Study On Vertical Deformation Of GNSS Tracking Stations And Mass Change In Arctic

The polar region is the cold source of the global climate,and the changes in the atmosphere and glaciers in the polar region will cause significant changes in the global climate.Therefore,polar research is of great significance for understanding and monitoring changes in global climate and environment.Arctic,has Greenland ice sheet,which is the second largest in the world.Its ice volume accounts for about 10%of the world's total ice.If it is completely melted,global sea level will rise about 6.5 meters.Therefore,study on the geophysical mechanism of the Greenland ice sheet in depth has great practical significance for predicting the mass balance of the Greenland ice sheet and the corresponding sea level changes.GNSS,as an effective technical means,can provide continuous observation data for monitoring mass change in Greenland.It can not only obtain the entire Greenland vertical velocity field including glacial isostatic adjustment,but also contribute to the detection and analysis of sudden changes in Greenland ice mass loss rate.In recent years,with the implementation of the POLENET plan and the expansion of IGS stations,the number and distribution of GNSS stations in Arctic,especially Greenland,have been greatly improved,and have accumulated more than 10 years of data.On the other hand,the GRACE satellite has been providing data for 15 years since its launch in March 2002 for monitoring the mass change of ice and snow.This paper aims to combine GNSS,environmental load displacement and GRACE data to study vertical deformation of the GNSS tracking stations and mass change in Arctic,The main work is as follows:(1)The data of 55 GPS stations in Greenland and surrounding area of the Yellow River Station during 2007-2017 were processed by GAMIT/G10BK10.5 software and the baseline results were combined with the h files of global network(IGS 1?IGS9)provided by SOPAC to obtain coordinate time series of all stations.Outliers were eliminated using Interquartile Range(IQR)rule and the Principal Component Analysis were carried out to weaken the Common Model Error(CME).The vertical velocity of stations were estimated based on Maximum Likelihood Method(MLE)with the white noise and flicker noise and random walk noise considered.(2)The response of GNSS stations to the mass change was calculated using the RL05 version of Monthly Mass Grids-Global mascons data provided by JPL.The elastic load Green function based on the earth's preliminary reference model(PREM)was applied to estimate the displacement response for surface load changes.(3)A noise model suitable for the GNSS coordinate time series in Arctic was established using the observation data of the GNSS tracking stations,and the horizontal and vertical deformation of these stations was analyzed based on this model.The stability of the Yellow River GNSS tracking station was studied thoroughly.The results showed that although the Yellow River GNSS station is built on permafrost,but it has a limited influence on the stability of the station.The horizontal and vertical movement trend of the the Yellow River GPS station is in complete agreement with the NYAL station,only with a difference of 2.15mm/yr in vertical direction.(4)The vertical deformation characteristics of the GNSS tracking station along the coast of Greenland were analyzed by using the vertical displacement rate estimated above.The results showed that all stations of GNET(Greenland Network)showed upward trend and more severe uplifts have been found in the eastern,southeastern and southwestern parts of Greenland.Some stations observed sharp acceleration in the summer of 2010 and 2012,which were mainly related to the increased temperatures,subsurface water temperature,and the increase in black carbon concentrations caused by forest fires.(5)The consistency of GPS time series and the displacements derived from environmental loading was analyzed and the GPS annual changes was corrected by using environmental loading displacements.The correction effect was verified by combining with GRACE data.The results showed that the environmental loading could explain part of the periodic characteristics of GPS time series.Finally,GIA corrections were made to the GPS observed velocities,and relatively high correlations with GRACE were obtained.The impact of current ice and snow mass change on GNET stations was analyzed in sub-regions and found that it is in agreement with the current pattern of glacial mass changes.