Change trend of debris-free glaciers in the Pamir based on Google Earth Engine from 1990 to 2020
The Pamir Plateau is the largest center of glaciation in the high mountain regions of Asia. Glacial melt water plays a key role in regional water resources and water cycle. However,in recent years,there are still controversies about the understanding of glacier changes in the Pamir Mountains. On the one hand,it is believed that there is an abnormal progression of glaciers in the Karakoram Pamir Mountains Plateau. On the other hand,it is believed that the glaciers in the Pamir Plateau are accelerating their retreat. The reasons for this are twofold:firstly,there is a mismatch in the spatiotemporal scope of the study,and secondly,there are differences in the definition of glaciers in the study. Based on this,in order to understand the trend and magnitude of glacier changes in the Pamir Mountains,this study,based on multi-source remote sensing images and the Google Earth Engine (GEE) platform,constructed a glacier discrimination method combining the multi temporal minimum NDSI and the classification algorithm of glacial surface moraine area,automatically extracted the area change se-quence of debris-free glaciers in the Pamir Mountains from 1990 to 2020 without surface moraine coverage,and analyzed the spatio-temporal change characteristics and trends of debris-free glaciers in the region,And clarify whether there is a phenomenon of "Pamir Karakoram Glacier Anomaly". This study provides a profound expla-nation of the current changes in glaciers in the Pamir region,which can effectively support regional water re-sources and ecological environment protection. In order to clarify the spatiotemporal changes of debris-free gla-ciers in the Pamir Mountains in the past three decades,this study,based on the GEE platform,combined image cloud cover,seasonal snow cover,moraine cover at the end of the glacier and other factors,obtained the spatio-temporal changes of high-resolution debris-free glaciers in the Pamir Mountains in the past 30 years. The results indicate that the combination of GEE cloud computing platform and glacier classification algorithm is effective and feasible for quickly extracting glaciers,improving the efficiency of long-term glacier change research. Dur-ing 1990—2020,the area of debris-free glaciers on the Pamir Mountains showed a general shrinking trend. In the past 30 years,the area of debris-free glaciers has shrunk from (12108.98±250.38) km2 to (8616.44±7.22) km2,with an average reduction rate of 116.42 km2·a-1. The area of naked glaciers in the west of Pamir Moun-tains Plateau generally shows a shrinking trend,while the area of debris-free glaciers in the east of Pamirs is rela-tively stable,the shrinking rate is relatively small,and some regions show an increasing trend during 2000—2010. There is an abnormal phenomenon of Pamirs glaciers. Since 2010,the area of glaciers began to decrease,and the abnormal phenomenon of Pamirs glaciers no longer exists. Based on the analysis of DEM data in Pamir Mountains,it is found that the distribution of debris-free glacier area in Pamir Mountains is normal with altitude,and the largest debris-free glacier area occurs at 4900～5200 m altitude. Since 1990,the reduction in debris-free glacier area has mainly occurred in mid altitude areas of 4600～5500 m,and has decreased towards high and low altitude sides. Based on the analysis of climate and glacier elevation changes,it is concluded that the glacier anomaly on the Pamir Mountains from 1990 to 2010 is caused by the thinning of the glacier thickness and the gla-cier jumping at the end of the glacier. This article explores the combination and application of high-performance algorithms and large-scale remote sensing data resources from cloud computing platforms with traditional band combination algorithms,enabling GEE to play a more important role in large-scale research such as the entire high Asia region to global glacier changes,and providing new ideas for large-scale spatial scale research and effi-cient data processing.
Google Earth EnginePamirdebris-free glacierglacier anomaly
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