Analysis Of Mass Change In Greenland And Its Subregions Based On GRACE Data

Glaciers are closely related to climate.Greenland,as the second largest continental glacier in the world after Antarctica,is melting rapidly,resulting in the continuous rise of sea level.The study on the mass change of Greenland ice sheet provides an important basis for the study of climate change and sea level change.The launch of GRACE(gravity recovery and Climate Experiment)gravity satellite provides all-weather,stable and long-time scale observation information for the study of polar glacier mass,and has produced many meaningful studies.This thesis summarizes the common filtering methods of grace time-varying gravity field spherical harmonic coefficient data,as well as the sources and correction methods of leakage error.In order to study the applicability of different methods in Greenland,a simulation experiment is designed based on mascon(mass concentration)and noise data to explore the recovery effect of leaked signal from different scales.At the overall scale of Greenland,both the forward modeling and the scale factor can significantly recover the leakage error in the time series,improve the amplitude and trend term of the signal and approach the simulation value.However,in terms of spatial distribution,the scale factor cannot reflect the spatial characteristics of fast ablation rate in the southwest region of the original signal and partial mass accumulation in the inland region,because the actual signal does not meet the assumption of uniform change of regional mass in the scale factor.At Greenland subwatershed scale,the scale factor has poor correction effect on mutual leakage between watersheds because it does not estimate and deduct the internal leakage.The effect of forward modeling and data-driven method is better,among which the data-driven method has better correction effect on the phase of inter watershed leakage and time series.Based on the conclusion of simulation experiment,GRACE RL06 time-varying gravity field model solved by CSR(space research,University of Texas at Austin),GFZ(German Research Centre for Geoscience)and JPL(Jet Propulsion Laboratory)is selected to settle the mass change of Greenland.The inversion results of the three institutions are relatively close,indicating that the ice sheet in Greenland is melting rapidly and the speed is accelerating,The average mass change rate of the three mechanisms is about-232.81 Gt/a.The mass change shows strong regional characteristics.The coastal area with most high-speed flowing glaciers has the fastest mass loss.The average equivalent water height change in the West and South can reach-20 cm/a.the glacier ice cover in the north is relatively small,extensive and slow,such as Nioghalvfjerdsfjorden,Zachariae Isstr(?)m and Storstr(?)mmen.The mass change rate in the inland area is much lower than that in the coastal area,And the mass of some areas is increasing cumulatively.The ice mass change in the area within 110 km of Greenland boundary is about-160 Gt/a.It can be seen that 70% of the mass loss occurs in the coastal area,and the signal leakage of the whole island mainly occurs in this area.The comparison between GRACE and GPS stations shows that the two results are consistent in the general long-term trend,and the ice sheets near the four stations are losing rapidly.