A seismic analysis of subglacial lake D2 (Subglacial Lake Cheongsuk) beneath David Glacier, Antarctica

초록

Subglacial lakes beneath Antarctic glaciers are pivotal in advancing our understanding of cryosphere dynamics, basal hydrology, and microbial ecosystems. We investigate the internal structure and physical properties of Subglacial Lake D2 (SLD2), which is located beneath David Glacier in East Antarctica, using seismic data acquired during the 2021/22 austral summer. The dataset underwent a comprehensive processing workflow, including noise attenuation, velocity analysis, and prestack time migration. The migrated seismic sections revealed distinct reverse-polarity reflections at the glacier-lake interface; however, reflections from the lake-bed sediment interface were ambiguous, leading to interpretational uncertainty about the presence of a sediment layer. To resolve this interpretational uncertainty, two alternative structural models were established: Model 1 (no sediment) and Model 2 (with a sediment layer). Synthetic seismograms generated by wave-propagation modeling were compared with field data to validate the subglacial lake structure. The results confirmed the water column thickness to be approximately 82 m (Model 1) or approximately 10 m (Model 2), and possible structural scenarios for the subglacial lake were presented. Additionally, discontinuous reflections detected in seismic sections transverse to the ice flow were interpreted as scour-like feature surfaces formed by ice movement. This study identified the basal structure beneath the subglacial lake, which had been challenging to identify with conventional radar surveys, through seismic surveying. In addition, ambiguous signals in the field seismic data were mitigated via quantitative comparison with synthetic data, thereby facilitating interpretation of the underlying structure. Collectively, these findings enhance our understanding of subglacial lake environments and inform the selection of future drilling sites for in situ sampling.

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