Alverson, Keith¹ and Pascal Le Grand²

¹PAGES International Project Office, Bärenplatz 2, 3011 Bern, Switzerland, Tel: +41 31 312 3133, Fax: +41 31 312 3168, E-mail: alverson@pages.unibe.ch, and ²IFREMER, Plausane, France

Glacial/interglacial CO₂ changes from an inverse paleo ocean box model perspective

The main poster presents the IGBP-PAGES program, which seeks to facilitate interdisciplinary and international cooperation in those aspects of paleoenvironmental research most relevant to future concerns.

Alongside this general PAGES presentation, I will present an inverse ocean box modeling study used 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 available 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. 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 in the scenarios listed above, play a secondary role.