PAGES-CHANGES LINKAGES AND SOME THOUGHTS ON GLACIAL/INTERGLACIAL CHANGES IN ATMOPSHERIC CO2 CONCENTRATION

The primary goal of this talk is to present the IGBP-PAGES program, Past Global Changes, which seeks to facilitate interdisciplinary and international cooperation in those aspects of paleoenvironmental research most relevant to future concerns. I will draw particular attention to activities within PAGES concerned with carbon, hydrology and global environmental systems on glacial/interglacial timescales and will seek feedback from the CHANGES community on how to better incorporate the relatively neglected archives continental shelves, karst and drylands within PAGES.

In addition, I will present an inverse ocean box modeling effort to address the question of what may have caused decreased atmospheric CO2 concentration during glacial periods. The inverse procedure seeks solutions that are consistent, within prescribed uncertainties, with both applied paleodata constraints and box model conservation equations while relaxing traditional assumptions such as exact steady state and precise prescription of uncertain model parameters. Decreased ventilation of Southern Ocean deep water, decreased Southern Ocean air-sea gas exchange, and enhanced high latitude biological pumping are all shown to be individually capable of explaining available paleodata constraints provided that significant calcium carbonate compensation is allowed. The role of increased solubility of CO2 associated with cooling of low and mid latitude surface waters plays only a minor contributing role in these scenarios scenarios. However, we further show exact solutions to the 7-box ocean carbon cycle model, found using the inverse procedure, which indicate that low and mid latitude sea surface temperature changes could have served as the primary driver of atmospheric CO2 variability on glacial-interglacial timescales. The most substantial difference between glacial and interglacial climates is, after all, temperature. In this hypothesis, additional systematic feedbacks, such as those which have been suggested as possible primary mechanisms the scenarios listed above, play a secondary role.