The climatic evolution of India and Australia from the Late Permian to Mid-Jurassic; a comparison of climate model results with the geologic record
The climatic evolution of India and Australia from the Late Permian to Mid-Jurassic; a comparison of climate model results with the geologic record (in Pangea; paleoclimate, tectonics, and sedimentation during accretion, zenith and breakup of a supercontinent, George D. Klein (editor))
Special Paper - Geological Society of America (1994) 288: 139-157
The climatic evolution of the Indian and Australian continents from the Late Permian to Jurassic is simulated using a version of the National Center for Atmospheric Research Community Climate Model (CCM). The purpose is to evaluate the effects of changing model boundary conditions on climate for the time of the supercontinent Pangea. The results of four simulations for three time slices (Permian, Triassic, and Jurassic) address the importance of changes in paleogeography (land-sea distribution or topography) and atmospheric CO (sub 2) . The CCM simulations predict significant changes in a number of climatic variables through time. The predominant feature of the Pangean simulations is a pronounced continental seasonality in temperature, especially at mid-latitudes. For India and Australia, the seasonality is most pronounced for the high CO (sub 2) Permian simulation with warm to hot summers and winters well below freezing. As the southern Pangean landmass drifts northward during the Triassic and Jurassic, this seasonality is reduced. In all four simulations, most of the Pangean interior is predicted to be very dry. India and Australia, however, are predicted to be consistently wet, being located on the southern margin of the Tethys Sea. This corresponds well with large coal deposits found on both continents, particularly Australia. A large summer thermal low-pressure cell over the southern hemisphere landmass brings monsoonal rains to the southwestern margin of Tethys (India and East Africa). For the two Permian simulations this monsoonal circulation is sensitive to the presence of seaways and atmospheric CO (sub 2) levels. The simulated summer monsoon is most intense for the Triassic over India, which corresponds well with numerous features in Triassic Indian sediments indicative of a monsoonal climate. The strong winter temperature contrasts between the southern Gondwana landmass and the subtropical Tethys Ocean forces a zone of intense storm activity along the continental margin. This corresponds well with a number of storm deposits found in the geologic record at these locations from the Permian through the Jurassic. The CCM predictions correlate with the paleoclimatic records of India and Australia to a first order over this time interval. The results provide many insights into the sensitivity of climate to boundary conditions typical for the Pangean time period.