Mid-Holocene PMIP3/CMIP5 model results: Intercomparison for the South American Monsoon System

The mean precipitation fields for eastern South America from eight mid-Holocene (6 ka) simulations, part of the third phase of Palaeoclimate Modeling Intercomparison Project (PMIP3) and the fifth phase of the Coupled Model Intercomparison Project (CMIP5), are evaluated. These simulations were compared to a new multiproxy compilation of 120 previously published records of changes in South American paleoclimate. Results show that when compared with modern conditions, mid-Holocene proxy data point to a drier Southern Brazil and South Atlantic Convergence Zone (SACZ), but a wetter/similar Northeastern Brazil. This suggests a weaker South American Monsoon System during the mid-Holocene when compared with its modern strength. All analyzed model simulations indicate a similar pattern, with a southward shift of the Intertropical Convergence Zone during the mid-Holocene, related to a weaker South Atlantic subtropical high, and negative annual precipitation anomalies over the SACZ area. Regional differences between the analyzed models were clearly detected.