Astronomically forced climate changes on Saturn moon Titan

这项研究将详细研究碳氢化合物海在土星卫星土卫六上天文强迫气候变化中的作用。泰坦上的海洋强烈集中在北极地区，而南极地区的大多数盆地没有充满液体。这一观察结果引发了关于极地海洋是否可能是地球上冰盖的类似物的争议讨论，冰盖随着克罗尔-米兰科维奇循环而兴衰。将使用区域尺度和全球尺度的甲烷水文数值模式来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。这项研究的主要工作假设是，由于大气中甲烷的不同降水、蒸发和全球运输，平均海平面在土星末端进动的时间尺度上发生变化。在区域基础上，将应用泰坦海的三维海洋环流模式来研究轨道强迫如何影响海洋的环流和层结。这尤其包括风力驱动的环流和密度驱动的环流，它们与海表面温度、海洋成分和蒸发的变化有关。海平面的长期变化将通过外推过去选定时期的轨道参数下运行的一系列模拟所预测的年度海平面变化来计算。在全球范围内，将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。全球模式特别涉及这样一个问题，即在一个轨道周期内，一个半球的极地海洋是否可以以牺牲另一个半球的海洋为代价进行扩张，或者由于地理或天文原因，可能出现在两个半球中的一个半球优先聚集海洋的趋势。此外，通过比较模式预测和无SEA的控制模拟的结果，将探索可变或不变的海洋分布对气候的大气部分的反馈。

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.