Sensitivity of the Australian Monsoon to insolation and vegetation: Implications for human impact on continental moisture balance

General circulation model experiments test the geologically based correlation of high monsoon rainfall over interior Australia with Northern Hemisphere insolation and evaluate the sensitivity of the Australian Monsoon to ecosystem change. Our results suggest that Northern Hemisphere insolation control on the intensity of the Siberian High, rather than summer insolation over the Australian continent, determines the strength of the Australian Monsoon on millennial time scales, unlike a classic monsoon regime. Additional simulations show that the penetration of monsoon moisture into the interior is sensitive to biosphere-atmosphere feedbacks linked to vegetation type and soil properties. This sensitivity offers a resolution to the observed failure of the Australian Monsoon to penetrate the interior in the Holocene. Postulated regular burning practiced by early humans may have converted a tree-shrub-grassland mosaic across the semiarid zone to the modern desert scrub, thereby weakening biospheric feedbacks and resulting in long-term desertification of the continent.

[1]  W. Peltier,et al.  Ice Age Paleotopography , 1994, Science.

[2]  Rhys Jones,et al.  The human colonisation of Australia: optical dates of 53,000 and 60,000 years bracket human arrival at Deaf Adder Gorge, Northern Territory , 1994 .

[3]  J. Kutzbach,et al.  Land surface feedbacks and palaeomonsoons in northern Africa , 1998 .

[4]  R. Suppiah.  The Australian summer monsoon: a review , 1992 .

[5]  Chris S. M. Turney,et al.  Redating the onset of burning at Lynch's Crater (North Queensland): implications for human settlement in Australia , 2001 .

[6]  David Pollard,et al.  Use of a land-surface-transfer scheme (LSX) in a global climate model: the response to doubling stomatal resistance , 1995 .

[7]  S. Short,et al.  Wetting and drying of Australia over the past 300 ka , 1992 .

[8]  P. Hesse,et al.  Late Quaternary climates of the Australian arid zone: a review , 2004 .

[9]  P. Moss,et al.  Causes and consequences of long-term climatic variability on the Australian continent , 2003 .

[10]  Piers J. Sellers,et al.  A Global Climatology of Albedo, Roughness Length and Stomatal Resistance for Atmospheric General Circulation Models as Represented by the Simple Biosphere Model (SiB) , 1989 .

[11]  J. Kutzbach,et al.  Coupled climate simulation of the evolution of global monsoons in the Holocene , 2003 .

[12]  G. Miller,et al.  Continuous 150 k.y. monsoon record from Lake Eyre, Australia: Insolation-forcing implications and unexpected Holocene failure , 2004 .

[13]  S. Hastenrath,et al.  On the Prediction of India Monsoon Rainfall Anomalies , 1987 .

[14]  J. Kutzbach,et al.  The Influence of Changing Orbital Parameters and Surface Boundary Conditions on Climate Simulations for the Past 18 000 Years , 1986 .

[15]  Damian Barrett,et al.  Steady state turnover time of carbon in the Australian terrestrial biosphere , 2002 .

[16]  G. Miller,et al.  Initiation of the Australian summer monsoon 14,000 years ago , 2001 .

[17]  N. Spooner,et al.  New ages for human occupation and climatic change at Lake Mungo, Australia , 2003, Nature.

[18]  C. Tucker,et al.  Enhancement of Interdecadal Climate Variability in the Sahel by Vegetation Interaction. , 1999, Science.

[19]  P. Valdes,et al.  Insolation forcing of the Australian monsoon as controls of Pleistocene mega‐lake events , 2003 .

[20]  A. Kershaw.  Climatic change and Aboriginal burning in north-east Australia during the last two glacial/interglacial cycles , 1986, Nature.

[21]  R. DeConto,et al.  Modeling Global Climate–Vegetation Interactions in a Doubled CO2 World , 2001 .

[22]  J. Kutzbach,et al.  Vegetation and soil feedbacks on the response of the African monsoon to orbital forcing in the early to middle Holocene , 1996, Nature.

[23]  J. Nott,et al.  Plunge pools and paleoprecipitation , 1994 .

[24]  J. Charney.  Dynamics of deserts and drought in the Sahel , 1975 .

[25]  G. Laslett,et al.  New Ages for the Last Australian Megafauna: Continent-Wide Extinction About 46,000 Years Ago , 2001, Science.

[26]  McCulloch,et al.  Pleistocene extinction of genyornis newtoni: human impact on australian megafauna , 1999, Science.