Dr. Frédéric JACQUES, Young International Scientist from Nanjing Institute of Geology and Palaeontology Chinese Academy of Sciences (NIGPAS), and collaborators developed a new model for palaeoclimate reconstruction of the monsoon regions of China recently.
Our understanding of past climatic changes depends on our ability to obtain reliable palaeoclimate reconstructions. Climate Leaf Analysis Multivariate Program (CLAMP) uses the physiognomy of woody dicot leaf assemblages to quantitatively reconstruct terrestrial palaeoclimates. The present calibrations include sites from North America, Japan and Pacific islands, but lack Chinese data. As a result, palaeoclimatic reconstructions based of Chinese fossil leaf assemblages tend to be wrong, with very high precipitation. Dr. Frédéric Jacquesand Prof. WANG Weiming from NIGPAS, Mr. HUANG Yongjiang, Drs. SU Tao, XING Yaowu, Prof. ZHOU Zhekun from Kunming Institute of Botany, CAS, and Robert Spicer from the Open University established a new CLAMP calibration that actually reflects Chinese monsoon climate through the inclusion of 45 Chinese sites to the database. The study demonstrates that the new model has a good accuracy for the reconstruction of Chinese and South-East Asia monsoon climates and that such a model is reliable for the reconstruction of Chinese palaeoclimates during the Neogene. This new calibration has already been accepted by the international scientific community and is already used for related research. These results have been published in a recent issue of the international journal Global and Planetary Change.
The new monsoonal calibration was tested using a cross validation procedure to show it really improves the accuracy of the palaeoclimatic reconstruction for Chinese sites, especially for the moisture related parameters. The mean absolute error for Growing Season Precipitation (GSP) of the Chinese sites is 294.6 mm in the new monsoonal calibration whereas it was 1609.6 mm in the old calibration. Results for the three wettest months and three driest months are also more accurate and precise, which allows us to study seasonality of the precipitation, and hence the monsoon. The new monsoonal calibration also gives accurate results for enthalpy reconstruction. Enthalpy is a parameter that is used for palaeoaltimetry, the new calibration is therefore useful for studies of land surface height changes in China, height changes which in turn can affect the strength of the monsoon. The new monsoonal calibration was tested on two fossil sites from the Late Miocene of southwestern China, namely the Lincang and Xiaolongtan palaeofloras. A comparison of results from the new monsoonal calibration and the Physg3brcAZ calibration shows that there is no strong difference in temperature estimates for the two calibrations, but there is a strong difference in the moisture related parameters. The use of this new monsoonal calibration is recommended for palaeoclimate reconstructions in China.
Paper reference: Frédéric M.B. Jacques, Tao Su, Robert A. Spicer, Yaowu Xing, Yongjiang Huang, Weiming Wang, Zhekun Zhou. 2011. Leaf physiognomy and climates: are monsoon systems different? Global and Planetary Change 76 (1-2): 56-62.
Figure caption: The colour gradient on the left refers to GSP. Chinese sites (circles) group away from the 3b sites (squares), even those with high GSP scores (in blue).
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