古环境研究室知识库

The timing of orbital-scale Asian monsoon changes, as a direct response of northern summer insolation or remarkably lagged by southern insolation, is still unclear. In particular, various monsoon records obtained in the East Asian monsoon region show distinct phase relationships, indicating additional forcing/feedback mechanisms. Here, monsoon proxies covering the past several precession cycles, either from cave stalagmites or from land/ocean deposits, are first reviewed to present the nearly inverse precipitation responses to the precession forcing between southern and northern East Asia. Modern meteorological observations show that, different modes of tropical Pacific sea surface temperature (SST) could lead to an out-of-phase interannual change in the East Asian summer precipitation. This ENSO influence is also found in the precession scale monsoon variability from the long-term transient modeling, which can explain the phase differences among monsoon proxies. At precession maxima, the East Asian summer monsoon strengthens, causing more precipitation in the north and less precipitation in the south. The SST-precipitation teleconnection is closely associated with a high pressure anomaly due to surface cooling over northwestern Pacific. Therefore, the timing of Asian paleo-monsoon might be significantly influenced by the "internal" ocean feedbacks and one can not expect all the monsoon proxies are consistently responded to the "external" insolation forcing.