Pliocene Model Intercomparison Project Experiment 1: implementation strategy and mid-Pliocene global climatology using GENESIS v3.0 GCM

Abstract

The mid-Pliocene Warm Period (3.29 to 2.97 Ma BP) has been identified as an analogue for the future, with the potential to help understand climate processes in a warmer than modern world. Sets of climate proxies, combined to provide boundary conditions for Global Climate Model (GCM) simulations of the mid-Pliocene, form the basis for the international, data-driven Pliocene Model Intercomparison Project (PlioMIP). Here, we outline the strategy for implementing pre-industrial (modern) and mid-Pliocene forcings and boundary conditions into the GENESIS version 3 GCM, as part of PlioMIP. We describe the prescription of greenhouse gas concentrations and orbital parameters and the implementation of geographic boundary conditions such as land-ice-sea distribution, topography, sea surface temperatures, sea ice extent, vegetation, soils, and ice sheets. We further describe model-specific details including spin-up and integration times. In addition, the global climatology of the mid-Pliocene as simulated by the GENESIS v3 GCM is analyzed and compared to the pre-industrial control simulation. The simulated climate of the mid-Pliocene warm interval is found to differ considerably from pre-industrial. We identify model sensitivity to imposed forcings, and internal feedbacks that collectively affect both local and far-field responses. Our analysis points out the need to assess both the direct impacts of external forcings and the combined effects of indirect, internal feedbacks. This paper provides the basis for assessing model biases within the PlioMIP framework, and will be useful for comparisons with other studies of mid-Pliocene climates.

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