Tropical vegetation response to Heinrich Event 1 as simulated with the UVic ESCM and CCSM3

Abstract

Abstract. We investigated changes in tropical climate and vegetation cover associated with abrupt climate change during Heinrich Event 1 (HE1) using two different global climate models: the University of Victoria Earth System-Climate Model (UVic ESCM) and the Community Climate System Model version 3 (CCSM3). Tropical South American and African pollen records suggest that the cooling of the North Atlantic Ocean during HE1 influenced the tropics through a southward shift of the rainbelt. In this study, we simulated the HE1 by applying a freshwater perturbation to the North Atlantic Ocean. The resulting slowdown of the Atlantic Meridional Overturning Circulation was followed by a temperature seesaw between the Northern and Southern Hemispheres, as well as a southward shift of the tropical rainbelt. The shift was more pronounced in the CCSM3 than in the UVic ESCM simulation. Nevertheless, both models suggested a similar response of the vegetation patterns in the tropics around the Atlantic Ocean, where the grass cover increased and the tree cover decreased, specifically in tropical North Africa around 15° N in the UVic ESCM simulation and around 10° N in CCSM3. In the CCSM3 model, the tree and grass cover in tropical Southeast Asia responded to the abrupt climate change during the HE1, which could not be found in the UVic ESCM. The biome distributions derived from both models corroborate findings from pollen records in Southwestern and equatorial Western Africa as well as Northeastern Brazil.