Chinese Journal of Polar Research ›› 2020, Vol. 32 ›› Issue (2): 164-176.DOI: 10.13679/j.jdyj.20190029

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Extraction of seasonal surface ablation zones in the Dalk Glacier (Antarctica) based on Landsat-8 images

Qu Yutong1,2, Cheng Xiao1,2,3,4, Liu Yan1,2,4   

  1. 1.State Key Laboratory of Remote Sensing Science, College of Global Change and Earth System Science(GCESS), Beijing Normal University, Beijing 100875, China;
    2.University Corporation for Polar Research (UCPR), Beijing 100875, China;
    3.School of Geomatics Science and Technology, Sun Yat-sen University, Zhuhai 519082, China;
    4.Southern Marine Science and Engineering Guangdong Laboratory, Zhuhai 519082, China
  • Received:2019-06-03 Revised:2019-09-22 Online:2020-06-30 Published:2020-06-30

Abstract:

Ice sheet surface ablation is a sensitive indicator of climate change and global warming. The melting of ice and snow will reduce the surface albedo and affect the global energy balance. Surface melt water will increase the propagation of cracks, reduce the stability of the ice shelf and affect the material balance of the ice sheet. At present, the lack of high-temporal resolution data on the distribution of ablation zones limits the in-depth exploration of the mechanism and spatial-temporal characteristics of Antarctic ice sheet ablation. Focusing on the research of the extraction of the large-scale ablation zone(blue ice, wet snow and melt water) of the Antarctic ice sheet, an automatic ablation zone extraction method based on the MNDWIice (Modified Normalized Difference Water Index Adapted for Ice,) is proposed. Using Landsat-8 data with a resolution of 30 m at 18 scenes from September 2016 to April 2017, the MNDWIice threshold automatically extracted from the ablation zone was obtained, and the seasonal ablation information extraction and analysis with high spatial resolution were realized by taking the Dalk Glacier in the east Antarctic as an example. The results show that: Under the condition of less cloud and terrain shadow interference, the MNDWIice calculated based on the Landsat-8 reflectance data uses a single threshold (0.136) to extract the ablation zone with an accuracy of 67.7% —94.2%, and the average accuracy is 81.5 %; The ablation area of Dalk Glacier and the mean value of MNDWIice in the ablation zone show obvious seasonal spatiotemporal changes; Ablation occurred no later than the earlier time of Landsat-8 data observation (September 7); Ablation first appeared and mainly occurred at the eastern ground line where the terrain dropped sharply.

Key words: Antarctica, Dalk Glacier, ablation, MNDWIice