Ice-age variability from the Vostok deuterium and deuterium excess records

Abstract

The four climatic cycles obtained from the Vostok ice core offer a unique opportunity to study the high-frequency paleoclimatic variability, i.e., on time scales smaller than 15 kyr. We focused our study on the deuterium (δD) and deuterium excess (d) records, which are proxies for local temperature and remote evaporation source temperature and hence give us access to spatial climatic variations. Spectral analyses of paleoclimatic records have shown that the last glacial period (110-15 kyr before present) is characterized by large and fast temperature oscillations. Examples of such variations in the Northern Hemisphere are the so-called Dansgaard-Oeschger oscillations and Heinrich events. At Vostok, these oscillations are also imprinted in the ice, with broadband periodicities between 5 and 8 kyr and between 1.4 and 1.8 kyr. Scenarios for this behavior have recently been developed and argued, as well as connections with the Northern Hemisphere. We now can investigate the stability of the fast spectral features in the previous ice ages recovered in the Vostok isotopic records. This allows us to document the different types of climatic behavior under glacial conditions and hence connect the fast variation statistics with the slower ones controlled by insolation and sea level change. Our results show that δD and d do have a distinct spectral behavior. We discuss the implications on the ocean circulation from such a difference. Copyright 2001 by the American Geophysical Union.