Temperature signals of ice core and speleothem isotopic records from Asian monsoon region as indicated by precipitation δ18O

Abstract

Ice cores and speleothem δ18O records from Asia have been widely used as a proxy to reconstruct paleoclimate changes. However, whether those δ18O records are a proxy of temperature or monsoon intensity has remained a great controversy. Generally, ice core δ18O records from non-monsoon and transition regions indicate temperature, but ice core and speleothem δ18O records from monsoon regions have been regarded as proxies for monsoon intensity or precipitation. Here, we address the controversy by showing three 20-yr long daily precipitation δ18O (δ18Op) series and 120 monthly δ18Op series based on 17461 precipitation samples throughout Asia. We find that the δ18Op signals preserved in precipitation are consistent with those in ice cores, both in the non-monsoon and monsoon regions. The results confirm previous research that ice core δ18O records in the non-monsoon region provide reliable histories of surface temperature. However, ice core δ18O records can still directly indicate surface temperature in the monsoon domain if winter/spring precipitation is heavy. When winter/spring precipitation is sparse, inverted ice core records show good agreement with surface temperature records. This may be due to the effect of cloud-top temperatures (which differ from surface temperatures) on summer δ18Op values. Similarly, inverted speleothem δ18O records in the monsoon regions are similar to Greenland/Antarctic ice core δ18O/δD time series and other paleotemperature records. Our findings provide a reinterpretation of Asian ice core and speleothem δ18O records, and demonstrate that temperature signals have been preserved in those archives from the Asian monsoon region.