No abstract

The prevailing view in the palaeoclimate literature of the last 20 years is that the Southern Westerly Winds (SWW) were intensified over southern Australia and Tasmania during the warmer-than-present early Holocene (11e8 ka). At similar latitudes on the opposite side of the southern mid-latitudes, palaeoclimate studies have suggested a poleward shift of the northern edge of the westerlies and focusing at 49 S in southern South America. This zonal asymmetry contrasts with the modern day zonal symmetry displayed by the SWW and poses a formidable challenge to an understanding of the modes of climatic variability of the southern extra-tropics. This paper presents an updated synthesis of continuous, radiocarbon-dated palaeoenvironmental data from the westerlies zone of influence in all Southern Hemisphere continents. Synchronous multi-millennial trends in moisture, vegetation, fire, and hydrologic balance are remarkably consistent with the way the SWW changes impact upon the climate in Southern Hemisphere landmasses in the modern climate. Considering the modern relationships between local precipitation and zonal wind speeds, it is suggested that the SWW changed in a zonally symmetric manner at multi-millennial scale between 14 and 5 ka. Regional asymmetry develops after 5 ka across the Southern Hemisphere, with a pattern of precipitation anomalies akin to the modern functioning of El Niño e Southern Oscillation, which started ~6200 years ago.Institute of Ecology and Biodiversity, Chile, and Fondecyt 311018

Dosseto, A. (2013). Climatic records over the past 30 ka from temperate Australia -a synthesis from the Oz-INTIMATE workgroup. Quaternary Science Reviews, 74 58-77.Climatic records over the past 30 ka from temperate Australia -a synthesis from the Oz-INTIMATE workgroup AbstractTemperate Australia sits between the heat engine of the tropics and the cold Southern Ocean, encompassing a range of rainfall regimes and falling under the influence of different climatic drivers. Despite this heterogeneity, broad-scale trends in climatic and environmental change are evident over the past 30 ka. During the early glacial period (∼30-22 ka) and the Last Glacial Maximum (∼22-18 ka), climate was relatively cool across the entire temperate zone and there was an expansion of grasslands and increased fluvial activity in regionally important Murray-Darling Basin. The temperate region at this time appears to be dominated by expanded sea ice in the Southern Ocean forcing a northerly shift in the position of the oceanic fronts and a concomitant influx of cold water along the southeast (including Tasmania) and southwest Australian coasts. The deglacial period (∼18-12 ka) was characterised by glacial recession and eventual disappearance resulting from an increase in temperature deduced from terrestrial records, while there is some evidence for climatic reversals (e.g. the Antarctic Cold Reversal) in high resolution marine sediment cores through this period. The high spatial density of Holocene terrestrial records reveals an overall expansion of sclerophyll woodland and rainforest taxa across the temperate region after ∼12 ka, presumably in response to increasing temperature, while hydrological records reveal spatially heterogeneous hydro-climatic trends. Patterns after ∼6 ka suggest higher frequency climatic variability that possibly reflects the onset of large scale climate variability caused by the El Niño/Southern Oscillation. Petherick, L., Bostock, H., Cohen, T. J., Fitzsimmons, K., Tibby, J., Fletcher, M. -S., Moss, P., Reeves, J., Mooney, S., Barrows, T., Kemp, J., Jansen, J., Nanson, G. & Dosseto, A. (2013). Climatic records over the past 30 ka from temperate Australia -a synthesis from the Oz-INTIMATE workgroup. Quaternary Science Reviews, 74 58-77. Australian coasts. The deglacial period (~18-12 ka) was characterised by glacial recession and eventual disappearance resulting from an increase in temperature deduced from terrestrial records, while there is some evidence for climatic reversals (e.g. the Antarctic Cold Reversal) in high resolution marine sediment cores through this period. The high spatial density of Holocene terrestrial records reveals an overall expansion of sclerophyll woodland and rainforest taxa across the temperate region after ~12 ka, presumably in response to increasing temperature, while hydrological records reveal spatially heterogeneous hydro-climatic trends. Patterns after ~6 ka suggest higher frequency climatic variability that possibly reflects the onset of large scale climate variability caused by...