Surface Albedo Increase following Massive Pleistocene Explosive Eruptions in Western North America

Abstract

The eight massive Pleistocene explosive volcanic eruptions which occurred in western North America produced rhyolitic ash layers estimated to have covered from 0.38 to 2.76 × 10⁶ km² of the western and central portions of the continent. The surface albedo increases in the Northern Hemisphere resulting from these light-colored ash covers varied from around 0.06 to 0.41% assuming ash albedos based on color of around 53 to 65%. These albedo increases resulted in hemispheric temperature decreases of from around 0.07° to 0.41°C with greater cooling in and adjacent to the ash-covered regions. Such albedo-induced temperature declines lasted for at least several decades and reenforced the substantial posteruption cooling caused by volcanic aerosols and by a feedback decrease in atmospheric precipitable water. The magnitude and critical location of these temperature declines may have contributed to summer snow survival in the sub-Arctic plateaus and to a consequent triggering of major Pleistocene glaciations.