Articles | Volume 12, issue 8
Clim. Past, 12, 1619–1634, 2016

Special issue: PlioMIP Phase 2: experimental design, implementation and scientific...

Clim. Past, 12, 1619–1634, 2016

Research article 08 Aug 2016

Research article | 08 Aug 2016

Sensitivity of Pliocene climate simulations in MRI-CGCM2.3 to respective boundary conditions

Youichi Kamae1,2, Kohei Yoshida3, and Hiroaki Ueda1 Youichi Kamae et al.
  • 1Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, 305-8572, Japan
  • 2Scripps Institution of Oceanography, University of California San Diego, La Jolla, 92093-0206, USA
  • 3Meteorological Research Institute, Tsukuba, 305-0052, Japan

Abstract. Accumulations of global proxy data are essential steps for improving reliability of climate model simulations for the Pliocene warming climate. In the Pliocene Model Intercomparison Project phase 2 (PlioMIP2), a part project of the Paleoclimate Modelling Intercomparison Project phase 4, boundary forcing data have been updated from the PlioMIP phase 1 due to recent advances in understanding of oceanic, terrestrial and cryospheric aspects of the Pliocene palaeoenvironment. In this study, sensitivities of Pliocene climate simulations to the newly archived boundary conditions are evaluated by a set of simulations using an atmosphere–ocean coupled general circulation model, MRI-CGCM2.3. The simulated Pliocene climate is warmer than pre-industrial conditions for 2.4 °C in global mean, corresponding to 0.6 °C warmer than the PlioMIP1 simulation by the identical climate model. Revised orography, lakes, and shrunk ice sheets compared with the PlioMIP1 lead to local and remote influences including snow and sea ice albedo feedback, and poleward heat transport due to the atmosphere and ocean that result in additional warming over middle and high latitudes. The amplified higher-latitude warming is supported qualitatively by the proxy evidences, but is still underestimated quantitatively. Physical processes responsible for the global and regional climate changes should be further addressed in future studies under systematic intermodel and data–model comparison frameworks.

Short summary
Climate model simulations conducted in previous studies tended to underestimate the late-Pliocene higher-latitude warming suggested by proxy evidences. We explore how prescribed trace gases, ice sheets, vegetation, lakes and orography affect the Pliocene climate simulation based on a protocol of the PlioMIP Phase 2. The revised boundary forcing data lead to amplified higher-latitude warming that is qualitatively consistent with the paleoenvironment reconstructions.