PARENT SESSION
Symposium #7: Long-term perspectives on ecological questions: A symposium in tribute to Margaret Davis.
Sponsored by ESA Paleoecology Section
Organized by: L.B. Brubaker, V. Card, and L.J. Graumlich.
Tuesday, August 7, 2001. 8:00 AM to 12:00 PM. Lecture Hall
Biosphere-climate interactions and global palaeoecology.
Harrison, Sandy1, Kohfeld, Karen1, LeQuere, Corinne1, Tegen, Ina1, Prentice, Iain Colin1, 1
ABSTRACT- Palaeorecords of atmospheric composition and marine and terrestrial ecosystems during the glacial-interglacial-cycles offer a glimpse of the Earth as a tightly coupled physical, chemical and biological system. A deductive data-model comparison approach is providing especial insight into the role of terrestrial and marine ecosystems as active participants in climate change. For example, it is now well established that vegetation-albedo feedback was key to the major land-surface changes that took place in northern Africa after 6000 years BP. This finding relied on juxtaposing physically based models with ecosystem information from pollen and plant macrofossils. A more complex example involves the role of aeolian dust. Based on models of climate, ecosystems, dust deflation and transport, compared to palaerodata on lakes, ecosystems and aeolian fluxes to the land and ocean, it is hypothesized that atmospheric CO2 concentration, tropical sea-surface temperature and tropical atmospheric dust content are linked by mutually reinforcing feedbacks that contribute to the existsence of discrete, metastable "glacial" and "interglacial" climate modes. Proposed mechanisms include the effects of low CO 2 concentrations and low sea-surface evaporation on terrestrial vegetation density, which partly controls dust deflation, and the effect of high dust loadings on marine export production, which partly controls atmospheric CO 2.
KEY WORDS: dust, albedo, CO2, paleoclimate