HR: 0800h
AN: PP11B-0528    [Abstracts]
TI: Enhanced Circulation of the Miocene Australian Monsoon System
AU: Herold, N
EM: nicholas.herold@geosci.usyd.edu.au
AF: University of Sydney, School of Geosciences, Building H11, University of Sydney, Sydney, NSW 2006, Australia
AU: You, Y
EM: you@geosci.usyd.edu.au
AF: University of Sydney, School of Geosciences, Building H11, University of Sydney, Sydney, NSW 2006, Australia
AU: * Muller, D
EM: dietmar@geosci.usyd.edu.au
AF: University of Sydney, School of Geosciences, Building H11, University of Sydney, Sydney, NSW 2006, Australia
AU: Sdrolias, M
EM: marias@geosci.usyd.edu.au
AF: University of Sydney, School of Geosciences, Building H11, University of Sydney, Sydney, NSW 2006, Australia
AB: Paleo-botanical studies in central Australia have revealed periods of distinct seasonality throughout the Tertiary, prior to existing monsoon sedimentary records. Despite advances in the mechanisms and timing of the Australian summer monsoon, its history has remained largely unconstrained. We use the National Center for Atmospheric Research (NCAR) Community Atmosphere Model (CAM) and Community Land Model (CLM) to simulate the middle Miocene and modern Australian monsoon. Results show that southward displacement of the Australian continent in the Miocene produces higher precipitation over the monsoon trough and decreased precipitation over northern Australia. Location of precipitation maxima, sea-level pressure minima and the monsoon shear line indicates that the monsoon trough has not moved markedly between the Miocene and present. Existence of larger and warmer seas north of Australia in the Miocene, in conjunction with a more intense monsoon trough, suggests that Australia's equator ward drift has had a dampening effect on monsoon trough intensity via reduced moisture availability. Drift of the Australian continent into the zone of influence of the monsoon trough challenges classic textbook theory that high insolation over the Australian land mass is a dominant driver of the monsoon. Existence of monsoon climates significantly older than the middle Miocene therefore would most likely be driven by a classical land-sea temperature gradient as opposed to a southward reaching Inter Tropical Convergence Zone.
DE: 1610 Atmosphere (0315, 0325)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1626 Global climate models (3337, 4928)
DE: 1631 Land/atmosphere interactions (1218, 1843, 3322)
DE: 1637 Regional climate change
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting