喀喇昆仑区域冰川流速变化的时空特征及其对气候和水文变化的响应

Due to its remote location and severe natural environment, the monitoring data of glacier changes in the Karakoram Region are scarce and the observation time is short. Spatial-temporal characteristics of glacier velocity in this region and its response to climate change have not yet been fully understood. Therefore, the glacier velocity is used as a new perspective for the study of "Karakoram anomaly" in this study. The interannual surface velocities of glaciers in the Karakoram over the past 30 years were obtained, and the spatial-temporal characteristics of glacier velocity were analyzed and its response to climate change and glacial lake change. The main research contents of this study are summarized as follows. (1) The active and passive remote sensing images were used to derive the interannual glacier velocity in the Karakoram over the period 1990-2020. The surface velocities that obtained from different data were compared and validated with each other. Moreover, the terminus of glaciers and the glacial lakes of the typical glaciers in this region were extracted from the remote sensing images. (2) The changes in glacier velocity of nonsurge-type glacier in the Karakoram based on the interannual glacier velocity in the past 30 years were analyzed. Combining with climate factors such as temperature and precipitation, the influence of temperature and precipitation on the velocity was analyzed. Furthermore, the relationships between the changes of glacier velocity and the changes of glacial lakes of the typical glaciers in this region were investigated. (3) Based on the interannual glacier velocity and the changes of glacier terminus, the surge-type glaciers in the region are identified, and the surge cycle of the glaciers was inferred according to the repeated surge events. Research results of this project should be of the great significance to understanding the "Karakoram anomaly" and early warning the disasters of the surge-type glaciers.

喀喇昆仑区域地处偏远、自然环境险恶，冰川变化监测资料稀少且观测时间较短，迄今为止，该区域长时间序列冰川流速时空变化特征及其对气候的响应关系知之甚少。本课题以冰川流速作为“喀喇昆仑异常”研究的新视角，获取该区域近30年的年际冰川流速，分析冰川流速时空变化特征及其对气候变化和冰面湖变化的响应。主要研究内容为：（1）基于主被动遥感影像提取1990年以来喀喇昆仑区域稳健年际冰川流速，对不同数据获取的冰川流速进行对比验证，并根据遥感影像提取冰川末端边界及典型冰川冰面湖信息。（2）分析该区域非跃动冰川流速随时间变化特征，结合气温和降水等气候因子，分析气温和降水对该区域非跃动冰川流速的影响，并分析典型冰川流速变化与冰面湖变化之间的关系。（3）结合年际冰川流速和冰川末端边界变化，识别区域内的跃动冰川，根据重复跃动推测跃动冰川的跃动周期。研究成果对于认识“喀喇昆仑异常”和跃动冰川灾害预警具有重要的科学意义。

喀喇昆仑区域冰川物质平衡的研究发现，近年来喀喇昆仑区域冰川物质增加或处于平衡状态，但受实地观测和遥感监测技术限制，该区域的物质平衡结果一般为十年际或者更长时间，难以准确捕捉该地区冰川变化异常信号。冰川运动速度是研究冰川动力学、物质平衡和气候变化的重要参数，并对冰川灾害研究亦具有重要意义，本课题以冰川流速变化作为“喀喇昆仑异常”研究的新视角，基于多源遥感数据，获取了喀喇昆仑区域冰川长时间序列的年际表面流速，分析了喀喇昆仑区域冰川流速变化的时空特征及其对气候变化的响应，主要研究成果概述如下：（1）发展和优化了冰川流速提取方法，利用一年内多期数据提取冰川流速，并将多期流速结果融合生成年平均流速，提高了流速结果的稳健性，基于此获得了1990-2020年喀喇昆仑区域年际冰川表面流速；（2）将Landsat ETM+ SLC-OFF数据获取的流速结果与同期的ASAR数据和Landsat TM数据获取的结果进行对比，验证了SLC-OFF数据提取喀喇昆仑区域冰川流速的可靠性；（3）分析喀喇昆仑区域非跃动冰川流速时间变化特征，发现非跃动冰川流速在1990-2000年期间呈减小趋势，在2000-2020年则是增加趋势，与该区域物质平衡研究结果一致，结合气温和降水数据发现，该区域非跃动冰川流速变化可能受夏季温度和年降水变化的影响；（4）通过长时间序列流速变化发现该区域多数跃动冰川存在明显的跃动期和平静期，分析Kyagar冰川和音苏盖提冰川的多次跃动事件，发现跃动周期约为20年。研究成果对于认识“喀喇昆仑异常”以及预测未来该区域的跃动事件和冰川灾害预警方面具有重要的意义。