RADIATION WINDOWS AS INDICATORS OF AN ASTRONOMICAL INFLUENCE ON THE DEVILS HOLE CHRONOLOGY

Abstract

Orbital explanations of paleoclimatic records traditionally focus on daily insolation at ˜ 60°N. We exemplify how insolation at different latitudes and different times of day can explain the timing of the Devil's Hole delta18O record. We combine winter tropical noontime insolation (associated with the source-region for wintertime precipitation) and summer extra-tropical noontime insolation (producing noontime heat to warm terrestrial surfaces). Periods of low winter and high summer insolation are called ``radiation windows'' and yield drier-warmer conditions in the Northern Hemisphere mid-latitudes. When radiation windows are compared with the DH-11 record, the apparent contradiction with Milankovitch (Winograd et al., 1992) may be resolved. The middle-latitude continental climate signal, as recorded by DH-11, tends toward a cooling state until interrupted by a termination. In every instance where the DH-11 record is warming before a radiation window, a termination occurs. If radiation windows occur with antecedent cooling, then there is a complex response of warming with a variable lag effect. Yet, there are no cases where cooling follows a radiation window.