Spatio-temporal analysis of the ice mass changes over Greenland from GRACE and GRACE-FO.

Prediction of the trends of ice mass loss in Greenland can help for understanding what occurred during the last 20 years and in the future. The Level-2 GRACE and GRACE-FO solutions provided by the official computing centres CSR and ITSG as well as the combined products of the COST-G project give access to the spatio-temporal variations of the ice mass balance of Greenland from 2002 to present. We first reduce the GRACE data from post-glacial rebound. We propose to analyse these solutions by applying Singular Value Decomposition (SVD) and Empirical Mode Decomposition (EMD) to extract the trend. This trend is then removed from the timeseries for the Fast Fourier Transform (FFT) and 1-D Continuous Wavelet Transform (CWT) analysis. CWT and FFT analysis enable to unravel the long-term trend of the ice loss ranging from 6-9 years, as well as the annual and semi-annual part. The period of 6 to 9 years shows some correlation with meteorological and climate indexes such as North Atlantic Oscillation (NAO). The spatial component of the first SVD mode indicates that the ice melting is the most important along the west and southeast coast at the rate of -30 to -40 Gt/yr. Globally, the trend is not linear, it consist of different phases of acceleration and deceleration with rates between -60 and -340 Gt/yr.