Anomalous bottom topography of a small lake in the Larsemann Hills Oasis (East Antarctica)

Abstract

Results of studying the bottom relief of a unique small reservoir (lake) located in the south of the Broknes peninsula, the oasis of the Larsemann Hills (East Antarctica) are presented. The first reliable depth measurements carried out in January 2022 demonstrated that within the shallow basin of the lake (average depth of 1 m or less) there are four narrow depressions (canyons) with a width of 5.5 m or less and a depth reaching 27.7m. Such a character of bottom relief has not been found before in any of the more than 150 known lakes of this oasis. To study this phenomenon, we performed fieldwork including hydrological observations, measurements of water temperature and mineralization at different horizons, high-precision bathymetric survey, and the underwater photography together with geological and geophysical investigations of the lake bank slope. A working hypothesis explaining the origin of such unusual bottom relief suggests a version of frost cracking that propagates along the fracture zone in the bedrock followed by the formation of cryoeluvium and the removal fine-grained particles (suffusion).