07 Dec 2022
07 Dec 2022
Status: this preprint is open for discussion and under review for Climate of the Past (CP).

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

Xin Ren1, Daniel J. Lunt1, Erica Hendy1, Anna von der Heydt2, Ayako Abe-Ouchi3, Bette L. Otto-Bliesner4, Charles J. R. Williams1,5, Christian Stepanek6, Chuncheng Guo7, Deepak Chandan8, Gerrit Lohmann6, Julia C. Tindall9, Linda E. Sohl10,11, Mark A. Chandler10,11, Masa Kageyama12, Michiel L. J. Baatsen2, Ning Tan13,14, Qiong Zhang15, Ran Feng16, Wing-Le Chan3, W. Richard Peltier8, Xiangyu Li17,18,19, Youichi Kamae20, Zhongshi Zhang7,18, and Alan M. Haywood9 Xin Ren et al.
  • 1School of Geographical Sciences, University of Bristol, Bristol, UK
  • 2Institute for Marine and Atmospheric research Utrecht (IMAU), Department of Physics, Utrecht University, Utrecht, the Netherlands
  • 3Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Japan
  • 4Climate and Global Change Dynamics lab, National Center for Atmospheric research, USA
  • 5NCAS, Department of Meteorology, University of Reading, Reading, UK
  • 6Alfred-Wegener-Institut – Helmholtz-Zentrum für Polar and Meeresforschung (AWI), Bremerhaven, Germany
  • 7NORCE Norwegian Research Centre, Bjerknes Centre for Climate Research, Bergen, Norway
  • 8Department of Physics, University of Toronto, Toronto, Canada
  • 9School of Earth and Environment, University of Leeds, Woodhouse Lane, Leeds, West Yorkshire, UK
  • 10Center for Climate Systems Research at Columbia University, New York, NY, USA
  • 11NASA Goddard Institute for Space Studies, New York, NY, USA
  • 12LSCE/IPSL – Laboratoire des Sciences du Climat et de l’Environnement, UMR8212, CEA-CNRS-UVSQ – CE Saclay, L’Orme des Merisiers, Gif-sur-Yvette Cedex, France
  • 13Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
  • 14Laboratoire des Sciences du Climat et de l’Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, Gif-sur-Yvette, France
  • 15Department of Physical Geography and Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden
  • 16Department of Earth Sciences, College of Liberal Arts and Sciences, University of Connecticut, Storrs, USA
  • 17Centre for Severe Weather and Climate and Hydro-geological HazardsWuhan, China
  • 18Department of Atmospheric Science, School of Environmental Studies, China University of Geosciences, Wuhan, China
  • 19Climate Change Research Center, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
  • 20Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan

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: open (until 13 Feb 2023)

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 reply

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).