Tropical climate and vegetation cover during Heinrich event 1: Simulations with coupled climate vegetation models

• Main Author: Handiani, Dian Noor
• Other Authors: Schulz, Michael, Paul, André, Kucera, Michal
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universität Bremen 2012
• Subjects: Heinrich event 1; tropical climate; vegetation changes; model simulations; data-model comparisons; 550; 550 Earth sciences and geology; ddc:550; Lawrence River; North Atlantic; South Atlantic Ocean
• Online Access: https://media.suub.uni-bremen.de/handle/elib/424; https://nbn-resolving.org/urn:nbn:de:gbv:46-00102922-12

This study focuses on the climate and vegetation responses to abrupt climate change in the Northern Hemisphere during the last glacial period. Two abrupt climate events are explored: the abrupt cooling of the Heinrich event 1 (HE1), followed by the abrupt warming of the Bølling-Allerød interstadial (BA). These two events are simulated by perturbing the freshwater balance of the Atlantic Ocean, with the intention of altering the Atlantic Meridional Overturning Circulation (AMOC) and also of influencing the Intertropical Convergence Zone (ITCZ) and its associated rainbelt. The University of Victoria Earth System-Climate Model (UVic ESCM) is applied in these experiments. The plant-functional types and the temperature from the model output are used for calculating the biome distribution, which is then compared to the available pollen records. In addition, an inter-model comparison for the HE1 is carried out by comparing the UVic ESCM with the Community Climate System Model version 3 (CCSM3). In the UVic ESCM, the HE1 climate is imitated by adding freshwater to the St. Lawrence River where it runs into the North Atlantic Ocean, which causes a slowdown of the AMOC. The weakening of the AMOC is followed by a cooler climate in the North Atlantic Ocean and a warmer climate in the South Atlantic Ocean. This surface temperature see-saw between the Northern and Southern Hemispheres causes a southward shift of the tropical rainbelt. The simulated drier climate north of the Equator during the HE1 event causes an increase of desertification and the retreat of broadleaf forests in West Africa and northern South America. On one hand, the model results for the HE1 event can be shown to be in agreement with the pollen records from tropical Africa and northern South America. On the other hand, the model fails to predict savannah and grassland in western tropical South America. In addition, the model predicts similar biome distributions for the pre-industrial as well as the last glacial climate, except in tropical northern Africa ...