09:15 〜 09:30
[ACC25-02] Drone survey for precise DEM construction and supraglacial stream mapping on Qaanaaq Glacier, northwestern Greenland
Greenland is currently affected by rapidly warming climate in the Arctic, which causes melt increase and retreat of glaciers situated along the coast. To better understand the processes driving the glacier change, we have been studying Qaanaaq Ice Cap in northwestern Greenland since 2012. As a part of the field campaign in the summer of 2022, we conducted drone observations over Qaanaaq Glacier, an outlet glacier of the ice cap.
We focused on the process of supraglacial stream development, which plays a significant role in the glacier runoff processes. These streams are also important for energy exchange on the glacier surface because water flowing through channels loses energy by viscous dissipation and provides heat for melting of ice. Field observation to acquire high-resolution images is important to study the processes because satellite imagery does not provide sufficient resolution to observe supraglacial stream changes.
The survey took place for seven days between July 14 and August 11. A drone (DJI phantom4pro V2.0) was operated at 120 m above the glacier to take images with a resolution of 33 mm per pixel. Six painted wooden plates were distributed on and around the glacier, which were surveyed with kinematic GNSS positioning to improve the accuracy of the drone survey. Repeated surveys were carried out at an elevation of 720 m a.s.l. over an area of 9.14´105 m2 to monitor changing glacier surface features. 677 images were acquired during each of six surveys. The images clearly indicate the evolution of supraglacial streams, which are considered to be important for ice melt as well as glacier hydrology. The images were processed with software (Agisoft Metashape) to generate an orthorectified mosaic image and construct a DEM. seven DEMs and orthorectified mosaic image were created for each observation day.
By comparing these DEMs, we calculated the surface elevation change of the glacier. The mean surface elevation change of the glacier from July 26 to August 10 was 0.68 m. The loss in elevation was particularly significant along a supraglacial stream and glacier margins, with a maximum change of 1.8 m. The DEMs were compared with surface elevation data obtained by kinematic GNSS survey. The validation against the GNSS data showed that the mean error of the DEM on July 26 and August 10 were 0.07 m (standard deviation 0.27 m) and 0.11 m (standard deviation 0.35 m). More detailed analysis on the DEMs is under progress. In the presentation, the mechanism of the elevation change and the evolution of supraglacial streams will be reported.
We focused on the process of supraglacial stream development, which plays a significant role in the glacier runoff processes. These streams are also important for energy exchange on the glacier surface because water flowing through channels loses energy by viscous dissipation and provides heat for melting of ice. Field observation to acquire high-resolution images is important to study the processes because satellite imagery does not provide sufficient resolution to observe supraglacial stream changes.
The survey took place for seven days between July 14 and August 11. A drone (DJI phantom4pro V2.0) was operated at 120 m above the glacier to take images with a resolution of 33 mm per pixel. Six painted wooden plates were distributed on and around the glacier, which were surveyed with kinematic GNSS positioning to improve the accuracy of the drone survey. Repeated surveys were carried out at an elevation of 720 m a.s.l. over an area of 9.14´105 m2 to monitor changing glacier surface features. 677 images were acquired during each of six surveys. The images clearly indicate the evolution of supraglacial streams, which are considered to be important for ice melt as well as glacier hydrology. The images were processed with software (Agisoft Metashape) to generate an orthorectified mosaic image and construct a DEM. seven DEMs and orthorectified mosaic image were created for each observation day.
By comparing these DEMs, we calculated the surface elevation change of the glacier. The mean surface elevation change of the glacier from July 26 to August 10 was 0.68 m. The loss in elevation was particularly significant along a supraglacial stream and glacier margins, with a maximum change of 1.8 m. The DEMs were compared with surface elevation data obtained by kinematic GNSS survey. The validation against the GNSS data showed that the mean error of the DEM on July 26 and August 10 were 0.07 m (standard deviation 0.27 m) and 0.11 m (standard deviation 0.35 m). More detailed analysis on the DEMs is under progress. In the presentation, the mechanism of the elevation change and the evolution of supraglacial streams will be reported.