Glacial evolution of the plio-pleistocene: Role of continental and arctic ocean ice sheets

Abstract

An empirical method is developed for assessing long-term trends in the growth of both mid-latitude Northern Hemisphere continental and high-latitude Arctic Ocean ice sheets during the last 5 million years. The growth of Arctic Ocean Ice Sheets is assumed to be modulated principally by caloric insolation variations related to obliquity, while variations in the extent of Northern Hemisphere continental ice sheets are controlled by precession-dominated caloric insolation variations. In developing empirical equations for the tendency of Arctic Ocean Ice Sheet growth ( A) and the tendency for continental ice sheet growth ( C), we have also assumed that there would be strong feedback effects between the two ice masses contingent upon North Atlantic surface water heat transport. A clear correspondence between high A values and cold paleotemperatures recorded in North Atlantic deep-sea cores spanning the last 2.0 m.y. is taken as evidence of a long-term linkage with the North Atlantic. Alternatively, strong similarities were found to exist between the predicted record of C and the classical terrestrial glacial/interglacial record back to about 3.2 m.y. B.P. A marked coincidence was also found between the combined tendency of continental and Arctic Ocean Ice Sheet growth ( A + C) with the deep-sea δ 18O record. A dramatic increase in the amplitude and period of δ 18O variations beginning at about 1.0 m.y. B.P. is reflected by a sharp increase in the number of A + C values greater than the long-term mean. Phase relationships between the earth's orbital parameters and North Atlantic sea surface temperatures have apparently played a major role in the terrestrial and marine glacioclimatic records for at least the last 3.2 million years.