Interhemispheric anti-phasing of rainfall during the last glacial period |
| |
| Authors: | Xianfeng Wang Augusto S Auler R Lawrence Edwards Hai Cheng Emi Ito Maniko Solheid |
| |
| Institution: | aDepartment of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455, USA;bCPMTC, Instituto de Geociências, Universidade Federal de Minas Gerais, Av. Antonio Carlos 6627, Belo Horizonte, Minas Gerais 31270-901, Brazil |
| |
| Abstract: | We have obtained a high-resolution oxygen isotopic record of cave calcite from Caverna Botuverá (27°13′S, 49°09′W), southern Brazil, which covers most of the last 36 thousand years (ka), with an average resolution of a few to several decades. The chronology was determined with 46 U/Th ages from two stalagmites. Tests for equilibrium conditions show that oxygen isotopic variations are primarily caused by climate change. We interpret our record in terms of meteoric precipitation changes, hence the variability of South American Monsoon (SAM) intensity. The oxygen isotopic profile broadly follows local insolation changes and shows clear millennial-scale variations during the last glacial period with amplitudes as large as 3‰ but with smaller centennial-scale shifts (<1‰) during the Holocene. The overall record is strikingly similar to, but strongly anti-correlated with, a number of records from the Northern Hemisphere.We compared our record to other precisely dated contemporaneous records from Hulu Cave eastern China. Minima in δ18O (wet periods, intense SAM) at our site are synchronous with maxima in δ18O (dry periods, weak East Asian Monsoon, EAM) in eastern China (within precise dating errors) and vice versa. This anti-phased precipitation relationship between two low-latitude locations may be interhemispheric in extent, based on comparison with records from other sites. Precipitation anti-phasing may be related to north–south shifts in the mean position of the intertropical convergence zone (ITCZ) and asymmetry in Hadley circulation in two hemispheres, associated not with seasonal changes as observed today, but with millennial-scale climate shifts. The millennial-scale atmospheric see-saw patterns that we observe could have important controls and feedbacks on climate within hemispheres because of water vapor's greenhouse properties. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
