HR: 08:45h
AN: PP21A-04 INVITED     [PDF]
TI: Variability in the Mean Latitude of the Atlantic ITCZ as Recorded in Cariaco Basin Sediments
AU: * Peterson, L C
EM: lpeterson@rsmas.miami.edu
AF: RSMAS - University of Miami, 4600 Rickenbacker Cswy., Miami, FL 33149 United States
AU: Haug, G H
EM: haug@gfz-potsdam.de
AF: Geoforschungzentrum Potsdam, Telegrafenberg, Potsdam, D-14473 Germany
AU: Lea, D W
EM: lea@geol.ucsb.edu
AF: UC Santa Barbara, Dept. of Geological Sciences, Santa Barbara, CA 93106 United States
AU: Hughen, K A
EM: khughen@whoi.edu
AF: Woods Hole Oceanographic Institution, MS#25, Woods Hole, MA 02543 United States
AB: Climate variability in the tropical Atlantic is largely forced by changes in the strength and position of the Intertropical Convergence Zone (ITCZ). The Cariaco Basin, located on the northern margin of Venezuela, is sensitive to tropical Atlantic climate change and its sediments provide a record of past ITCZ behavior. Today, the Cariaco Basin has two distinct seasons that reflect the annual migration of the ITCZ. Between January-March, when the ITCZ lies south near the equator, northeasterly trade winds sit directly overhead Cariaco Basin and coastal upwelling and high surface productivity dominate. Beginning in June-July, as the ITCZ moves north to near the Venezuelan coast, local rainfall reaches a maximum and upwelling diminishes or disappears. The impact of ITCZ motion on local sea surface temperatures (SSTs), rainfall, primary production and Cariaco sediment properties is marked, with varved sediments preserved during anoxic intervals the result of the seasonal contrast between biogenic input during the upwelling season and detrital input from rivers during the wet season. Here we review data from Cariaco Basin and other localities which suggest a coherent climatological response in the tropical Atlantic triggered by a pattern of ITCZ migration that mimicks the seasonal cycle. During periods of cooler North Atlantic SSTs, on time-scales ranging from the Little Ice Age to the Younger Dryas to the cold stadials of the last glacial, evidence suggests a southward shift in the mean latitudinal position of the ITCZ. During warm interstadials and periods of Holocene and deglacial warmth, northward shifts in ITCZ position and its belt of convective rainfall are inferred from increased detrital delivery. The apparent synchronization of changes in Cariaco sediment properties with changes recorded in Greenland ice imply a tight teleconnection between the tropical and high latitudes of the North Atlantic. Whether the rapid shifts in ITCZ position reflect a response to forcing originating in the high latitude Atlantic or to forcing potentially sourced in the tropics is a key question yet to be answered.
DE: 1600 GLOBAL CHANGE (New category)
DE: 1620 Climate dynamics (3309)
DE: 3344 Paleoclimatology
DE: 4267 Paleoceanography
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting