Potential significance of land—sea distribution and surface albedo variations as a climatic forcing factor; 180 m.y. to the present

Abstract

The changing distribution and dimensions of continents and the eustatic fluctuations of sea level throughout geologic time have affected the heat balance of the surface of the earth by modifying the surface albedo with respect to the latitudinal imbalance of incoming solar radiation and by modifying the heat transport in the oceans and atmosphere. The results of simple climate models suggest that small variations in the radiation balance result in dramatic climatic changes. An important aspect of the radiation balance is the variation in surface albedo with respect to latitude. We measure the reconstructed land area in 10° latitude belts for the total globe at 20 m.y. intervals, from 180 m.y. to the present, based on plate-tectonic models which include paleogeography. Surface albedo variations are calculated from average land, sea and ice values. These calculations suggest that sea-level fluctuations are potentially the most important factor from the standpoint of the surface energy budget. The area of high-latitude land is less significant. Major changes occur in the relative area of land in desert regions. The high lbedo of these regions suggests that deserts have an important influence on global cooling trends.