Evaluation of PMIP2 and PMIP3 simulations of mid-Holocene climate in the Indo-Pacific, Australasian and Southern Ocean regions

• Main Authors: Ackerley, D., Reeves, J., Barr, C., Bostock, H., Fitzsimmons, K., Fletcher, M., Gouramanis, C., McGregor, H., Mooney, S., Phipps, S., Tibby, J., Tyler, J.
• Format: Report
• Language: English
• Published: 2017
• Subjects: Pacific; Southern Ocean; ice core
• Online Access: http://hdl.handle.net/11858/00-001M-0000-002E-34CF-9

Paleoclimate proxy reconstruction initiatives, such as the Australian component of the international paleoclimate synthesis effort: INTegration of Ice core, MArine and Terrestrial records (OZ-INTIMATE), are important as they provide evidence of past climatic conditions that are necessary to evaluate global General Circulation Models (GCMs). One of the key outputs from the OZ-INTIMATE project was the production of spatially-coherent, climatic reconstructions over the southern Maritime Continent, Australasia and the Southern Ocean. The OZ-INTIMATE results were presented as regional, "simplified patterns of temperature and effective precipitation" and those regions spanned a large enough area to contain several GCM grid boxes. Therefore, the "upscaling" of individual reconstructions (through OZ-INTIMATE) to a scale that was resolved by GCMs, presented an ideal opportunity for a direct comparison. This study uses the same "simplified patterns of temperature and effective precipitation" approach from OZ-INTIMATE on data from an ensemble of GCMs. The GCM data are taken from the Paleoclimate Modeling Intercomparison Project (PMIP) mid-Holocene (6000 years before present, 6 ka) and pre-industrial control (c1750 C.E., 0 ka) experiments. The synthesis presented here shows that, on the whole, the models and proxies agree on the differences in climate state for 6 ka relative to 0 ka, when they are insolation driven. The main disagreement between the models and proxies occurs over the Tropical West Pacific warm pool and arises from an intensification of an existing error (the "cold tongue bias"). This study also presents a mechanism whereby the strength of the Southern Hemisphere, mid-latitude westerly wind strength reduces but rainfall increases over the southern temperate zone of Australia. Such a mechanism may be useful for resolving disparities between different regional proxy records, and model simulations. Finally, after assessing the available datasets (model and proxy), opportunities for better model-proxy integrated ...