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Strong interannual variation of the Indian summer monsoon in the Late Miocene |
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| Authors: | Hui Tang Jussi T Eronen Arne Micheels Bodo Ahrens |
| Institution: | 1. Department of Geosciences and Geography, University of Helsinki, P.O. Box 64, 00014, Helsinki, Finland 2. Biodiversity and Climate Research Centre (LOEWE BiK-F), Senckenberganlage 25, 60325, Frankfurt am Main, Germany 3. Senckenberg Research Institute and Nature Museum, Senckenberganlage 25, 60325, Frankfurt am Main, Germany 4. Institute for Atmospheric and Environmental Sciences, Goethe University, Altenhoeferallee 1, 60438, Frankfurt am Main, Germany |
| Abstract: | The modern Asian monsoon system exhibits strong interannual variation, which has profound environmental and economical impacts. It has been well-documented that the mean Asian monsoon state underwent significant changes in the Late Miocene (11–5 Ma ago). But how the interannual variability of the monsoon climate evolved during this period is still largely unknown. In this study, a long-term simulation of the Late Miocene with a fully coupled atmosphere–ocean general circulation model (ECHAM5/MPI-OM) at T31L19 resolution is used to explore the interannual variation of the Indian summer monsoon (ISM) in the Late Miocene. The regional climate model COSMO–CLM with a higher spatial resolution (~1° × 1°) is further employed to better characterize the spatial patterns of these variations. Our results show that although the mean ISM circulation is weaker in the Late Miocene runs, its interannual variation is as strong as or even stronger than at present and the dominant periods (~2.6–2.7 years) are shorter than at present (~3.4–8.4 years). It is noticed that while the extratropical influence on the ISM variability is weaker-than-present, a persistent El Niño-Southern Oscillation with stronger-than-present interannual variability is observed in our Late Miocene run. This may have maintained a strong interannual variation of the ISM with a shorter period in the Late Miocene. Our findings do not only improve our understanding of the Asian monsoon evolution in the Late Miocene, but also shed light on the future changes in the interannual variability of the ISM. |
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