Continuous 150 k.y. monsoon record from Lake Eyre, Australia: Insolation-forcing implications and unexpected Holocene failure

Abstract

Our reconstructed history of Lake Eyre provides the first continuous continental proxy record of Australian monsoon intensity over the past 150 k.y. This continental record's broad correspondence to the marine isotope record demonstrates that this very large catchment, with its hydrology dependent on a planetary-scale climate element, responds to Milankovitch-scale climate forcing. Abrupt transitions from dry phases to wet phases (ca. 125 and 12 ka) coincide with Northern Hemisphere winter insolation minima rather than Southern Hemisphere summer insolation maxima, indicating that Northern Hemisphere insolation exerts a dominant control over the intensity of the Australian monsoon. Stratigraphic and dating uncertainties of other wet phases preclude conclusive correlation to specific insolation signals but, within the uncertainties, are consistent with Northern Hemisphere forcing. Regardless of the hemispheric forcing, the low intensity of the early Holocene Australian monsoon-by comparison with the last interglacial and particularly the last high-level lacustrine event at 65-60 ka when all forcing elements were modestis an enigma that can be explained by a change in boundary conditions within Australia.

Extinction implications of a chenopod browse diet for a giant Pleistocene kangaroo

“…However, droughts have characterized the Australian interior for at least 7 million years (27) and P. goliah (and many other Pleistocene megafaunal species) survived multiple Pleistocene periods of higher aridity, including the penultimate glacial and last interglacial (5,6,28,29). Moreover, effective rainfall in southern, eastern, and inland Australia was not markedly diminished until after 40 kyr ago (30)(31)(32). This is well after the demise of P. goliah and many other megafaunal taxa (including water-efficient grazing species) 50-45 kyr ago (2,6) and well before the onset of arid conditions marking the last glacial maximum 27-17 kyr ago (29).…”

Altered Ecologies: Fire, climate and human influence on terrestrial landscapes: Terra Australis 32

“…Bowler and Hamada 1971;Chen et al 1993;Bowler et al 2001;Magee et al 2004,), speleothems (Ayliffe et al 1998) sand dunes and dust (Ash and Wasson 1983;Wasson 1983;Hesse et al 2003), and vegetation all indicates that cold conditions at the Last Glacial Maximum were accompanied by a drier climate. Quantitative estimates of rainfall change are less amenable to precise delineation than palaeotemperature, as analyses of palaeo-water balance are complicated by interactions between precipitation, temperature, wind velocity and vegetation cover.…”

Late Quaternary evolution of a playa margin at Lake Frome, South Australia

“…Peak highstands with maximum water depths of ~20-25 m and >15 m at Lake Eyre and Lake Frome/Callabonna, respectively, occurred exclusively in the first half of the last glacial cycle prior to ~50 ka , while no significant evidence for filling events has been reported from Lake Eyre during the last 45 -50 ka Magee and Miller, 1998;Magee et al, 2004). In contrast, successively younger and lower lake levels are recorded around the southernmost internally draining playa lakes Frome and Callabonna during the same time Cohen et al, 2011), raising the question if this divergence could result from regionally differing responses to lake-specific hydrologic boundary conditions and thresholds (Benson and Paillet, 1989;Cohen et al, 2012), or may in fact reflect significant changes in runoff and/or precipitation sources related to large-scale shifts in atmospheric circulation pattern .…”

“…A variety of differing luminescence techniques have been applied in dating aeolian, fluvial, littoral, and lacustrine sediments in arid Central Australia (e.g. Magee et al, 2004;Cohen et al, 2011;Cohen et al 2012). A recent inventory of OSL and TL ages from Central Australia shows that there are no systematic differences with regard to absolute and relative standard errors between the two methods (n=130), and there is very good agreement between duplicate TL and OSL samples (n=20).…”

“…Early studies made use of discontinuous lacustrine sedimentary archives in the central parts of the lake basins to infer changes in depositional environments over time (Bowler et al, 1986;Magee et al, 1995). The chronology and sedimentology of shoreline, fluvial and aeolian sediments has been used to indicate that these dry playa lakes in the now arid centre of Australia had repeatedly filled to form a continuous water body or mega-lake with a maximum extent of nearly 35,000 km 2 (DeVogel et al, 2004;Leon and Cohen, 2012;Magee et al, 2004).…”