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摘要
The El Nino-Southern Oscillation (ENSO) and Southern Westerly Winds (SWW) profoundly influence synoptic-scale climate in the Southern Hemisphere. Although many studies have invoked either phenomenon to explain trends in proxy data, few have demonstrated the transition from a climate dominated by SWW flow to one controlled by El Nino activity, which is postulated to have occurred after 5 cal ka BP in the mid-latitudes of the Southern Hemisphere. Tasmania, southeast Australia, is ideally situated to detect changes in both of these climatic controls. Currently, El Nino and La Nina events result in drier and wetter conditions island-wide, respectively, with the greatest impact in the north. Further, Tasmania houses north south trending mountain ranges near its western coast. As a result, areas west of the mountains exhibit a positive correlation between SWW flow and precipitation, while eastern regions possess either no or a negative relationship. Here, we present data from chironomid remains, charcoal, and geochemical proxies to investigate the paleohydrological history of Lake Dobson, a site located in Mount Field National Park, Tasmania. The proxies revealed three broad periods: (1) an early Holocene (11.5-8.3 cal kyr BP) characterised by generally high rainfall, the occurrence of irregular fires, and elevated charcoal influx at 11.4 and 10.2 cal ka BP conditions compatible with attenuated SWW flow over the site; (2) an ambiguous mid-Holocene (8.3-5 cal kyr BP) that marks the transition from a SWW- to ENSO-dominated climate; and (3) a relatively dry and stable late Holocene (5 cal kyr BP to present) that is consistent with the onset of a climate controlled by ENSO activity (i.e., characterised by a more mean El Nifio climate state). The proxy record of Lake Dobson highlights the teleconnections between the equatorial Pacific and southern Australasia.
- 出版日期2015-10-15
