2000 Years of Southern Hemisphere Climate Variability: King Billy Pine and the Southern Annular Mode

Authors: Amy Hessl*, West Virginia University, Kathryn Allen, University of Melbourne, Scott Nichols, University of Melbourne, Patrick Baker, University of Melbourne, Tessa Vance, University of Tasmania
Topics: Paleoenvironmental Change, Climatology and Meteorology, Biogeography
Keywords: dendrochronology, climate dynamics, Australia
Session Type: Paper
Day: 4/6/2019
Start / End Time: 1:10 PM / 2:50 PM
Room: Marshall East, Marriott, Mezzanine Level
Presentation File: No File Uploaded

The Southern Annular Mode (SAM) is the leading mode of climate variability in the middle to high latitudes of the Southern Hemisphere where it affects the strength and position of the westerly winds. Existing reconstructions of the SAM are dependent on terrestrial proxies located in the Pacific sector while SAM in the Indian Ocean sector is poorly understood. King Billy pine (Athrotaxis selaginoides) trees located on subalpine ridges in southern Tasmania, Australia have the potential to fill a critical gap in our understanding of Southern Hemisphere climate variability, particularly in the Indian Ocean sector. King Billy pine trees produce annual rings, are long-lived (up to 1000 years), and because they grow at high elevations with ample moisture, annual growth is limited by temperature. Here we use >350 living and dead (sub-fossil) wood samples collected from seven sites in southern Tasmania to generate a 2000-year King Billy pine chronology. We compare this network with gridded climate data, including growing season temperature and atmospheric pressure over land and sea (1959-2011), to demonstrate that these data can be used to develop a multi-millennial reconstruction of the SAM for the Indian Ocean sector. Further, we show that this King Billy pine network complements another emerging source of high-resolution paleoclimate data from East Antarctic ice. A new reconstruction, centered on the Indian Ocean sector would address uncertainties in existing SAM reconstructions from the Pacific sector and refine our understanding of internal dynamics of Southern Hemisphere climate prior to human modifications of the atmosphere.

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