Abstract
Satellite gravimetry data acquired by the Gravity Recovery and Climate Experiment (GRACE) allows to derive the temporal evolution in ice mass for both the Antarctic Ice Sheet (AIS) and the Greenland Ice Sheet (GIS). Various algorithms have been used in a wide range of studies to generate Gravimetric Mass Balance (GMB) products. Results from different studies may be affected by substantial differences in the processing, including the applied algorithm, the utilised background models and the time period under consideration. This study gives a detailed description of an assessment of the performance of GMB algorithms using actual GRACE monthly solutions for a prescribed period as well as synthetic data sets. The inter-comparison exercise was conducted in the scope of the European Space Agency’s Climate Change Initiative (CCI) project for the AIS and GIS, and was, for the first time, open to everyone. GMB products generated by different groups could be evaluated and directly compared against each other. For the period from 2003-02 to 2013-12, estimated linear trends in ice mass vary between −99 Gt/yr and −108 Gt/yr for the AIS and between −252 Gt/yr and −274 Gt/yr for the GIS, respectively. The spread between the solutions is larger if smaller drainage basins or gridded GMB products are considered. Finally, findings from the exercise formed the basis to select the algorithms used for the GMB product generation within the AIS and GIS CCI project.
Highlights
The Climate Change Initiative (CCI) programme, set up by the European Space Agency (ESA), aims at the provision of reliable, long-term, satellite-based data products to investigate and manage climate change [1]
The present study demonstrates the need for a comprehensive exercise, i.e., the incorporation of an extended set of synthetic data and the analyses of both basin and gridded Gravimetric Mass Balance (GMB) products, for a rigorous assessment of the differences between the results derived by various algorithms
Three different methods were applied in different variants, namely, regional integration approaches (RI), a forward modelling technique (FM) and different mass concentration methods (MC)
Summary
The Climate Change Initiative (CCI) programme, set up by the European Space Agency (ESA), aims at the provision of reliable, long-term, satellite-based data products to investigate and manage climate change [1]. Two different types of Gravimetric Mass Balance (GMB) products are provided by the CCI ice sheets projects: (1) time series of monthly mass changes for the entire ice sheets and individual drainage basins, describing the evolution in ice mass (GMB basin product), and (2) time series of monthly mass change grids covering the entire ice sheet (GMB gridded product), both relative to an arbitrary reference value. Both GMB products are described in detail in the corresponding product user guide [4,5]
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