| The cryosphere is one of the five major circles affecting the climate system and also the most severely affected by climate warming,and the ice sheet is the largest component of the cryosphere.The ice sheet is mainly composed of two major ice sheets,the Antarctic ice sheet and the Greenland ice sheet,with the Antarctic ice sheet accounting for about90%of the total.The study of the cryosphere can provide a basis for human climate risk assessment,adaptation and decision making,and help translate information on natural changes in climate（heat,cold,rain,drought,snow,wind,coastal flooding,etc.）in order to make them meaningful to society and ecosystems.The Antarctic ice sheet is an important indicator of climate change.It stores about27 million cubic kilometers of ice,which accounts for about 90%of the total global ice volume and 70%of the freshwater reserves,and if all of it melts enough to raise sea level by 58 m.Just a slight change in the Antarctic ice sheet will have a profound impact on the global environment.The total mass of the Antarctic Peninsula and West Antarctic ice sheets is lost cumulatively,the loss is accelerating from 2006 to 2020,and is particularly severe in the West Antarctic ice sheet,contributing 63%of the Antarctic ice sheet loss,dominated by accelerated glacier flow,while accelerated flow across the West Antarctic in Amundsen Gulf,the Gates Ice Shelf,and the West Antarctic Peninsula at the Margaret Bay touchdown line accounts for 88%of this increase.Numerical simulations have become an important tool for understanding the evolution of the Antarctic ice sheet.Numerical ice sheet simulations can reveal the physical processes of the ice sheet and have become an important way to understand the past evolution of the ice sheet,to explain the causes of the present ice sheet formation and to predict the future evolution of the ice sheet.Marie Byrd Land,located in West Antarctica,is the largest uninhabited area on Earth,and there is a lack of research on glaciers in this area due to the abnormally harsh climatic conditions.Numerical simulations of Marie Byrd Land can deepen the understanding of this region,and at the same time help to understand the causes of the accelerated loss of the West Antarctic ice sheet and summarize its change pattern,which is of far-reaching significance to the study of Antarctica.In this paper,based on the bottom elevation and surface elevation data of the Antarctic ice sheet in the 2021 update of Bed Machine V2,we add the boundary conditions of surface temperature,surface mass balance and geothermal flux,and use the Full-Stokes three-dimensional model Elmer/Ice to conduct steady simulations of the West Antarctic Marie Byrd Land（76.8°S～77.3°S,138°W～142°W）region.The parameters of the basal friction coefficient and Glenn enhancement factor in Elmer/Ice were constrained by the remotely sensed surface ice flow data（MEa SUREs In-SAR-Based Antarctica Ice Velocity Map）from the MEa SUREs project updated in 2020 by the National Snow and Ice Data Center.The constraint uses the root mean square error（RMSE）between the simulated and remotely sensed surface ice flow velocities as an evaluation index to obtain the best parameters suitable for regional simulations.The minimum RMSE(RMSE=4.1408 m·a-1)is obtained when the basal friction coefficient is 0.1 and the Glenn enhancement factor is 0.26,and the experimental results of velocity,temperature and stress fields of the ice cover are obtained by simulating with these parameters.Finally,the results of diagnostic simulation experiments are used as input parameters for prognostic simulations to observe the future changes of the ice sheet.The main research contents of this paper are as follows:1.Conducting numerical simulations of synthetic glacier using Elmer/Ice.By adding different boundary conditions and solvers,changing the values of input parameters,studying the effect of different boundary conditions and parameters on the numerical simulation.2.The parameters of the ice sheet in Elmer/Ice are constrained by remotely sensed ice sheet surface velocity data from the MEa SUREs project,to inverse the Glen enhancement factor and basal slip coefficient needed for the prognostic simulation.The diagnostic simulation of the Marie Byrd Land is carried out to expore the dynamic and thermodynamic characteristics of the ice sheet,to research the sensitivity of geothermal flux uncertainty to the dynamics and thermodynamics of Marie Byrd Land ice sheet.3.The parameters and results obtained from the diagnostic simulation are used as the initial conditions to do the prognostic simulation,observe the future change trend of the ice sheet,and evaluate its impact on the accelerated change of the West Antarctic Ice Sheet and its impact on sea level rise. |
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