Astronomically forced climate changes on Saturn moon Titan

这项研究将详细检查碳氢化合物海洋在土星卫星土卫六上的天文强迫气候变化中的作用。土卫六上的海洋强烈集中在北极地区，而南极地区的大多数盆地都没有充满液体。这一观察结果引发了一场有争议的讨论，即极地海洋是否与地球上的冰盖类似，后者随着克罗尔-米兰科维奇周期的增加和减少而增加。利用区域尺度和全球尺度的甲烷水文数值模型研究轨道参数变化对全球海洋分布的影响及其对气候的反馈。本研究的主要工作假设是，由于降水、蒸发和大气中甲烷的全球运输的变化，土星侧进动的平均海平面在时间尺度上发生了变化。在区域基础上，土卫六海的三维海洋环流模式将用于研究轨道强迫如何影响海洋环流和分层。这些特别包括风驱动环流和密度驱动环流，它们与海面温度、海洋成分和蒸发的变化有关。长期海平面变化将通过外推一系列在过去选定时期的轨道参数下运行的模拟所预测的年海平面变化来计算。在全球范围内，采用内置大气水文方案的三维大气环流模式和简化的海洋模式来模拟全球海洋分布的连续变化。全球模式特别处理的问题是，在一个轨道周期内，一个半球的极地海洋是否会以另一个半球的海洋为代价而扩大，或者由于地理或天文原因，两个半球中的一个可能有优先积累海洋的趋势。此外，通过将模式预测结果与无海的控制模拟结果进行比较，探讨变或不变海分布对气候大气部分的反馈。

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.