07 Dec 2022
 | 07 Dec 2022

The hydrological cycle and ocean circulation of the Maritime Continent in the mid-Pliocene: results from PlioMIP2

Xin Ren, Daniel J. Lunt, Erica Hendy, Anna von der Heydt, Ayako Abe-Ouchi, Bette L. Otto-Bliesner, Charles J. R. Williams, Christian Stepanek, Chuncheng Guo, Deepak Chandan, Gerrit Lohmann, Julia C. Tindall, Linda E. Sohl, Mark A. Chandler, Masa Kageyama, Michiel L. J. Baatsen, Ning Tan, Qiong Zhang, Ran Feng, Wing-Le Chan, W. Richard Peltier, Xiangyu Li, Youichi Kamae, Zhongshi Zhang, and Alan M. Haywood

Abstract. The Maritime Continent (MC) forms the western boundary of the tropical Pacific Ocean, and relatively small changes in this region can impact the climate locally and remotely. In the mid-Pliocene (from 3.264 to 3.025 million years before present), atmospheric CO2 concentrations were ~ 400 ppm, and the subaerial Sunda and Sahul shelves made the land-sea distribution of the MC different to today. Topographic changes and elevated levels of CO2, combined with other forcings, are therefore expected to have driven a substantial climate signal in the MC region at this time. By using the results from the Pliocene Model Intercomparison Project phase 2 (PlioMIP2) we study the mean climatic features of the MC in the mid-Pliocene and changes in Indonesian Throughflow (ITF) with respect to preindustrial. Results show a warmer and wetter mid-Pliocene climate of the MC and lower sea surface salinity in the surrounding ocean compared with preindustrial. Furthermore, we quantify the volume transfer through the ITF; although the ITF may be expected to be hindered by the subaerial shelves, 10 out of 15 models show an increased volume transport compared with preindustrial.

In order to avoid undue influence from closely-related models that are present in the PlioMIP2 ensemble, we introduce a new metric – the multi-cluster mean (MCM), based on cluster analysis of the individual models. We study the effect that the choice of MCM versus the more traditional analysis of multi-model mean (MMM) and individual models has on the discrepancy between model results and reconstructed proxy data. The clusters reveal spatial signals that are not captured by the MMM, so that the MCM provides us with a new way to explore the results from model ensemble that include similar models.

Xin Ren et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-1281', Anonymous Referee #1, 16 Jan 2023
    • AC1: 'Reply on RC1', Xin Ren, 05 May 2023
  • CC1: 'Comment on egusphere-2022-1281', Tripti Bhattacharya, 13 Feb 2023
    • AC2: 'Reply on CC1', Xin Ren, 05 May 2023
  • RC2: 'Comment on egusphere-2022-1281', Anonymous Referee #2, 02 Apr 2023
    • AC3: 'Reply on RC2', Xin Ren, 05 May 2023

Xin Ren et al.


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Short summary
We investigate the climate of the MC in the mid-Pliocene and find it is warmer and wetter and the sea surface salinity is lower compared with preindustrial. Besides, the fresh and warm water transfer through the MC was stronger in the mid-Pliocene relative to the preindustrial. In order to reduce amplification of model biases in the multimodel results, we introduce a new metric—the multi-cluster mean (MCM), which could reveal spatial signals that are not captured by the multimodel mean (MMM).