Astronomically forced climate changes on Saturn moon Titan

• Applicant: Dr. Tetsuya Tokano
• Subject Area: Astrophysics and Astronomy ; Atmospheric Science
• Term: from 2014 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 262022543

The study shall examine in detail the role of hydrocarbon seas in astronomically forced climate variations on Saturn moon Titan. Seas on Titan are strongly concentrated in the northern polar region, while most basins in the southern polar region are not filled with liquids. This observation led to controversial discussions as to whether the polar seas may represent analogues of ice sheets on Earth, which wax and wane with the Croll-Milankovitch cycle. A regional-scale and global-scale numerical model of methane hydrology will be used to investigate the impact of orbital parameter variations on the global sea distribution and its feedback to the climate. The major working hypothesis of the study is that the mean sea level changes on timescales of the apsidal precession of Saturn due to variable precipitation, evaporation and global transport of methane in the atmosphere. On a regional basis a 3-dimensional ocean circulation model of Titan seas will be applied to investigate how orbital forcing affects circulation and stratification in the seas. These especially include wind-driven circulation and density-driven circulation, which are relevant for variations in the sea surface temperature, sea composition and evaporation. The secular sea level change will be calculated by extrapolating annual sea level changes predicted by a series of simulations run under the orbital parameters of selected epochs in the past. On a global basis a 3-dimensional general circulation model with a built-in atmospheric hydrology scheme and simplified ocean model will be applied to simulate the continuous change in the global sea distribution. The global model particularly addresses the question as to whether polar seas in one hemisphere can expand at the expense of seas in the opposite hemisphere within an orbital cycle or there may be a trend for a preferential accumulation of seas in one of the two hemispheres for geographic or astronomical reasons. Furthermore, the feedback of the variable or invariable sea distribution on the atmospheric part of the climate will be explored by comparing the model predictions with those of a control simulation without seas.

• DFG Programme: Research Grants
• International Connection: USA
• Cooperation Partner: Ralph D. Lorenz, Ph.D.