Comparison of North-American pollen-based temperature and global lake-status with Srma AGCM2 output at 6 ka

• Published in: Quaternary science reviews 2004-02, Vol.23 (3-4), p.225-244
• Main Authors: Sawada, M, Viau, A E, Vettoretti, G, Peltier, W R, Gajewski, K
• Format: Article
• Language: English
• Subjects: Freshwater
• ISSN: 0277-3791
• DOI: 10.1016/j.quascirev.2003.08.005

We present new paleoclimate reconstructions for the time period of 6000 yr BP (6 ka) that permit a quantitative comparison to corresponding mapped patterns of the newest version of the Canadian Srma AGCM2 climate model. July temperature reconstructions were estimated using the modern analog technique employing fossil pollen records from the North American Pollen Database. We present a new method of optimizing critical choices within the application of the MAT through modern calibration. The pattern of 6 ka temperature anomalies generated by the Srma AGCM2 generally agree with those of the pollen-based reconstruction, particularly in the presence of a band of positive temperature anomalies across the continent from the Yukon through the Great Lakes region and along the St. Lawrence. This agreement suggests that both the model and data are reconstructing a contraction in the polar vortex over North America at 6 ka. Major areas of disagreement between the pollen-based reconstruction and model simulation are also areas where the data are sparse and edge effects produce less reliable reconstructions. The Srma AGCM2 simulates drier conditions in a west-east band stretching from Alaska through the Canadian prairies and Midwest United States, in agreement with low lake-level observations at 6 ka. Simulated and reconstructed precipitation-evaporation are also in agreement over the southwest United States. With the exception of north central Africa, the Srma AGCM2 fails to capture the northward and eastern extension of the Afro-Asian monsoon belt at 6 ka. General agreement between Srma AGCM2 P-E anomalies and lake status change is found throughout Europe at 6 ka.