Modelling carbon cycle feedbacks during abrupt climate change

Abstract

Past climate, both before and after the Last Glacial Maximum, was marked by a series of abrupt transitions from cold to warm states associated with significant changes in atmospheric CO 2. Mechanisms which led to these transitions most likely include variability in the thermohaline circulation (THC) as inferred from deep sea sediment records. In this study, we investigate the changes in atmospheric CO 2 concentration that arise during abrupt climate change events. This is accomplished through our use of meltwater pulse scenarios applied to an ocean–atmosphere–sea ice model coupled to an inorganic carbon component. We perform transient simulations with increased freshwater discharge to high latitude regions in both hemispheres from a glacial equilibrium climate to simulate meltwater episodes. We find that changes in ocean circulation and carbon solubility lead to significant increases in atmospheric CO 2 concentrations when we simulate meltwater episodes in both hemispheres. The magnitude of increase in atmospheric CO 2 is between 10 and 40 ppmv , which accounts for some of the changes in CO 2 as recorded in the ice core records.