Detection Of Antarctic Ice Sheet Mass Change From GRACE Time-variable Gravity Data

The Antarctic ice sheet(AIS)mass balance is closely related to global climate change and sea level change,affected by global warming,the AIS is showing an accelerated melting state,causing the global sea level to continue to rise,seriously affecting the living environment of people in low-altitude areas.Accurate monitoring the mass change of AIS can provide reliable information for understanding and predicting global climate change and sea level change,and provide an important scientific basis for improving human living environment.The successful launch of the GRACE(Gravity Recovery and Climate Experiment)gravity satellite provides an all-weather,high-efficiency,large-scale technology for monitoring the AIS mass change,and has achieved significant results,but the results vary widely.The main reason for the difference is that the uncertainty of the GIA(Glacial Isostatic Adjustment)model and the impact of the leakage error correction method.The accuracy of the GIA model cannot be improved in a short time,so how to effectively correct the Antarctic leakage error will greatly improve the accuracy of the inversion results.Based on the above background,this paper summarizes the sources of leakage-in errors and the corresponding correction methods.Using simulated data to discuss the effectiveness and advantages and disadvantages of the fitting method based on Tikhonov regularization and the global forward modeling method in correcting the Antarctic leakage-out error.The fitting method based on Tikhonov regularization is affected by the boundary expansion and ocean signal within the boundary,the effect of boundary expansion on the correction of the leakage-out error is small;the influence of the ocean signal in the external expansion range is significant,causing the recovery signal distortion in the EAIS.The reason is that the ocean signal is obvious outside the EAIS and is constrained to the adjacent Antarctic land during the fitting recovery process.The global forward modeling recovery method is greatly affected by the leakage of ocean signals around the Antarctic,and the effect is still mainly reflected in the EAIS.This is because the ocean signal outside the EAIS is leaked to the adjacent land area due to the function of truncation and filtering.Causing the initial signal to be inaccurate in the EAIS,and affecting the iterative recovery results.The introduction of the"basin"function to separate the sea and land signals can effectively reduce the impact of the ocean signal on the leakage-out error correction.Using RL05 data provided by CSR,JPL and GFZ to estimate the mass change of the AIS,and analysis the characteristics of mass change from three partitions(WAIS,EAIS and AIS Peninsula)and the 27 drainage systems.The inversion results of the three institutions all indicate that the AIS mass change with a serious regional imbalance.The mass accumulation is mainly concentrated in drainage system 3-9 and 12,the largest accumulation rate is the drainage system 7,and the largest accumulation acceleration is the drainage system 6,which is mainly related to the sudden increase of snowfall.The mass loss is mainly concentrated in drainage system 2,13-15,17 and 20-26,the largest melting rate is the drainage system 21,and the largest melting acceleration is the drainage system 20;the total amount of melting in the drainage system 20,21,22,and 23(Amundsen Sea Embayment)is about-154 Gt/yr,accounting for about 85%of the total melting of the AIS,and the mass reduction in this area is mainly related to glacier flow.Considering the errors in the inversion,the average value of the three institutions is taken as the final result:the melting rate of the AIS is-181.77±41.20 Gt/yr,and the melting acceleration is-6.06±1.27 Gt/yr~2,and a contribution to sea level rise is0.51±0.12 mm/yr,which is in good agreement with the Mascon results.