Correlation between oxygen and carbon isotopes of speleothems from Tian’e Cave, central China: Insights into the phase relationship between Asian summer and winter monsoons

Abstract

The correlation of East Asian summer and winter monsoons (EASM and EAWM) is believed to be variable at various timescales and under different climate backgrounds. In order to address this issue, high-resolution δ18O (depleted values indicating a strong EASM) and δ13C records (depleted values representing a weak EAWM) from three stalagmites, covering Marine Isotope Stages (MIS) 4 and 3, are reconstructed from an alpine cave in central China. During MIS 4, millennial-scale changes are clear in δ18O and δ13C records, while the δ13C is only characterized by centennial-scale variability across MIS 3. Changes in these speleothem δ13C records are supported by pollen records from the same area, which suggested millennial-scale alternations between conifer and deciduous broadleaf forests during MIS 4 and a stable C3-type vegetation in MIS 3. After detrended, δ18O changes are positively correlated with the δ13C record at a centennial scale, indicating an anti-phase of EASM and EAWM. In early MIS 4, however, an in-phase relationship of EASM and EAWM can be observed at a millennial scale. Thus, an anti-phased EASM/EAWM can be expected at a centennial scale, while a complicated correlation is seen at a millennial scale. These results imply a variable EASM/EAWM phase relationship under varying climatic conditions through the geological records and at different timescales.