Imaging the structures of a subglacial lake D2 in the Antarctic David Glacier catchment from the multi-channel reflection seismic records
Authors: Kang Seung-Goo , Ju Hyeon Tae , Choi Yeonjin , Kwak Hoje , Lee Joohan , Kim Yeadong , Hong Jong Kuk , Lee Jong Ik 
Published: February 2023

&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; David Glacier is a significant East Antarctic outlet glacier through the Transantarctic Mountains and into the western Ross Sea. The six active subglacial lakes (D1~D6) were identified in the David Glacier catchment based on NASA&#8217;s Ice, Cloud, and land Elevation Satellite (ICESat) laser altimeter dataset for 4.5 years (2003-2008). Since 2016, Korea Polar Research Institute (KOPRI) has been preparing the hot-water drilling project in the David Glacier, starting with the geophysical surveys. KOPRI&#8217;s geophysical research team confirmed the change rate of the surface elevation of the David glaciers based on the analysis of the Double-Differential Interferometric synthetic aperture radar (DDinSAR) from satellite (Sentinel-1A) images for July to August 2015 and March 2017, then selected the D2 subglacial lake as the target for the potential hot-water drilling project. KOPRI&#8217;s Antarctic traverse team developed ground routes for logistics from the JBS to the D2 lake site in the 2017-18 season. In the 2018-19 season, a radar survey was conducted on the D2 site, and the lake's global structures and scale were confirmed. Then, in the 2021-2022 season, a multi-channel seismic survey was conducted on the D2 site to image the detailed subglacial structures of the lake. The final goal of this seismic survey is to get information on the optimal site selection for the hot-water-drilling location for subglacial sampling.&#160; The seismic survey was performed for about two months on the ice. Dynamite is used to generating the seismic source; 1.6 kg of dynamites were used per the charging hole. The charging depth is 25 m. 90 m and 180 m shot intervals were used for 8- and 4-fold data acquisition. Four sets of the Geometric Geode and a 96-channel GEOROD system were employed to record the seismic signal from the ice. The group spacing of the receiver (GEOROD) is 15 m. The seismic data were recorded for 4 seconds with two milliseconds sampling rates. The total length of the acquired seismic data is 17.2 km, consisting of 4 survey lines: two south-to-north and two east-to-west lines. The maximum and minimum fold numbers are 8 and 4, respectively. We got high-quality seismic migrated images containing actual structural and geophysical information about the subglacial lake through seismic data processing with advanced denoise and de-ghosting algorithms. We confirmed the thickness of the ice, which can estimate by the depth of the reversed-polarity reflections on the boundaries between the ice and lake water from the migrated seismic sections for each survey line for D2 lake. Also, the 200 m lake water depth, structures, and geophysical characteristics of the subglacial lake were confirmed, and then, we found the optimal hot-water drilling location for the subglacial lake D2 in the David Glacier, Antarctica.