講演情報
[ACC45-P09]LiDAR surveys for quantifying ice front changes at Taku Glacier, Southeast Alaska
*張 佳晏1,2、杉山 慎2,3、Jason Amundson4、Dougal Hansen5 (1.北海道大学環境科学院、2.北海道大学低温科学研究所、3.北海道大学北極域研究センター、4.南東アラスカ大学、5.セントルイス・ワシントン大学)
キーワード：
氷河、氷河末端変動、ライダー技術、アラスカ
Ice front variations of a glacier can be affected by changes in climatic factors and ice flow. Thus, quantifying these changes give insight into terminus behaviours. By far, previous studies mostly focused on terminus position change in a seasonal- or longer time scale (e.g. Ritchie et al., 2017; Hata et al., 2021; Chang et al., 2024), whilst few highlighted short-term variations. Nowadays, LiDAR (Light Detection and Ranging) technology is implemented in cryosphere research for it allows high resolution measurement of the distance to a target by repeatedly emitting laser light (e.g. Carrivick et al., 2013; Podgórski et al., 2018; Zah et al., 2019). In this study, we quantify the ice front variations of Taku Glacier with a LiDAR sensor during the field campaign in summer, 2025. We discuss possible driving factors by comparing the result with the meteorological data.
Cloud point data were collected on 6/10 (15:36–15:39, UTC−8), 6/13 (09:42–09:45) and 6/16 (08:59–09:02). All data were aligned to the reference cloud (6/10 point cloud) using Iterative Closest Point (ICP) method in CloudCompare (Version 2.13. alpha). The RMSE were 0.49 m (6/13) and 1.63 m (6/16). Stable features, such as sediments and other source of noises, were subsequently excluded. We then calculated the horizontal and vertical displacement in 6/10–6/13 (Period 1) and 6/13–6/16 (Period 2) in MATLAB.
Horizontal displacement (median value) increased by >500% from 0.11 m (standard deviation: 0.40 m) in Period 1 to 0.70 m (std: 1.07 m) in Period 2. Vertical displacement was 0.01 m (std: 0.17 m) in Period 1 and −0.02 m (std: 1.27) in Period 2, suggesting a greater dispersion around the median value in the later period. During the field observation, concentrated rain i.e. cumulative precipitation of 7.5 mm (equivalent to 0.83 mm hr−1) was recorded between 16:36 (6/12) – 01:36 (6/13), whereas little rain was observed in Period 2 (i.e. 0.20 mm). The significant increase in the horizontal displacement in Period 2 was likely linked to the increased ice motion due to substantial precipitation. On the other hand, decrease in vertical displacement can be associated with the enhanced surface melt as a result of warmer temperature in Period 2 (i.e. the average temperature rose by 1.5℃ from 9.5℃ in Period 1 to 11℃ in Period 2). Overall, our finding demonstrates the ability of LiDAR sensor of revealing the short-term ice front changes.
Cloud point data were collected on 6/10 (15:36–15:39, UTC−8), 6/13 (09:42–09:45) and 6/16 (08:59–09:02). All data were aligned to the reference cloud (6/10 point cloud) using Iterative Closest Point (ICP) method in CloudCompare (Version 2.13. alpha). The RMSE were 0.49 m (6/13) and 1.63 m (6/16). Stable features, such as sediments and other source of noises, were subsequently excluded. We then calculated the horizontal and vertical displacement in 6/10–6/13 (Period 1) and 6/13–6/16 (Period 2) in MATLAB.
Horizontal displacement (median value) increased by >500% from 0.11 m (standard deviation: 0.40 m) in Period 1 to 0.70 m (std: 1.07 m) in Period 2. Vertical displacement was 0.01 m (std: 0.17 m) in Period 1 and −0.02 m (std: 1.27) in Period 2, suggesting a greater dispersion around the median value in the later period. During the field observation, concentrated rain i.e. cumulative precipitation of 7.5 mm (equivalent to 0.83 mm hr−1) was recorded between 16:36 (6/12) – 01:36 (6/13), whereas little rain was observed in Period 2 (i.e. 0.20 mm). The significant increase in the horizontal displacement in Period 2 was likely linked to the increased ice motion due to substantial precipitation. On the other hand, decrease in vertical displacement can be associated with the enhanced surface melt as a result of warmer temperature in Period 2 (i.e. the average temperature rose by 1.5℃ from 9.5℃ in Period 1 to 11℃ in Period 2). Overall, our finding demonstrates the ability of LiDAR sensor of revealing the short-term ice front changes.