The Stability Of Antarctic Ice Shelves Based On Multisource Data And Numerical Simulation

With climate warming,the Antarctic ice sheet,an important part of the cryosphere,faces with great risks.Subfreezing ice flowing from Antarctica typically forms floating extensions,called ice shelves,before calving icebergs into surrounding seas.As the ice in Antarctic ice sheet is limited by the ice shelves around the ice sheet,the research on the stability of the ice shelves is extremely important.In order to quantitatively analyze the changes of the Antarctic ice shelves under climate change,the research chose the three typical ice shelves in Antarctica to be studied: The Amery Ice Shelf,the Pine Island Glacier Ice Shelf and the Totten Ice Shelf.A model evaluating the stability of ice shelves was built in the research through the numerical simulations of the three ice shelves,which could quantitatively analyse the stability of ice shelves.By collecting and processing Landsat-8 image data,Cryo Sat-2 satellite altimetry data,and the grounding line data,this paper monitored the long-term changes of the three ice shelves.The results showed that under the current climate conditions,the surface mass loss in West Antarctica was obvious,and the thickness of the Pine Island Glacier ice shelf decreased significantly from 2016.With the warming of ocean,the grounding line of the Pine Island Glacier ice shelf retreated significantly;all the three ice shelves calved significantly in recent years,especially the Pine Island Glacier Ice Shelf and the Totten Ice Shelf.The grounding line data and some researches showed that the grounding line of the Pine Island Glacier Ice Shelf retreated significantly,and the bottom of the three ice shelves melted a lot due to the ocean warming.According to the IPCC report,warming of the climate system is unequivocal,and ice temperature would also increase.Elmer/Ice is a finite element simulation software.In this study,steady state simulations of the Amery Ice Shelf,the Pine Island Glacier Ice Shelf and the Totten Ice Shelf were peformed based on the Bed Machine Antarctica v2 data,the ITS＿LIVE data,and the ice temperature data,which included the ice shelves and the glaciers on the up streams of the ice shlves.In the research,an ice shelf and the glacier on the up stream were regarded as an ice shelf system.In the steady state simulations,the ice flow velocities were adjusted to match with the ice flow velocities of the ice shelf main streams.Therefore,the steady state simulations in this study were consifered to fit the natural conditions,which could ensure the results of this research were reliable.In Antarctica,the thickness values of some ice shelves decreased,the grounding lines of some ice shelves retreated,most ice shelved kept calving,and ice temperature would increase with the rising air emperature.Therefore,four kinds of parameters in numerical simulations were setted.In these four kinds of scenarios,the simulations and analysis of the sensitivity of the three ice shelves were performd.we analysed the ice shelf sensitivity through the changes of ice shelf velocities in different scenarios,counted the ice flow velocity response,completed the quantitative analysis of the ice shelf sensitivity,and generated the sensitivity distribution field of the ice shelves to different parameter changes,and found the sensitivity differences in different areas of the ice shelves.The results showed that the increase areas were mainly concentrated in the front of the ice shelves when the ice thickness decreased.The ice flow velocities increased a lot in the areas derived from retreats of grounding lines.The three ice shelves were very sensitive to the retreat of ice shelves.As the warming ice was softened,the ice flow velocities would accelerate.The sensitivity of the ice shelves could also describe the responses of ice flow velocities,which were important parameters to evaluate the stability of an ice shelf.There were two methods to study the stability of an ice shelf.The buttressing theory was a method to analyse the stability of an ice shelf,through which buttressing umber,buttressing force and safety band could be calculated.Changes in the ice flow velocities of the whole ice shelf system could also describe the stability of an ice shelf system.The results showed that the decreasing thickness and the retreats of the ice shelves could extensively reduce the areas that could provide effective buttressing force,and the retreat of ice shelves coud induce the speed-up of ice flow velocities on glaciers.The two parameters in this study were also important to evaluate the stability of an ice shelf.Based on the results of stability and sensitivity analysis,the ice shelf stability evaluation model was established,which included the stability evaluation of the ice shelf and the stability evaluation of the ice shelf system.There were two parts of evaluation systems.The results showed that the ice shelves were relatively stable near the grounding line under the different scenarios.The retreats of the ice shelf would cause the dynamic change of the ice shelf and the speed-up of the ice flow velocities in the whole ice shelf system,thus reducing the stability of the ice shelf and the ice shelf system.The thinning of the ice increased the stress release and thus reduced the effective support area provided by the ice shelf.As ice temperature increased,ice viscosity decreased and ice fluidity increased,thus increasing the ice flow velociteis of ice shelves and ice shelf systems and reducing the stability of ice shelves and ice shelf systems.Combining the two evaluation systems,it can be concluded that the large calving and the retreats of the Antarctica ice shelves would affect the stability of the ice shelves in all aspects and accelerate the mass loss of the Antarctic ice sheet.