基于Landsat-8影像的北极地区入海冰川流速监测

Landsat-8 OLI因其空间分辨率较高、重复周期适中、高辐射分辨率、高图像获取率（图像质量）的特点，在北极地区大范围冰川流速监测研究中有较大优势。利用2017/2018年格陵兰岛、斯瓦尔巴群岛、北地群岛、法兰士约瑟夫地群岛、德文岛5处北极区域的Landsat-8全色波段数据，采用特征追踪方法提取入海冰川消融期流速。结合MEaSUREs冰川流速数据，分析了198条北极地区入海冰川流速的空间分布特征及其影响因素，同时探究了格陵兰岛Kangerlussuaq冰川流速随时间变化特征。结果表明：与北极其他区域相比，格陵兰岛前缘流速在5~10 m·d^-1及10~20 m·d^-1的入海冰川在数量上最多，最大流速达到了31.62 m·d^-1。而格陵兰岛内部的冰川流速存在差异，北海岸入海冰川平均流速最慢（1.99 m·d^-1），东海岸平均流速（6.13 m·d^-1）大于西海岸（4.14 m·d^-1）。这种流速空间分布差异可能由冰川规模、冰床地势、海流作用、冰盖消融情况等多种因素共同导致。2018年3—10月期间，Kangerlussuaq冰川前缘流速为21.02~22.87 m·d^-1，整体流速为10.02~11.39 m·d^-1。冰川流速在6—7月和9—10月出现峰值，在8—9月出现低谷，主要缘于冰川融水导致的运动加速和冰川物质平衡变化。

Velocity measurement of marine-terminating glaciers in Arctic using Landsat-8 images

Landsat-8 has great advantages in retrieving Arctic glacier surface velocities on a large scale due to its 15 m pixel scale resolution and 12-bit radiometric quantization of OLI band 8， with moderate repetition interval， high image acquisition rate， and high image quality. Based on Landsat-8 panchromatic band images on 2017/2018 of five typical Arctic regions—Greenland， Svalbard， Severnaya Zemlya， Franz Josef Land， and Devon Islands， we have retrieved surface velocities of marine-terminating glaciers during the ablation season using feature tracking method. Combined with MEaSUREs velocity data， we have analyzed the velocity spatial characteristics of total 198 marine-terminating glaciers in Arctic， and reflected the possible forces resulting in the spatial differentiation of velocity distribution. Also， we have analyzed the temporal and spatial velocity characteristics of Kangerlussuaq Glacier on the east coast of Greenland between March and October in 2018. Research shows that Arctic glaciers with front velocities of 5~10 m·d^-1 or 10~20 m·d^-1 mainly lying on the east and west coast of Greenland， and the highest speed reaches 31.79 m·d^-1. Greenland internal velocity diversity is reflected in that average velocity among north coast is the slowest （1.99 m·d^-1）， while east coast （6.18 m·d^-1） is higher than west coast （4.17 m·d^-1）. The spatial differences of glacier velocity may be attributed to glacier scale， bedrock terrain， ice-sea interaction， ice sheet ablation condition or other factors， and the influencing mechanism can be very complicated and intricate. Besides， between April and September in 2018， ice front speed of Kangerlussuaq Glacier is about 21.02~22.87 m·d^-1 and the average glacier center streamline velocity is about 10.02~11.39 m·d^-1. The peak velocity of Kangerlussuaq Glacier appears in June-July and September-October， and the trough appears in August-September， which is mainly due to the glacial meltwater lubrication and glacier mass balance.