DOI: 10.25921/24fq-1f85
title: NOAA/WDS Paleoclimatology - WAIS Divide Ice Core 67,000 Year Discrete Sample Methane Data

description: The last glacial period exhibited abrupt Dansgaard-Oeschger climatic oscillations, evidence of which is preserved in a variety of Northern Hemisphere palaeoclimate archives. Ice cores show that Antarctica cooled during the warm phases of the Greenland Dansgaard-Oeschger cycle and vice versa, suggesting an interhemispheric redistribution of heat through a mechanism called the bipolar seesaw. Variations in the Atlantic meridional overturning circulation (AMOC) strength are thought to have been important, but much uncertainty remains regarding the dynamics and trigger of these abrupt events. Key information is contained in the relative phasing of hemispheric climate variations, yet the large, poorly constrained difference between gas age and ice age and the relatively low resolution of methane records from Antarctic ice cores have so far precluded methane-based synchronization at the required sub-centennial precision. Here we use a recently drilled high-accumulation Antarctic ice core to show that, on average, abrupt Greenland warming leads the corresponding Antarctic cooling onset by 218 +/- 92 years (2 sigma) for Dansgaard-Oeschger events, including the Bolling event; Greenland cooling leads the corresponding onset of Antarctic warming by 208 +/- 96 years. Our results demonstrate a north-to-south directionality of the abrupt climatic signal, which is propagated to the Southern Hemisphere high latitudes by oceanic rather than atmospheric processes. The similar interpolar phasing of warming and cooling transitions suggests that the transfer time of the climatic signal is independent of the AMOC background state. Our findings confirm a central role for ocean circulation in the bipolar seesaw and provide clear criteria for assessing hypotheses and model simulations of Dansgaard-Oeschger dynamics.
description: Methane concentrations from discrete samples of the WAIS Divide Ice Core measured at Penn State University and Oregon State University.  All depths in meters below the surface.  All methane dry air mixing ratios in nano-mol per mol (ppb) on the NOAA04 scale.  Methane data have been corrected for blank offsets, solubility loss, and gravitational fractionation using interpolated d15N or N2 data reported in WAIS Divide Project Members (2015). Concentrations are slightly (less than 0.5 ppb) different in this file than in previous data reports because of an updated gravitational enrichment correction based on the newest d15N of N2 data.  All ages are given in years before 1950.0 C.E. (A.D.) on the WD2014 timescale.  The Combined WAIS Divide Methane record combines the PSU and OSU data sets, and where they overlap, uses the higher resolution data set.  This combined file is the version of choice for users needing a complete discrete WAIS Divide methane data set.  

WAIS Divide Project Members: Christo Buizert, Betty Adrian, Jinho Ahn, Mary Albert, Richard B. Alley, Daniel Baggenstos, Thomas K. Bauska, Ryan C. Bay, Brian B. Bencivengo, Charles R. Bentley, Edward J. Brook, Nathan J. Chellman, Gary D. Clow, Jihong Cole-Dai, Howard Conway, Eric Cravens, Kurt M. Cuffey, Nelia W. Dunbar, Jon S. Edwards, John M. Fegyveresi, Dave G. Ferris, Joan J. Fitzpatrick, T. J. Fudge, Chris J. Gibson, Vasileios Gkinis, Joshua J. Goetz, Stephanie Gregory, Geoffrey M. Hargreaves, Nels Iverson, Jay A. Johnson, Tyler R. Jones, Michael L. Kalk, Matthew J. Kippenhan, Bess G. Koffman, Karl Kreutz, Tanner W. Kuhl, Donald A. Lebar, James E. Lee, Shaun A. Marcott, Bradley R. Markle, Olivia J. Maselli, Joseph R. McConnell, Kenneth C. McGwire, Logan E. Mitchell, Nicolai B. Mortensen, Peter D. Neff, Kunihiko Nishiizumi, Richard M. Nunn, Anais J. Orsi, Daniel R. Pasteris, Joel B. Pedro, Erin C. Pettit, P. Buford Price, John C. Priscu, Rachael H. Rhodes, Julia L. Rosen, Andrew J. Schauer, Spruce W. Schoenemann, Paul J. Sendelbach, Jeffrey P. Severinghaus, Alexander J. Shturmakov, Michael Sigl, Kristina R. Slawny, Joseph M. Souney, Todd A. Sowers, Matthew K. Spencer, Eric J. Steig, Kendrick C. Taylor, Mark S. Twickler, Bruce H. Vaughn, Donald E. Voigt, Edwin D. Waddington, Kees C. Welten, Anthony W. Wendricks, James W. C. White, Mai Winstrup, Gifford J. Wong and Thomas E. Woodruff