Aus2k

The Australasian region covers a vast number of ecosystems and provides a diverse range of paleoenvironmental and climatic archives

about Aus2k

Australasia spans from the tropics to the sub-Antarctic, straddling several major oceanographic and atmospheric systems that are of global significance and potentially sensitive to anthropogenic-driven climate change. For instance, northern Australasia is influenced by the Indo–Pacific Warm Pool, which is a major source of latent heat and hence drives global atmospheric (Pierrehumbert, 2000) and oceanic (Hansen et al., 2006) circulation. Towards higher latitudes, the Southern Ocean (south of 45˚S) plays a key role in global climate (Caldeira and Duffy, 2000). Over the late Pleistocene, atmospheric CO₂ concentration and Antarctic temperatures appear to be strongly coupled (Siegenthaler et al., 2005), suggesting the former are driven by changes in oceanic and atmospheric circulation across the region (Toggweiler et al., 2006). This is of considerable concern under scenarios for future climate change, where an increasingly poleward shift and intensification of westerly airflow during the 21^st century could significantly reduce the Southern Ocean uptake of anthropogenically produced CO₂ (Le Quére et al., 2007). 

Unfortunately, the spatial distribution of historical datasets is highly variable across the region where most records only began in the 20^th Century (Nicholls et al., 2006). Although considerable progress has been made in developing a robust quantified reconstructions of temperature change for the northern hemisphere over the past two millennia (Mann et al., 2008), significantly more work is required in Australasia (and the southern hemisphere as a whole). This information is required to develop a critical baseline against which to compare present and future warming (National Research Council, 2006). Developing a record of past precipitation requires even greater effort and is of particular importance to Australia (being the driest inhabited continent in the world). There is currently a dearth of moisture-sensitive records, though promising progress has recently been made in developing annually resolved records through the careful selection of suitably sensitive tree species (Heinrich et al., 2008) and luminescence banding within corals (representing past freshwater river flow and Queensland rainfall; Lough, 2007).

The PAGES Working Group on Australasian climate during the last two millennia (Aus2k) was launched in July 2007 to generate and synthesize high-resolution paleoclimate data to assess and elucidate both the timing and variability of the Australasian climate change during this period (Turney et al., 2008).

Working Group Leader: Chris Turney

References
Caldeira, K. and Duffy, P.B., 2000: The role of the Southern Ocean in uptake and storage of anthropogenic carbon dioxide, Science, 287: 620-622.
Hansen, J., Sato, M., Ruedy, R., Lo, K., Lea, D.W. and Medina-Elizade, M., 2006: Global temperature change, Proceedings of the National Academy of Sciences, 103: 14288-14293.
Heinrich, I., Weidner, K., Helle, G., Vos, H. and Banks, J.C.G., 2008: Hydroclimatic variation in far north Queensland since 1860 inferred from tree rings, Palaeogeography, Palaeoclimatology, Palaeoecology, 270: 116-127.
Le Quére, C., et al., 2007: Saturation of the Southern Ocean CO₂ sink due to recent climate change, Science, 316: 1735-1738.
Lough, J.M., 2007: Tropical river flow and rainfall reconstructions from coral luminescence: Great Barrier Reef, Paleoceanography, 22: doi:10.1029/2006PA001377.
Mann, M.E., Zhang, Z., Hughes, M.K., Bradley, R.S., Miller, S.K., Rutherford, S. and Ni, F., 2008: Proxy-based reconstructions of hemispheric and global surface temperature variations over the past two millennia, Proceedings of the National Academy of Sciences, 105: 13252-13257.
National Research Council, 2006: Surface Temperature Reconstructions for the Last 2,000 Years, National Academy of Sciences, The National Academies Press, Washington.
Nicholls, N., Collins, D., Trewin, B. and Hope, P., 2006: Historical instrumental climate data for Australia-Quality and utility for palaeoclimatic studies, Journal of Quaternary Science, 21: 681-688.
Pierrehumbert, R.T., 2000: Climate change and the tropical Pacific: The sleeping dragon awakes, Proceedings of the National Academy of Sciences, 97: 1355-1358.
Siegenthaler, U. et al., 2005: Stable carbon cycle-climate relationship during the late Pleistocene, Science, 310, 1313-1317.
Toggweiler, J.R., Russell, J.L. and Carson, S.R., 2006: Mid-latitude westerlies, atmospheric CO₂, and climate change during the ice ages, Paleoceanography, 21: doi:10.1029/2005PA001154.
Turney, C.S.M., Duncan, R., Nicholls, N., Moberg, A. and Pollack, H., 2008: Towards an Australasian climate reconstruction for the past two millennia, PAGES News, 16(2): 34.