Permian Megamonsoon Sensitivity to Paleo-Tethys Warm Pool: Model Simulations using CCSM3

Abstract. Simulations of the late Permian (251Ma) are analyzed with respect to the northern hemispheric Pangean megamonsoon. We find that the presence and spatial distribution of the warm pool, and not land-sea temperature differences, are the primary forcing agents for the megamonsoon. The land-sea temperature gradient, as a monsoonal mechanism, is tested by eliminating the Cathyasian peninsula and is found to have little impact on the spatial character of the monsoon. Furthermore, the response of the monsoon to the warm pool was tested by removing all Paleo-Tethys equatorial islands, which allows the warm pool to expand and migrate westward thus shifting the pattern of monsoonal precipitation. Additionally, different CO₂ regimes are presented, in which a 10-fold change in forcing produces diverging climates and therefore different warm pool and monsoon locales. Atmospheric mass flux for the monsoonal regime is characterized and shown to change with warm pool movement. Tropical and equatorial ocean currents impact the seasonal progression and location of the warm pool. Experiments were conducted using the low-resolution version of Community Climate System Model, Version 3 (CCSM3) in both coupled and fixed sea surface temperature (SST) context. For validation purposes, a modern control is briefly presented with observations and is shown to represent both the spatial and seasonal progression of the Indian monsoon.