Preprints
https://doi.org/10.5194/cp-2024-8
https://doi.org/10.5194/cp-2024-8
26 Feb 2024
 | 26 Feb 2024
Status: this preprint is currently under review for the journal CP.

South Asian summer monsoon enhanced by the uplift of Iranian Plateau in Middle Miocene

Meng Zuo, Yong Sun, Yan Zhao, Gilles Ramstein, Lin Ding, and Tianjun Zhou

Abstract. The South Asian summer monsoon (SASM) significantly intensified during the Middle Miocene (17–12 Ma), but the driver to this change remains an open question. The uplift of the Himalaya (HM) and Iranian Plateau (IP), and global CO2 variation are prominent factors among suggested drivers. Particularly the impact of high CO2 on the Miocene SASM is little studied despite a large range of reconstructed CO2 values around this period. Here we investigate their effects on the SASM using the fully coupled Ocean-Atmosphere Global Climate Model CESM1.2 through a series of 12 sensitivity experiments. Our simulations show that the IP uplift plays a dominant role in the intensification of the SASM, mainly in the region around northwestern India. The effect of the HM uplift is confined to the range of the HM and its vicinity, producing orographic precipitation change. The topography forcing overall out-competes CO2 variation in driving the intensification of the SASM. In the case of extremely strong CO2 variation, the effects of the two factors are comparable in the core SASM region while in the western region, the topographic forcing is still the dominant driver. A thermodynamical process is proposed to link the uplift of the IP and enhanced SASM through latent heating release. Compared with reconstructions, the response of SASM to the IP uplift is in good agreement with observed precipitation and wind while the effects of the HM uplift and CO2 variation are inadequate to interpret the proxies.

Meng Zuo, Yong Sun, Yan Zhao, Gilles Ramstein, Lin Ding, and Tianjun Zhou

Status: open (until 22 Apr 2024)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2024-8', Anonymous Referee #1, 19 Mar 2024 reply
    • AC1: 'Reply on RC1', yan zhao, 28 Mar 2024 reply
  • RC2: 'Comment on cp-2024-8', Anonymous Referee #2, 19 Mar 2024 reply
    • AC2: 'Reply on RC2', yan zhao, 03 Apr 2024 reply
  • RC3: 'Comment on cp-2024-8', Anonymous Referee #3, 22 Mar 2024 reply
    • AC3: 'Reply on RC3', yan zhao, 06 Apr 2024 reply
Meng Zuo, Yong Sun, Yan Zhao, Gilles Ramstein, Lin Ding, and Tianjun Zhou
Meng Zuo, Yong Sun, Yan Zhao, Gilles Ramstein, Lin Ding, and Tianjun Zhou

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Short summary
Our research explores the intensification of the South Asian summer monsoon (SASM) during the Middle Miocene (17–12 Ma). Using advanced model, we reveal that the uplift of the Iranian Plateau significantly influenced the SASM, especially in northwestern India. This finding surpasses the impact of factors like Himalayan uplift and global CO2 changes. Our study sheds light on the complex dynamics shaping ancient monsoons, providing valuable insights into Earth's climatic history.