1. Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island 02882, USA
2. Geosciences Department, Pennsylvania State University, University Park, Pennsylvania 16802, USA
3. Departments of Geology and Environmental Science, Washington State University, Vancouver, Washington 98686, USA
4. Present address: Department of Geosciences, Princeton University, Princeton, New Jersey 08544, USA.

Correspondence to: Jeffrey P. Severinghaus¹ Correspondence and requests for materials should be addressed to J.P.S. (e-mail: Email: jeffs@gsosun1.gso.uri.edu.)

Abstract

Rapid temperature change fractionates gas isotopes in unconsolidated snow, producing a signal that is preserved in trapped air bubbles as the snow forms ice. The fractionation of nitrogen and argon isotopes at the end of the Younger Dryas cold interval, recorded in Greenland ice, demonstrates that warming at this time was abrupt. This warming coincides with the onset of a prominent rise in atmospheric methane concentration, indicating that the climate change was synchronous (within a few decades) over a region of at least hemispheric extent, and providing constraints on previously proposed mechanisms of climate change at this time. The depth of the nitrogen-isotope signal relative to the depth of the climate change recorded in the ice matrix indicates that, during the Younger Dryas, the summit of Greenland was 15 3 °C colder than today.