Investigations of long-term and seasonal scale variations of flow velocity and frontal position of outlet glaciers in Greenland utilizing multi-temporal Landsat imagery

十多年来，冰冻圈及其冰川区域受到了巨大变化的影响。格陵兰冰盖的许多出口冰川目前显示出加速的流速和明显的表面下降，同时保持着实质性的退缩。特别是，终结海洋的冰川表现出一种动力行为，而这种行为没有包括在目前对未来海平面变化的预测中。因此，冰-海边界的入海出海口冰川及其影响因素是本文的主要研究对象。在1972年至2012年期间，格陵兰冰原边缘300多个出口冰川的流速场是可用的。此外，还有100多个冰川的正面位置及其时间变化信息。在项目期内，将利用Landsat7和Landsat8的卫星数据扩展冰川的流速和锋面位置。此外，将纳入预计于2012年开始的哨兵任务的卫星数据。利用这一大型数据档案，将研究流速和冰川前沿位置的长期和季节尺度变化及其相互关系。将特别关注在冰-海边界作用的动态过程。这包括研究前冰期峡湾的冰凌对锋面位置稳定性和流速的影响。为了分析同步冰川变化的区域格局，将结合MODIS数据中海冰形成的年循环和海面温度的信息。在格陵兰北部和东北部地区，将研究40多年来流速的长期演变和终点位置的变化。特别是，将研究观测到的海冰的长期变化和快速成冰对伴有冰架的冰川锋稳定性的影响。利用所有可用的流速场来识别出海口冰川的浪涌事件及其与锋面位置变化和流态时空变异的关系。

For more than a decade, the cryosphere with its glacier regions have been affected by large changes. Many of the outlet glaciers of the Greenland Ice Sheet currently show accelerated flow velocities and a significant surface lowering while sustaining a substantial retreat. In particular, marine-terminating glaciers show a dynamic behavior which is not included in current predictions of the future sea-level change. Thus, the marine-terminating outlet glaciers and their influencing factors at the ice-ocean-boundary are the major research object within the proposal. In the time period between 1972 and 2012 flow velocity fields are available for more than 300 outlet glaciers along the margin of the Greenland Ice Sheet. In addition, information about the frontal position as well as their temporal changes are available for more than 100 glaciers. Within the project term both flow velocity and frontal positions of the glaciers are to be extended using satellite data of Landsat7 and Landsat8. Moreover, satellite data of the Sentinel mission expected to start in 2012 will be incorporated. Long-term and seasonal scale variations of flow velocity and the position of the glacier front as well as their interrelation will be investigated using this large data archive. Special focus will be given on the dynamic processes acting at the ice-ocean boundary. This includes the investigation of the impact of the ice mélange in the proglacial fjord on the stability of the frontal position and on the flow velocity. To analyze regional patterns of synchronous glacier changes information about both the annual cycle of sea-ice formation and sea-surface temperatures derived from MODIS data will be incorporated. In the area of North and Northeast Greenland the long-term evolution of the flow velocity as well as changes of the terminus position for more than four decades will be studied. In particular, the effect of observed long-term changes of the sea ice and fast ice formation on the stability of the glacier front accompanied by an ice shelf will be investigated. All available flow-velocity fields will be used to identify surge events of outlet glaciers and their relation to changes of the frontal position and to changes of the spatial-temporal variability of the flow regime.