Evolution of late pleistocene and holocene climates in the circum-south pacific land areas |
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| Authors: | Vera Markgraf John R Dodson A Peter Kershaw Matt S McGlone Neville Nicholls |
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| Institution: | (1) Institute of Arctic and Alpine Research, University of Colorado, 80309-450 Boulder, CO, USA;(2) School of Geography, University of New South Wales, 2033 Kensington, New South Wales, Australia;(3) Department of Geography and Environmental Science, Monash University, 3168 Clayton, Victoria, Australia;(4) D.S.I.R. Land Resources, Private Bag, Christchurch, New Zealand;(5) Bureau of Meteorology, GPO Box 1289K, 3001 Melbourne, Victoria, Australia |
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| Abstract: | Paleovegetation maps were reconstructed based on a network of pollen records from Australia, New Zealand, and southern South America for 18 000, 12000, 9000, 6000, and 3000 BP and interpreted in terms of paleoclimatic patterns. These patterns permitted us to speculate on past atmospheric circulation in the South Pacific and the underlying forcing missing line mechanisms. During full glacial times, with vastly extended Australasian land area and circum-Antarctic ice-shelves, arid and cold conditions characterized all circum-South Pacific land areas, except for a narrow band in southern South America (43° to 45°S) that might have been even wetter and moister than today. This implies that ridging at subtropical and mid-latitudes must have been greatly increased and that the storm tracks were located farther south than today. At 12000 BP when precipitation had increased in southern Australia, New Zealand, and the mid-latitudes of South America, ridging was probably still as strong as before but had shifted into the eastern Pacific, leading to weaker westerlies in the western Pacific and more southerly located westerlies in the eastern Pacific. At 9000 BP when, except for northernmost Australia, precipitation reached near modern levels, the south Pacific ridges and the westerlies must have weakened. Because of the continuing land connection between New Guinea and Australia, and reduced seasonality, the monsoon pattern had still not developed. By 6000 BP, moisture levels in Australia and New Zealand reached their maximum, indicating that the monsoon pattern had become established. Ridging in the South Pacific was probably weaker than today, and the seasonal shift of the westerlies was stronger than before. By 3000 BP essentially modern conditions had been achieved, characterized by patterns of high seasonal variability.Contribution to Clima Locarno — Past and Present Climate Dynamics; Conference September 1990, Swiss Academy of Sciences — National Climate Program |
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