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新分布和运动引起地球自转的变化。虽然通过几何空间技术以高精度观察到整体激发机制，但将地球子系统的单独贡献分离仍然是一个挑战。特别是估计的冰冻圈质量效应是深受很大的不确定性，由于事实上，没有可靠的地球物理模型存在的冰冻圈，并由于缺乏精确的大地测量观测。自2002年以来，地球重力场的变化可以通过重力恢复和气候实验（GRACE）使命卫星进行精确观测。由于地球冰块的空间分布和冰后期陆地隆起，特别是底层冰块变化的分离构成了一个特殊的挑战。自2003年和2010年以来，高度计卫星ICESat（冰、云和陆地高程卫星）和CryoSat-2分别可以高精度地观测冰高变化。通过转化为冰质量的变化，必须考虑冰的动力学和密度。在该项目中，首次将空间几何观测和重力观测结合起来，以估计冰冻圈质量效应。由于不同的大地测量空间观测值的组合，可以补偿各个处理策略的弱点，并且可以最佳地考虑技术特定的优势。新的改进发现提供了有关极地运动如何受到冰融化和海平面上升的影响以及这种极地运动对地球年平均温度的影响的信息。由于同化大地测量估计的角动量，可以改进冰冻圈的地球物理模型。

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.