PARENT SESSION
Symposium #26: Gasping for CO2: Ecological Effects of Past Variations in Atmospheric CO2.
Organized by: JW Williams and S Cowling
Thursday, August 8. 9:00 AM to 11:30 AM. Turquoise Ballroom, TCC.
CO2 -climate-vegetation interactions at the LGM as simulated by a coupled climate-vegetation model.
LEVIS, SAMUEL*,1, 1 NATIONAL CENTER FOR ATMOSPHERIC RESEARCH, BOULDER, CO
ABSTRACT- The synchronously coupled GENESIS-IBIS model was used to simulate climate-vegetation interactions with Last Glacial Maximum (LGM) boundary conditions, corresponding to approximately 21000 years before present. From the simulations performed, two positive feedbacks stand out: (1) A springtime middle to high latitude positive feedback. With colder temperatures, forests give way to highly reflective snow covered tundra and polar desert, thus enhancing the cooling trend. The same feedback in reverse operates in a GENESIS-IBIS doubled CO2 global warming simulation. In both cases, the vegetation responds mainly to the temperature change. The physiological response of vegetation to the higher or lower CO2 plays a secondary role in enhancing this feedback. (2) A tropical positive feedback, according to which climate-induced aridity leads to reduced forest cover which leads to enhanced aridity. This hydrological feedback is greatly enhanced by the physiological response of trees to lower CO2.
KEY WORDS: CO2, climate, vegetation, model