3:30 PM - 3:45 PM
[ACC26-06] Terminus dynamics of Taku Glacier, Alaska, during transition from advance to retreat
Keywords:Alaska, glacier, satellite data
Taku Glacier is the largest outlet glacier of the Juneau Icefield, Alaska. This temperate glacier is 55 km long and covers an area of approximately 700 km2. It was the only advancing glacier in the icefield until 2015. However, the glacier’s mass balance has been decreasing since 2013, resulting in a mass loss of 0.8 km3 between 2013 and 2018 (e.g., McNeil et al., 2020). In addition to the mass loss, ~20 m retreat was observed between July 2015 and September 2018, and further retreat is expected in the future (e.g., Zechmann et al., 2020).
To better understand the transition from advance to retreat, we have analysed digital elevation models from ArcticDEM and drone imagery of the glacier terminus region. The ArcticDEM data, which has a 2 m resolution (Porter et al., 2022), spans from 2014 to 2021. The data were downsampled and co-registered by applying the method of Nuth and Kääb (2011). Surface flow velocity of the terminus area was also calculated by applying a feature tracking algorithm (software: OpenPIV) on hillshade images.
The DEMs show a glacier-wide decline in the surface elevation of 2014 to 2021. The change was more pronounced in the near-terminus regions, with a maximum change up to -30 m. Spatial patterns of surface elevation change showed significant year-to-year variations. Further, analysis of near-terminus surface velocities revealed distinct seasonal variations, with acceleration toward the southern margin during summer and lower velocities and motion toward the eastern margin during winter. While velocities in the western area varied from 0.73 m day-1 during summer to 0.28 m day-1 in winter, seasonal variations were less noticeable in the eastern area (between 0.25 m day-1 and 0.39 m day-1).
We have conducted UAV surveys of the glacier terminus since autumn 2021. Images acquired by the UAV were processed to generate high-resolution DEMs and orthorectified mosaic. A comparison of DEMs obtained from UAV surveys in May 2023 and June 2023 indicates a generally decreasing trend in the surface elevation over the area (-1 to -2 m), with the greatest change of -4 m near the southern frontal margin. We also compared the surface elevation change in summers, and similar change patterns appeared for that in 2014 (ArcticDEM data) and 2023 (UAV data). In the presentation, we discuss the detail of the recent glacier change and possible mechanisms driving the elevation and velocity variations.
To better understand the transition from advance to retreat, we have analysed digital elevation models from ArcticDEM and drone imagery of the glacier terminus region. The ArcticDEM data, which has a 2 m resolution (Porter et al., 2022), spans from 2014 to 2021. The data were downsampled and co-registered by applying the method of Nuth and Kääb (2011). Surface flow velocity of the terminus area was also calculated by applying a feature tracking algorithm (software: OpenPIV) on hillshade images.
The DEMs show a glacier-wide decline in the surface elevation of 2014 to 2021. The change was more pronounced in the near-terminus regions, with a maximum change up to -30 m. Spatial patterns of surface elevation change showed significant year-to-year variations. Further, analysis of near-terminus surface velocities revealed distinct seasonal variations, with acceleration toward the southern margin during summer and lower velocities and motion toward the eastern margin during winter. While velocities in the western area varied from 0.73 m day-1 during summer to 0.28 m day-1 in winter, seasonal variations were less noticeable in the eastern area (between 0.25 m day-1 and 0.39 m day-1).
We have conducted UAV surveys of the glacier terminus since autumn 2021. Images acquired by the UAV were processed to generate high-resolution DEMs and orthorectified mosaic. A comparison of DEMs obtained from UAV surveys in May 2023 and June 2023 indicates a generally decreasing trend in the surface elevation over the area (-1 to -2 m), with the greatest change of -4 m near the southern frontal margin. We also compared the surface elevation change in summers, and similar change patterns appeared for that in 2014 (ArcticDEM data) and 2023 (UAV data). In the presentation, we discuss the detail of the recent glacier change and possible mechanisms driving the elevation and velocity variations.