The Role of Mountains, Polar Ice, and Vegetation in Determining the Tropical Climate During the Middle Pennsylvanian: Climate Model Simulations
Bette L. Otto-Bliesner, 2003. "The Role of Mountains, Polar Ice, and Vegetation in Determining the Tropical Climate During the Middle Pennsylvanian: Climate Model Simulations", Climate Controls on Stratigraphy, C. Blaine Cecil, N. Terence Edgar
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During the Middle Pennsylvanian, peat-producing swamps of year-round wetness must have occupied a broad tropical zone based on our knowledge of paleolatitudes of coal deposits formed during this period in North America, Europe, and Ukraine and the absence of growth rings in preserved wood found coexisting in these deposits. Here, we describe a series of global climate model simulations that evaluate the roles of tropical mountains, polar ice, and vegetation in determining the climate over tropical Gondwana. Our results suggest that the tropical mountains played the dominant role in allowing climatic conditions for tropical coal formation. The Central Pangean Mountains acted to impede the July excursion of the Intertropical Convergence Zone (ITCZ) north of the Equator and allowed the tropical everwet band to extend from 10° N to 12° S. The presence of permanent polar ice as a mechanism for increased year-round equatorial rainfall is shown to be less important. Polar ice on the southern supercontinent of Gondwana would have restricted the southward shift of the January tropical precipitation maximum but would have had no effect on the movement back northward in July. Forest vegetation over southern Gondwana would have warmed the southern high latitudes, melting the summer snowcover needed to accumulate into a polar ice sheet. These results define the large-scale boundary conditions necessary for Middle Pennsylva-nian coal formation.