How air bubbles trapped in glacial ice have changed our view of abrupt climate change

Jeff Severinghaus

Professor of Geosciences
Scripps Institution of Oceanography
University of California, San Diego

Water isotopes from Greenland ice cores have suggested that abrupt (decade-scale) climate change is a characteristic and recurring feature of the Earth system. However, doubts about the magnitude and geographical extent of these events persist, because water isotopes (O^-18 and deuterium) are affected by factors other than temperature, such as seasonality of precipitation and vapor source conditions. Recent measurements of the isotopes of argon and nitrogen gas trapped in air bubbles in glacial ice have confirmed the reality of the abrupt temperature shifts, showing that they typically have magnitudes of 10oC over several decades or less. Synchronous shifts in atmospheric methane concentrations reconstructed from measurements of the trapped air further imply that the abrupt changes were geographically widespread, because methane sources (dominantly wetlands) are widely distributed over the globe. Taken together with abundant paleoclimatic records from low and high latitudes, the data suggest a view of abrupt climate change as involving the entire northern hemisphere, with large and sudden terrestrial hydrological changes in low latitudes. Low latitude temperature changes were small or unknown, with minimal involvement of the southern hemisphere (or possibly an antiphased response). The implied shifts in hydrology serve as a warning that future abrupt climate change may stress human societies and ecosystems more through rainfall changes than through temperature.

About the Lecturer

http://icebubbles.ucsd.edu/

Jeff Severinghaus