An Active Subglacial Lake near Vostok Subglacial Lake in East Antarctica Discovered Using ALOS-2 Interferometry

Subglacial lakes, located beneath ice sheets, significantly influence ice dynamics, making the detection of their distribution and the monitoring of their fill and drain activities essential.This study focuses on the high-latitude regions near the Vostok subglacial lake in East Antarctica, an area highly probable for the presence of undiscovered subglacial lakes.We constructed two interferometric pairs of Advanced Land Observing Satellite-2 (ALOS-2) Phased-Array L-band Synthetic Aperture Radar-2 (PALSAR-2) Scanning SAR (ScanSAR) images with a 140-day temporal baseline and applied differential interferometric SAR (DInSAR).A closed circular DInSAR fringe pattern was observed near the Vostok subglacial lake.The DInSAR phase for the region can reflect displacements caused by ice sheet flow and ice surface elevation changes due to changes in the lake' s water level.To reduce the influence of ice flow and estimate the temporal differences in ice sheet elevation changes, we performed a double DInSAR (DDInSAR) technique using the two DInSAR images.The DDInSAR image showed a clearer observation of the closed circular fringe pattern detected in the DInSAR images, and the ice surface elevation observed by the Ice, Cloud and land Elevation Satellite-2 (ICESat-2) within the fringe area showed distinct changes compared to outside the fringe area.This indicates that the circular closed fringe pattern is attributed to changes in the water level of the subglacial lake and the temporal differences in these changes.Although a subglacial lake near the discovered lake has been reported, no surface displacements that could be attributed to changes in the water level of the lake were observed in the ALOS-2 DInSAR and DDInSAR images.Both the discovered subglacial lake and the nearby reported lake exhibited slow rates of water level change.The subglacial water pathways estimated from the hydraulic potential suggest that both lakes are likely to be filled by basal melting of the ice sheet, and the drained water could flow into the Vostok subglacial lake.This study demonstrates the utility of the ALOS-2 ScanSAR interferometry for detecting active subglacial lakes with minimal activity over long periods in the high-latitude inland regions of Antarctica.