PARENT SESSION
Poster Session 5: Climate Dynamics
Tuesday, August 9, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Post glacial climate change in the Midwestern USA from 13C in oak wood.
Guyette, Richard*,, Stambaugh, Michael, Muzika, Rose-Marie, Dey, Daniel,
ABSTRACT- The last postglacial climate epoch was marked by abrupt climate change and cooling events such as the Younger Dryas. This climate epoch is well documented in marine and maritime environments but much less is known of this epoch in continental climates that are now important in agricultural regions. Oak trees recruited, buried and excavated by streams and sediments in Missouri and Iowa, USA, provide a climate proxy. We use 189 14C dated and tree ring dated oak trees to develop a 14,000 year long chronology of 
13C in oak wood. The chronology is tested and adjusted for 13C trends as wood ages and loses density. Values of 13C in oak wood are found to be positively and significantly correlated with 18O from Greenland ice cores. The termination of the Younger Dryas in mid-continental North America is marked by a predicted and abrupt increase in the climate sensitive stable isotope 13C. This change is found to be synchronous with dates of Younger Dryas termination based on studies from marine and maritime regions of the North Atlantic. Other climate perturbations in the North Atlantic region, such as the Younger Dryas II are also inferred to have been synchronous with changes in mid-continental climate. During the Younger Dyras, an increase in 13C about 11,800 cal yrs BP is coincident with intra Younger Dryas variability as documented by sediment core data. The post Younger Dryas transition to Holocene climate is found to be consistent with changes in 18O from ice core data. Our results from 13C in individual oak trees indicate that climate changes in mid-continental North America were abrupt and generally synchronous with those in the North Atlantic Region.
Key words: paleoclimate, Quercus, stable isotope, Midwest