J., Williams, A. N., Hogg, A., Thomas, Z. A., Palmer, J., Mooney, S. and Reimer, R. W. (2016) A 250-year periodicity in Southern Hemisphere westerly winds over the last 2600 years. Climate of the Past, 12 (2), 189-200. (doi:10.5194/cp-12-189-2016).

Abstract

Southern Hemisphere westerly airflow has a significant influence on the ocean-atmosphere system of the mid-to high latitudes with potentially global climate implications. Unfortunately, historic observations only extend back to the late 19th century, limiting our understanding of multi-decadal to centennial change. Here we present a highly resolved (30-year) record of past westerly wind strength from a Falkland Islands peat sequence spanning the last 2600 years. Situated within the core latitude of Southern Hemisphere westerly airflow (the so-called furious fifties), we identify highly variable changes in exotic pollen and charcoal derived from South America which can be used to inform on past westerly air strength. We find a period of high charcoal content between 2000 and 1000. BP, associated with increased burning in Patagonia, most probably as a result of higher temperatures and stronger westerly airflow. Spectral analysis of the charcoal record identifies a pervasive ca. 250-year periodicity that is coherent with radiocarbon production rates, suggesting that solar variability has a modulating influence on Southern Hemisphere westerly airflow. Our results have important implications for understanding global climate change through the late Holocene.

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Contributors

Author: Z. A. Thomas

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