SURFACE ALBEDO INCREASE FOLLOWING MASSIVE PLEISTOCENE EXPLOSIVE ERUPTIONS IN WESTERN NORTH-AMERICA

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. © 1979.