[M-IS10] Global climate change driven by the Southern Ocean and the Antarctic Ice Sheet

[MIS10-09] Satellite and field observations on a subglacial lake at Telen Glacier, East Antarctica

*Ken Kondo¹, Masahiro Minowa¹, Shuntaro Hata¹, Satoshi Tanaka², Takeshi Tsuji³, Shin Sugiyama¹ (1.Graduate School of Environmental Science, Hokkaido University, 2.Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3.Department of Systems Innovation, the University of Tokyo)

Keywords:Antarcitica, glacier, ice sheet

Subglacial lakes play an essential role for the dynamics of the Antarctic ice sheet by modulating basal lubrication of the outlet glaciers. For example, subglacial lakes initiate and maintain rapid ice flow of the outlet glaciers (Bell et all., 2007) and their floods cause rapid modification of the subglacial hydrological environment, which results in substantial acceleration of the outlet glaciers (Stearns et al., 2008). Mechanisms of the subglacial lake avtivities and its influences on the ice dynamics are poorly understood because subglacial measurements are difficult. Here, we found a localized decrease of the surface elevation at Telen Glacier, East Antarctica, located at 6 km upstream from its grounding line by satellite data analysis. The surface lowering is similar to the elevation changes seen during the drainage of subglacial lakes (Fricker et al., 2007), suggesting the presence of a subglacial lake at the location. To investigate the detailed activity of the subglacial lake, we conducted satellite observations by measuring glacier surface elevations. Field observations were also conducted as a part of the 65th Japanese Antarctic Research Expedition in January 2024 to survey the subglacial environment.
Telen Glacier is a 3-km wide outlet glacier located 70 km south of the Japanese reasearch base, Syowa Station, East Antarctica. The flow rate is 150 m a⁻¹ at the subglacial lake location which accelerates to 600 m a⁻¹ at the calving front. We found the surface elevation at the subglacial lake location decreased by up to ~6 m during 2015 and 2020. The localized surface lowering was observed over the 7 km² area with a long side of 3.0 km and a short side of 1.5 km. 70 % of the elevation decrease happened from 2015 to 2018, suggesting the subglacial lake drained during the period. The drainage of the subglacial lake suggests the basal hydrological environment is not at a steady state, and active basal water system is presented at the glacier base. During the field observations, 2.4-km long profile was surveyed with active source seismic measurements using reflection method to identify the presence of the subglacial water layer and its thickness. As a result of the seismic survey, strong reflection was found at ~750-m depth, which presumably indicate the reflection from the glacier bed. In the presentation, we introduce the overview of the field campaign and report initial results of the seismic measurements.

Reference:
Bell, R., Studinger, M., Shuman, C. A., Fahnestock, M. A. and Joughin, I. (2007) Large subglacial lakes in East Antarctica at the onset of fast-flowing ice streams, Nature, 445, 904–907.
Fricker, H. A., Scambos, T., Bindschadler, R. and Padman, L. (2007) An Active Subglacial Water System in West Antarctica Mapped from Space, Science, 315(5818), 1544–1548.
Stearns, L. A., Smith, B. E. and Hamilton, G. S. (2008) Increased flow speed on a large East Antarctic outlet glacier caused by subglacial floods. Nature Geosci. 1, 827–831.