Summer Precipitation Oxygen Isotope in China Monsoon Region over the Last Millennium

Paleoclimate Data Assimilation (PDA) integrates proxy records with climate model simulations to generate spatiotemporally continuous and more accurate reconstructions of past climate fields. However, existing global data assimilation products for China largely rely on tree-ring-based proxy networks, with only minimal inclusion of high-resolution speleothem oxygen isotope (δ¹⁸O) records. To address this gap, this study employs the PHYDA-based data assimilation framework. Building upon the PAGES-2K dataset originally used in PHYDA, we incorporate an additional 20 speleothem δ¹⁸O records from the Chinese monsoon region and combine them with simulations from the iCESM 1.0 model. This approach yields an annually resolved gridded dataset of precipitation δ¹⁸O for the summer months (June–August, JJA) over the period 1000–2000 CE.The dataset has an annual temporal resolution and a spatial resolution of 1.875°×2.5°, covering the geographical domain of 25°–50°N, 70°–125°E. It was generated using MATLAB 2024b and is provided in MAT-file format, containing nine fields including oxygen isotope values, latitude and longitude coordinates, time, and proxy information. The reconstructed δ¹⁸O is validated against modern precipitation observations, drought reconstructions, the IsoGSM-ERA5 δ¹⁸O reconstruction, and six independent speleothem δ¹⁸O records. Results show that the improved data assimilation product exhibits significantly higher correlation with these validation datasets compared to the original PHYDA reconstruction.This dataset provides a spatially continuous, data-assimilated reconstruction of precipitation δ¹⁸O over the past millennium in the Chinese monsoon region. It enables integrated analysis of centennial, decadal, and interannual variability in precipitation δ¹⁸O, facilitates attribution of the respective contributions of temperature and precipitation effects, and offers a new perspective for evaluating isotope-enabled climate models and investigating the spatial heterogeneity of monsoon hydroclimate variability across key periods such as the Medieval Climate Anomaly and the Little Ice Age. Furthermore, it advances comprehensive research that bridges proxy records with climate dynamics modeling.