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Evidence of solar and tropical ocean forcing of hydroclimate variability in south-eastern Australia for the past 6500 years
Abstract   Peer reviewed

Evidence of solar and tropical ocean forcing of hydroclimate variability in south-eastern Australia for the past 6500 years

H A McGowan, Samuel K Marx, J Soderholm and J Denholm
2010 Australasian Quaternary Association Biennial Conference: Program & Abstracts, pp.18-19
Australasian Quaternary Association (AQUA) Biennial Conference, 2010 (North Stradbroke Island, Australia, 11-Jul-2010–16-Jul-2010)
2010
url
http://aqua.org.au/View
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Abstract

Physical Geography and Environmental Geoscience solar forcing hydroclimate
Evidence of solar and tropical ocean forcing of climate cycles has been found in numerous proxy palaeoclimate records. Numerical modelling studies show physical mechanisms by which direct and indirect solar forcing may affect temperature and precipitation, while there is mounting evidence of solar forcing of tropical ocean-atmosphere decadal oscillations such as the Pacific Decadal Oscillation (PDO). We present a 6500 yr record of dust deposition from the Snowy Mountains, Australia which we have shown to be a proxy for regional hydroclimate variability. Spectral analysis of the record provides evidence of statistically significant cycles in dust deposition of 35 to 43 yrs, 62 to 73 yrs, 161 yrs (> 95% C.I.) and 2200 yrs (>90% C.I.), which correlate with phases of the PDO and variability in solar irradiance associated with the Gleissberg, Suess and Hallstattzeit solar cycles. Analysis of the spectral content of the non-stationary dust deposition time series using Morlet wavelet analyses identified the 35 yr cycle was most pronounced during the past 300 years with a trend toward a slightly longer period of 43 yrs around 250 yrs BP. This cycle also appeared to be dominant around 550 and 850 yrs BP, while the 63 to 73 yr cycle was dominant around 550, 1000 and 1500 yrs BP, and then again between 4000 to 4500 yrs BP. The longer 160 yr cycle was most pronounced during the past 1000 yrs (centered on 500 yrs BP) encompassing the Maunder, Spörer and Wolf solar minima. The results confirm that solar and tropical ocean forcing of climate at multi-decadal to millennial time scales affects the hydroclimate of southeast Australia and must be considered in predictions of future climate variability.

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