PALEOCLIMATE: The Last Interglacial

• Main Author: George J. Kukla
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Greenland; Antarc*; Antarctica; Greenland ice core; Greenland Ice core Project; GRIP; ice core; North Atlantic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.624.699; http://jrscience.wcp.muohio.edu/downloads/lastinterglacialscience2000.pdf

The climate of the past 10 millennia, the Holocene, has been portrayed as uniquely benign and stable, with no past equivalent in the Pleistocene. In the core from the Greenland Ice Core Project (GRIP), the temperature proxies of the interval representing the last interglacial, around 125,000 years ago, fluctuate wildly, in striking contrast to the uniform Holocene section of the same core (1). Observations supporting large variability of the last interglacial are reported from around the world. But there are also plentiful arguments to the contrary. Other ice cores in Greenland and Antarctica (2) show little difference in the variability of the Holocene and the older interglacial sections. North Atlantic waters stayed uniformly warm, and temperate flora flourished in interglacial forests in Europe. So who is right? At a symposium held last October at Columbia University (3), s veral questions were asked to resolve the dilemma. Are the geologic records continuous and the sedimentation rates reasonably uniform? Is the interpretation of the climate proxies correct? Most importantly, do the periods ascribed to the last interglacial at different locations refer to the same time interval? And did the last interglacial last as long as the elapsed part of the Holocene? The best information on past global climates comes from deep-sea sediments. Isotopic oxygen ratios in the carbonate shells of bottom dwelling foraminifera document the amount of seawater removed from the oceans and stored as ice on land. Time is divided into episodes with relatively