Simulation Study for Regional Mass Changes in the Cryosphere Observed by the GRACE Gravity Mission

The GRACE satellite gravity mission provides observations of temporal gravity changes from which the corresponding mass changes on the Earth’s surface can be modeled. The GRACE time series of gravity changes from 2002 until present unveil a lot of information about mass changes in the hydrosphere and in the cryosphere. The official science products of the GRACE mission are monthly global maps of gravity changes, which have been used successfully to study ice mass changes in large-scale areas, such as Antarctica or Greenland. However, regional signals are not necessarily represented in an optimal way since the gravity maps are globally optimized best-fit solutions. With a regional representation, signals can be detected in the time series which have been masked in the global solutions. Regional data analysis approaches have already shown that GRACE measurements can also reveal information about small-scale signals which were not visible in the global solutions. A closed-loop simulation is set up in order to analyze GRACE-type observations regionally. This simulation demonstrates the strengths and shortcomings of the data analysis method as well as the effects of different error sources. In the simulation the focus is on smaller-scale cryospheric signals, such as mass changes of individual ice caps. Consequently, conclusions can be drawn about the observability of different types of glaciological signals, in terms of spatial extend and temporal mass change, by the GRACE gravity mission.