HR: 12:05h
AN: PP21D-08    [PDF]
TI: A Paleoclimate Record of the Great Australian Bight Provides Tropical-Extratropical Linkage for the Past 18,000 Years
AU: * Andres, M S
EM: mandres@rsmas.miami.edu
AF: University of Miami RSMAS/MGG, 4600 Rickenbacker Causeway, Miami, FL 33149 United States
AU: * Andres, M S
EM: mandres@rsmas.miami.edu
AF: Geological Institute ETH Zurich, ETH-Zentrum, Sonneggstr. 5, Zurich, 8092 Switzerland
AU: Bernasconi, S M
EM: stefano@erdw.ethz.ch
AF: Geological Institute ETH Zurich, ETH-Zentrum, Sonneggstr. 5, Zurich, 8092 Switzerland
AU: McKenzie, J A
EM: sediment@erdw.ethz.ch
AF: Geological Institute ETH Zurich, ETH-Zentrum, Sonneggstr. 5, Zurich, 8092 Switzerland
AU: Roehl, U
EM: uroehl@rcom-bremen.de
AF: Geoscience Department, Reseach Center for Ocean Margins, Bremen University, PO Box 330440, Bremen, 82334 Germany
AB: Present climate in southern Australia is dominated by the strength and position of the subtropical high-pressure belt (STHB) and mid-latitude Westerlies. The STHB, in turn, is powered by the position and strength of the Intertropical Convergence Zone (ITCZ). Shifts in strength and position of either the STHB or Westerlies, results in significant changes of rainfall over southern Australia. A sediment core from the Great Australian Bight (GAB) is used to evaluate the position, strength and influence of these climate regimes during the past 18,000 years. ODP Leg 182 Site 1127 provides a record with high sedimentation rates and abundant planktic foraminifers allowing a 14C-dated chronology and paleoceanographic reconstruction. Its coastal proximity links the terrestrial and oceanic climate evolution using the sedimentary iron content. Iron is a major constituent of dust and only reaches the GAB if entrained in pre-frontal northerly dust plumes that are subsequently scavenged by precipitation related to westerly low-pressure systems over the Bight. Very little iron reached the GAB during the last glacial maximum when strong Westerlies blew dust offshore into the Tasman Sea and Southern Ocean. Stepwise deglacial warming and increasing dust deposition reversed during the Younger Dryas implying a return to dry and windy conditions. High Fe values during the early Holocene coincide with warm and wet conditions related to low summer insolation and reduced seasonality. Reduced ITCZ migration south allowed for northerly penetration of rainbearing Westerlies. In contrast, decreasing Fe input since ~7000 years coincides with aridification related to increasing seasonality and large latitudinal migration of the ITCZ. Holocene climate variability is the result of insolation-driven seasonality producing the large-scale features of atmospheric circulation and climate characteristics of southern Australia today. Sensitive to changing influence of Westerlies and Hadley circulation, this record provides evidence for a tropical-extratropical teleconnection.
DE: 1600 GLOBAL CHANGE (New category)
DE: 1620 Climate dynamics (3309)
DE: 3344 Paleoclimatology
DE: 9330 Australia
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting