Elsevier

Quaternary Science Reviews

Volume 56, 21 November 2012, Pages 167-171
Quaternary Science Reviews

Short communication
A pluvial episode identified in arid Australia during the Medieval Climatic Anomaly

https://doi.org/10.1016/j.quascirev.2012.09.021Get rights and content

Abstract

Optically stimulated luminescence (OSL) ages from a relict shoreline on Lake Callabonna record a major pluvial episode in southern central Australia between 1050 ± 70 and 1100 ± 60 Common Era (CE), within the Medieval Climatic Anomaly (MCA). During this pluvial interval Lake Callabonna filled to 10–12 times the volume of the largest historical filling (1974) and reached maximum depths of 4–5 m, compared to the 0.5–1.0 m achieved today. Until now there has been no direct evidence for the MCA in the arid interior of Australia. A multi-proxy, analogue-based atmospheric circulation reconstruction indicates that the pluvial episode was associated with an anomalous meridional atmospheric circulation pattern over the Southern extratropics, with high sea-level pressure ridges in the central Indian Ocean and Tasman Sea, and a trough extending from the Southern Ocean into central Australia. A major decline in the mobility of the Australian aboriginal hunter-gatherer coincides with this MCA period, in southern central Australia.

Introduction

The Medieval Climatic Anomaly (950–1250 CE) has classical climatic connotations for the Northern Hemisphere (e.g. severe drought in North America, Feng et al., 2008) and associated cultural developments (e.g. the settlement of Iceland and Greenland at ∼CE 874 and ∼CE 985, respectively; Xoplaki et al., 2011). A number of studies have examined the temporal and regional variation in the MCA for different regions, although almost exclusively within the Northern Hemisphere, and with no robust evidence for MCA hydroclimate impacts in Australasia. This time interval is however particularly notable in continental Australia because recent archaeological evidence suggests a rapid expansion in human population during and following the MCA (Smith and Ross, 2008; Williams et al., 2010). However, the role of climate in this expansion remains to be determined, and unlike the situation in the Northern Hemisphere, little is known as to whether this interval was warm, wet, cool or dry.

At a global scale, major shifts in climate at this time are hypothesised to be a result of a strongly positive North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation (AMO) (Trouet et al., 2009), together with a shift towards a La Niña-like mean state in the Pacific (Clement et al., 1996; Mann et al., 2009). We assess the nature and timing of a major pluvial episode in southern central Australia that corresponds to the MCA by excavating relict shorelines and dating them with a range of independent dating techniques. We also examine the association between the hydrology and atmospheric circulation in southern central Australia.

Section snippets

Regional setting and methods

Lake Callabonna is part of the Lake Mega-Frome system (Lakes Frome, Callabonna, Blanche and Gregory, Fig. 1), which coalesces at 5 ± 2 m depth to form a single major waterbody surrounding the eastern and northern margins of the Flinders Ranges in arid central Australia (Fig. 1). These playa lakes have lake-floor elevations that range from −2 to +1 m Australian Height Datum (AHD – equivalent to mean height above sea level). Historically, Lakes Frome and Callabonna have filled to depths of

Chronology of the Lake Callabonna relict shorelines

The lake margin transect represents a relatively steep margin with four prominent shorelines above the modern floor, dissected by modern streams (Fig. 1). Five excavations were undertaken to supplement the original stratigraphic section undertaken by Cohen et al., 2011, Cohen et al., 2012 to test the validity of the initial MCA chronology. The additional stratigraphic sections confirm the presence of a 0.5–0.6 m thick beach unit from the lowest shoreline, which is 4 ± 0.2 m above the playa

Discussion and conclusion

Shoreline evidence for an MCA pluvial episode at Lake Callabonna is supported by studies documenting high-magnitude flooding in rivers draining the central Australian ranges (Pickup et al., 1988; Patton et al., 1993), the Barrier Ranges ∼150 km to the east of Lake Frome (Jansen and Brierley, 2004), and the Flinders Ranges, where at least one major flood has occurred since 300 CE (Quigley et al., 2007). Unlike the Flinders Ranges and Barrier Ranges, no record of major flooding occurs along the

Acknowledgements

This research was undertaken as part of ARC Discovery funding (DP1096911) to GCN and TJC. We would like to thank Gerard and Karina Sheehan of Moolwatana homestead for their hospitality and access to sites. We also thank the reviewers for improving the quality of the manuscript.

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