GFI/BCCR Seminar: The new WAIS Divide (Antarctic) ice core: new constraints on the physics of the 'bipolar seesaw'

Eric Steig (Department of Earth and Space Sciences, University of Washington, US):

The new WAIS Divide (Antarctic) ice core: new constraints on the physics of the 'bipolar seesaw'

Abstract
The West Antarctic Ice Sheet (WAIS) Divide ice core project was designed to obtain a record of past climate that rivals those from central Greenland (GISP2, GRIP, etc.). The project has been a success: WAIS Divide is the highest-resolution deep ice core ever obtained outside Greenland, with annual resolution all the way to the bed at 3404 meters and 68000 years old. The record reveals significant new information about millennial timescale variability.

First, the WAIS Divide shows earlier warming at the end of the last ice age, more in line with Milankovitch theory than do other Antarctic ice core records. Second, the precise dating of the core shows that the peaks in the millennial-scale variations in oxygen isotopes known as Antarctic Isotope Maximum (AIM) events lag the abrupt warmings of the Dansgaard-Oeschger events by 200 years. Yet, third, isotope data also shows definitive evidence for shifts in atmospheric circulation around Antarctica, in phase with the D-O events. Thus, there is evidence for both the slow oceanic teleconnection and fast atmospheric teleconnections suggested by previous theoretical and modeling studies to explain millennial-scale variability in the Northern and Southern Hemispheres.