Combination of geodetic space observations for estimating cryospheric mass changes and their impact on Earth rotation

地球系统中质量的重分布和运动引起地球自转的变化。虽然利用几何空间技术可以高精度地观测到积分激励机制，但从地球子系统中分离出单独的贡献仍然是一个挑战。特别是冰冻圈质量效应的估计，由于没有可靠的冰冻圈地球物理模型和缺乏精确的大地测量观测，存在很大的不确定性。自2002年以来，GRACE卫星任务（重力恢复与气候实验）可以精确地观测到地球重力场的变化。由于地球冰体的空间分布和冰川后陆地的隆升，下伏冰体变化的分离对研究提出了特殊的挑战。自2003年和2010年以来，高度计卫星ICESat（冰、云、陆高程卫星）和CryoSat-2分别可以高精度地观测冰高变化。冰的质量变化需要考虑冰的动力和密度。在这个项目中，首次将几何和重力空间观测结合起来估算冰冻圈质量效应。由于不同大地空间观测的组合，可以补偿单个处理策略的弱点，并可以最优地考虑技术的特定优势。新的改进的发现提供了关于强烈的极地运动是如何受到不断增加的冰融化和相关的海平面上升的影响的信息，以及这种极地运动对地球年平均温度的影响。由于同化了测地估计的角动量，冰冻圈的地球物理模型可以得到改进。

Redistribution and motion of masses in the Earth System cause Earth rotation variations. While the integral excitation mechanism is observed by geometric space techniques with high accuracy, the separation into the individual contributions from the subsystems of the Earth remains a challenge. Especially the estimation of the cryospheric mass effect is afflicted with large uncertainties due to the fact that no reliable geophysical models of the cryosphere exist and due to the lack of precise geodetic observations. Since 2002 gravity field changes of the Earth can be observed precisely by the satellite mission GRACE (Gravity Recovery and Climate Experiment). The separation in particular of the underlying ice mass changes poses a special challenge because of the spatial distribution of the ice masses of the Earth and the postglacial land uplift. Since 2003 and 2010 respectively ice height changes can be observed by the altimeter satellite ICESat (Ice, Cloud, and land Elevaion Satellite) and CryoSat-2 with high accuracy. By the transformation into ice mass changes the ice dynamic and density has to be considered. Within this project for the first time geometric and gravimetric space observations are combined for estimating the cryospheric mass effect. Due to the combination of the different geodetic space observations the weaknesses of the individual processing strategies can be compensated and the technique specific strengths can be optimal accounted. The new improved findings give information about how strong polar motion is influenced by the increasing ice melting and the involved sea level rise and what consequences this polar motion has on the mean annual temperature of the Earth. Due to assimilation of the geodetic estimated angular momenta the geophysical models of the cryosphere could be improved.