GEOGRAPHY

Xi’an Jiaotong University is making progress in using stalagmite records to reconstruct the Holocene climate change


Stalagmite carbonate oxygen isotope records have long been thought to reflect changes in precipitation in monsoon regions, further reflecting monsoon intensity. However, this understanding has been controversial, and in the Arabian Sea region, the marine record, which is also thought to reflect the changes in the Indian monsoon, is significantly different from the terrestrial record represented by stalagmite oxygen isotopes in terms of precession cycle, which is called the “sea-land precession phase confusion”. What kind of records can truly reflect monsoon changes? How did the climate of the Holocene Arabian Sea region change and the Indian monsoon? The answers to these questions are not clear.

In response to the above problems, the Institute of Global Environmental Change of Xi’an Jiaotong University used Qunf cave stalagmites in southern Oman to carry out multi-index record research including carbonate oxygen isotopes, including uranium content, carbon isotopes, trioxygen isotopes, fluid inclusions, trace elements, etc., and combined with EC-Earth climate simulation experiments to reconstruct the Holocene climate change and Indian monsoon change characteristics in southern Oman. It is found that in the early and middle Holocene period, in addition to the Indian summer wind, the North African summer wind also had a non-negligible impact on the study area, and the enhanced North African summer wind brought distant water vapor, which together with the near-source water vapor carried by the Indian summer wind had an impact on precipitation in southern Oman. The North African monsoon and the Asian monsoon to which the Indian monsoon belongs are jointly affected by solar radiation in the northern hemisphere on the precession cycle, so the North African monsoon and the Asian monsoon can be regarded as a “super monsoon” whole, that is, the North Africa-Asian monsoon. Therefore, the stalagmite carbonate oxygen isotopes in Qunf Cave do not reflect the amount of monsoon precipitation as previously recognized, but reflect the changes in water vapor sources generated by large-scale circulation.

EC-Earth climate simulations of 8,000-year-old and modern climate differences.

At the same time, the multi-indicator records of Qunf cave stalagmites reflect that the study area underwent a transition from drought to wetness during the Holocene stage, which was confirmed by climate simulation experiments, which is different from previous understanding, and provides a new reference for the study of this area. The study also pointed out that the ocean upwelling record in the Arabian Sea does not reflect the change in the intensity of the Indian summer wind, and the inconsistency between the land stalagmite oxygen isotope record and the marine record around the Arabian Sea is not opposite, but the two depict different aspects of the same North Africa-Asia monsoon dynamic system.

The study was published in Nature Communications. (All photos courtesy of Xi’an Jiaotong University)

The work was published in Nature Communications under the title “Stalagmite Multi-Indicator Records and Climate Simulations Reconstructing Holocene Climate Change in Southern Oman”. The first author of the article is Tian Ye, a doctoral candidate at the Institute of Global Environmental Change of Xi’an Jiaotong University, and Professor Cheng Hai of the Institute of Global Environmental Change of Xi’an Jiaotong University is the corresponding author. (Source: Yan Tao, China Science News)

Related paper information:https://doi.org/10.1038/s41467-023-40454-z



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