Wet periods in northeastern Brazil over the past 210 kyr linked to distant climate anomalies.
The tropics are the main source of the atmosphere's sensible and latent heat, and water vapour, and are therefore important for reconstructions of past climate. But long, accurately dated records of southern tropical palaeoclimate, which would allow the establishment of climatic connections to distant regions, have not been available. Here we present a 210,000-year (210-kyr) record of wet periods in tropical northeastern Brazil--a region that is currently semi-arid. The record is obtained from speleothems and travertine deposits that are accurately dated using the U/Th method. We find wet periods that are synchronous with periods of weak East Asian summer monsoons, cold periods in Greenland, Heinrich events in the North Atlantic and periods of decreased river runoff to the Cariaco basin. We infer that the wet periods may be explained with a southward displacement of the Intertropical Convergence Zone. This widespread synchroneity of climate anomalies suggests a relatively rapid global reorganization of the ocean-atmosphere system. We conclude that the wet periods probably affected rainforest distribution, as plant fossils show that forest expansion occurred during these intermittent wet intervals, and opened a forest corridor between the Amazonian and Atlantic rainforests.
Wang
Xianfeng
X
Department of Geology & Geophysics, University of Minnesota, Minneapolis, Minnesota 55455, USA. wang0452@umn.edu
Auler
Augusto S
AS
Edwards
R Lawrence
RL
Cheng
Hai
H
Cristalli
Patricia S
PS
Smart
Peter L
PL
Richards
David A
DA
Shen
Chuan-Chou
CC
D001272:Atmosphere; D044822:Biodiversity; D001938:Brazil; D005580:Fossils; D049690:History, Ancient; D009792:Oceans and Seas; D011891:Rain; D012621:Seasons; D013696:Temperature; D014197:Trees / Q000502:physiology; D014329:Tropical Climate; D014872:Water Movements; D014887:Weather; D014919:Wind