Pysics of the Ice Age Cycle

Abstract

During the last half of the Pleistocene epoch, beginning roughly 900,000 yrs ago, the variability evidenced in the climate system has been dominated by the 100 kyr ice age cycle first recognized by Broecker and Van Donk (1970). The sequence of events during this time has been markedly improved recently by employing the Milankovitch hypothesis of the origin of ice ages to refine our knowledge of their chronology! Various physical models of this long timescale climate oscillation have been proposed that may be distinguished either as “wet”, in the sense that they rely in large part upon internal forcing due to variation in the strength of the thermohaline circulation (e.g. Broecker and Denton, 1989) or as “dry”, in which case they posit a secondary role for the oceans. Following a brief review of developments in the area of ice age chronology, I will discuss recent and ongoing attempts to resolve the issue as to whether the ice age cycle is primarily a “wet” or a “dry” phenomenon.