Modelling mid-Pliocene climate with COSMOS

C Stepanek,G Lohmann

doi:10.5194/gmd-5-1221-2012

Abstract

Abstract. In this manuscript we describe the experimental procedure employed at the Alfred Wegener Institute in Germany in the preparation of the simulations for the Pliocene Model Intercomparison Project (PlioMIP). We present a description of the utilized Community Earth System Models (COSMOS, version: COSMOS-landveg r2413, 2009) and document the procedures that we applied to transfer the Pliocene Research, Interpretation and Synoptic Mapping (PRISM) Project mid-Pliocene reconstruction into model forcing fields. The model setup and spin-up procedure are described for both the paleo- and preindustrial (PI) time slices of PlioMIP experiments 1 and 2, and general results that depict the performance of our model setup for mid-Pliocene conditions are presented. The mid-Pliocene, as simulated with our COSMOS setup and PRISM boundary conditions, is both warmer and wetter in the global mean than the PI. The globally averaged annual mean surface air temperature in the mid-Pliocene standalone atmosphere (fully coupled atmosphere-ocean) simulation is 17.35 °C (17.82 °C), which implies a warming of 2.23 °C (3.40 °C) relative to the respective PI control simulation.

Highlights

General circulation models of the Earth System provide a suitable tool to understand past climates (e.g. Crowley and North, 1991)
When comparing the mid-Pliocene surface air temperature (SAT) anomalies of experiment 1 and 2 (Fig. 7, 8, 9), we observe for ocean areas in experiment 2 the lack of specific patterns that are present in experiment 1
Since experiment 1 is forced with the SST reconstruction, and since local SST and SAT are closely coupled in ice-free regions, we can conclude that differences in SAT anomaly patterns between both experiments identify regions where our coupled atmosphere-ocean setup is not able to reproduce the mid-Pliocene oceanography as it is interpreted from the geological record

Summary

Introduction

General circulation models of the Earth System provide a suitable tool to understand past climates (e.g. Crowley and North, 1991). Crowley and North, 1991). General circulation models of the Earth System provide a suitable tool to understand past climates They are especially useful since they “can put numbers on ideas” (Ruddiman, 2008). Jansen et al, 2007) Their application allows the investigation of the climate’s reaction to changes in boundary conditions, e.g. of orbital forcing and modifications in the distribution of ice sheets. This topic has been studied for the time slices of the mid-Holocene and the Last Glacial Maximum within the framework of the Paleoclimate Modelling Intercomparison Project (PMIP, e.g. Joussaume and Taylor, 2000). Particular focus is directed at the uncertainties in potential future temperature changes (e.g. Knutti et al, 2008)

Methods

Results

Conclusion