Changes in CO2 concentration and carbon cycle during the last glacial termination

Abstract:

 Ice cores from Antarctica have revealed that atmospheric CO₂ concentration is strongly linked with climate over the past hundreds of thousands years. During the last glacial termination CO₂ concentration increased by ~80 ppm and the increase rate changed with abrupt climate events such as Bølling-Allerød and Younger Dryas. Precise and high-resolution CO₂ records during the events may help us better understand climate-carbon cycle feedbacks. However, most of the existing ice core records are severely smoothed by gradual bubble close-off and gas diffusion in the firn layer. Recently, a CO₂ record with an unprecedented temporal resolution was obtained from West Antarctic Ice Sheet (WAIS) Divide ice core, where glaciological conditions permit a relatively small gas smoothing effect. The WAIS Divide record shows three abrupt CO₂ increases of 10-15 ppm in less than 200 years during the last glacial termination. The ancient air extracted from the WAIS Divide ice core was in a form of air hydrates and the results must yet be confirmed with other ice cores. Here we present a new high-resolution atmospheric CO₂ record from the Siple Dome ice core, in which air is preserved only in bubbles. Our data cover 11.0-21.0 ka with an average time resolution of 65 yrs. The Siple Dome records show that abrupt CO₂ increases of ~ 10 ppm within 100-200 years at 11.7, 14.7, and 16.3 ka, confirming the rapid CO₂ increases observed in the WAIS Divide record. We are analyzing the common and uncommon features during the three rapid CO₂ increases in order to decipher the control mechanisms. The updated results will be presented at the meeting.