Surface Change Monitoring Of Amery Ice Shelf Using Landsat 8 Data Sets

The Antarctic Ice shelves connecting with ice sheet and interacting with the atmospheric and oceans,which is the key to the study of Antarctic Pole.The Lambert Glacier and Amery Ice Shelf system is the largest glacier system in the East Antarctic Ice Sheet.The Amery Ice Shelf,one of the most active areas of the Antarctic,has been a hot spot for research.Ice flow velocity and strain rate are important dynamitic characteristics of the ice shelf,which can be used to analyze the trend of ice shelf changes in time,and contribute to understand and evaluate the glacier-ice shelf system.The ice stream line can reflect the ice flow trajectory of ice shelf.Furthermore,it can be used to analyze the supply source of the ice shelf material.Carrying out ice shelf surface monitoring research is of great significance for predicting the collapse of ice shelves in the future.This paper proposes an ice flow velocity extraction method,which aims to reduce the matching failure caused by the sparse features of the ice shelf,and overcomes the influence of the window size setting on the matching result and the low matching efficiency in the traditional matching method.The ice flow velocity map was used to obtain the vector ice stream line on the surface of the ice shelf,and the strain rate was also calculated.Finally,the ice flow velocity,strain rate and ice stream line were used to analyze the surface change of the Amery ice shelf.Specifically includes the following:(1)In this paper,we develop an improved multi-scale image matching method for producing a complete and accurate Amery ice shelf velocity field from Landsat 8 images.First,we investigate the relationship between the template size and the image entropy and propose an image entropy-based preliminary operation for distinguishing the high-contrast regions from the low-contrast regions prior to iteratively determining the optimum template size.Second,a Gaussian pyramid image-based hierarchical data structure is designed to support a coarse-to-fine image matching strategy.The image entropy-based matching method is applied on the top layer of the image pyramid to guarantee the matching results have optimal completeness and high accuracy.Finally,a postprocess procedure is performed to derive a complete and accurate Amery ice shelf velocity field.(2)The strain rate and the ice stream lines are calculated according to the ice flow velocity.For the extraction of the ice stream lines,the ice velocity data is used.Compared with the slope feature of the DEM or the texture features of the remote sensing image,it will not be influenced by the small change of the slope direction or the lack of texture features,which can derive the complete ice stream lines.Therefore,this paper uses the ice flow velocity to extract the ice stream lines.In this process,it is necessary to follow the three principles of ice stream line extraction: the direction judgment is preferred,the distance between the target pixel and the center pixel is the shortest,and the ice stream lines do not cross each other.For the calculation of strain rate,the ice flow coordinate system is used,and the strain rate distribution of the Amery ice shelf is obtained.(3)The distribution of ice flow velocity and strain rate of the Amery ice shelf was obtained by using the ice flow velocity extraction method and the strain rate calculation method.In addition,this paper focuses on the areas with high velocity or strain rate change,such as the inlet,ice crevasses grounding line area of the Amery ice shelf.It is concluded that the area of the ice shelf with high strain rate and high flow velocity is more likely to have ice crevasses.Then,the flow velocity change and strain rate change of the Amery ice shelf between 2014 and 2018 were obtained to analyze the change trend of the Amery ice shelf in time.It was found that the areas with large changes in strain rate and flow rate were mainly concentrated in the first half of the Amery ice shelf inlet,where also have more ice crevasses.In addition,the 2017-2018 flow velocity data was used to obtain the ice stream lines.These are used analyze the flow trajectory of ice materials and the supply source of it.