Coupled Effects of Moisture Transport Pathway and Convection on Stable Isotopes in Precipitation across the East Asian Monsoon Region: Implications for Paleoclimate Reconstruction

This study investigated the variations in stable oxygen isotopes in daily precipitation (δ18Op) collected between 2010 and 2013 at four sites across the East Asian monsoon region to address the controversy whether local meteorological factors, moisture transport pathway or convection dominates the δ18Op changes. We found that the δ18Op time series exhibit opposite seasonal patterns between the southern and northern sites; however, relatively low δ18Op values occur at each site during summer. The opposite seasonal patterns are closely related to the proportional change in the contributions from oceanic (> 52% in the south) and continental (> 85% in the north) moisture sources. Moisture transport distances also influence the seasonal δ18Op fluctuations. In the south, the moisture transported over short distances from the middle of the western Pacific Ocean results in relatively high δ18Op values during the pre-monsoon season. In contrast, long-distance transport of moisture from the Indian and Equatorial Pacific Oceans during the monsoon season results in relatively low δ18Op values. In the north, relatively low δ18Op values during the monsoon season can be attributed to an increase in relatively distant moisture originated from the middle of the western Pacific Ocean. Convection only plays a role in affecting δ18Op values in the south during the monsoon season. Our study suggests that moisture transport pathway (moisture sources and moisture transport distances) is a major factor that governs seasonal variations in δ18Op across the East Asian monsoon region, which has implications for the interpretation of paleoclimate records from this region.