In a study published in
npj Climate and Atmospheric Science, a joint research group from the Institute of Earth Environment of the Chinese Academy of Sciences, the Stockholm University, and the California State University found that while land recycled water vapor contributed more than 60% to precipitation in northern China, the precipitation δ
18O (δ
18O
p) was primarily influenced by the relative oceanic moisture contribution.
For decades, precipitation δ18O (δ18Op) has been a crucial proxy in reconstructing past climate changes. However, its interpretation, especially under the influence of the East Asian summer monsoon (EASM), has been contentious. In northern China, located at the margin of the EASM region, the more continental climate raises questions about the impact of varying moisture sources on δ18Op.
To delve into the complexities of moisture source variability and their impact on δ18Op, the researchers employed a general circulation model (CAM3), enhanced with water-tagging and stable water isotopes modules, to quantitatively trace water vapor from its source to northern China. 、
They found that over 60% of precipitation in northern China originated from local recycled moisture and other terrestrial water vapor. However, this substantial contribution had a minimal effect on δ18Op values, suggesting a predominant transpiration over evaporation.
They suggested that despite the high percentage of terrestrial moisture, the δ18Op was predominantly affected by oceanic moisture sources, with the Pacific Ocean (24.4%) and the North Indian Ocean (13.0%) being crucial contributors.
In addition, the researchers underscored the role of Pacific Decadal Oscillation in modulating δ18Op through altering Pacific Ocean and North Indian Ocean moisture contributions. Interestingly, local precipitation patterns display an inverse phase variation with δ18Op, emphasizing the complex dynamics between local moisture recycling and large-scale oceanic influences.
These insights are valuable in understanding past climate variability, offering a new lens through which to view the complex climatic systems of monsoonal China.
Contact: BAI Jie, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, China. Email: baijie@ieecas.cn