Identifying flood and drought events using a 500-year reconstruction of rainfall in the Australian subtropics as determined from hoop pine (Araucaria cunninghamii) tree rings

Subtropical Australia is highly susceptible to extreme events like the catastrophic floods that occurred in Southeast Queensland (SEQ) in 2011. This event was suggested to be a 1 in 1000 year flood, however, preliminary research of past flood deposits has indicated that a similar sized event occurred about 200 years ago. Our understanding of the past frequency of these types of events is limited because there are few long-term climate records available for this region. Historical precipitation records extend back to the 19th century, which is not of a sufficient duration to understand extreme event frequencies. Other annual proxy methods of rainfall reconstruction are needed to better understand the flood and drought history of this area. Tree rings provide an annual record of past conditions based on a single environmental variable that is limiting tree growth. Here we present the first long-term (>150 years) Australian subtropical tree ring reconstruction of rainfall from Lamington National Park, a natural area of rainforest on the southern boundary of SEQ. Hoop Pine (Araucaria cunninghamii) trees were used as they are one of the longest lived tree species in subtropical Australia, they grow in response to precipitation conditions, and they put on a visible annual ring that can be measured. This record was developed using a multi-technique approach where traditional ring width measuring, X-ray densitrometry, and radiocarbon dating were combined to create a robust chronology that was then used to reconstruct rainfall. Years with major rainfall events are confirmed through Calcium and Strontium signals identified in the tree rings using ITRAX XRF trace elements. Climate conditions for years with known flood and drought events were then compared to our reconstruction to identify potential extreme events in SEQ beyond the period of instrumental record. The methodology, results, and future directions of this research will be discussed.

Keywords

Floods, Droughts, Rain, Australia, Pines, Isotope dating

Citation

Haines, H. A., English, N. B., Olley, J. M, Hua, Q., Heijnis, H., & Palmer, J. G. (2015). Identifying flood and drought events using a 500-year reconstruction of rainfall in the Australian subtropics as determined from hoop pine (Araucaria cunninghamii) tree rings. Paper presented at the XIX INQUA Congress Quaternary Perspectives on Climate Change, Natural Hazards and Civilization 26 July - 2 August, 2015, in Nagoya, Japan

URI

http://inqua2015.jp/program/INQUA2015program.pdf
http://apo.ansto.gov.au/dspace/handle/10238/6822

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