Formation of a large ice depression on Dalk Glacier (Larsemann Hills, East Antarctica) caused by the rapid drainage of an englacial cavity

In the afternoon of 30 January 2017, a catastrophic outburst flood occurred in the Larsemann Hills (Princess Elizabeth Land, East Antarctica). The rapid drainage of both a thin supraglacial layer of water (near Boulder Lake) and Lake Ledyanoe into the englacial Lake Dalk provoked its overfill and outburst. As a result, a depression of 183 m x 220 m was formed in the place where Lake Dalk was located. This study summarises and clarifies the current state of knowledge on the flood that occurred in 2017. We present a phenomenological model of depression formation. We specify the reasons for the outburst of the system of lakes Boulder, Ledyanoe and Dalk. In addition, we carry out mathematical modelling of the outburst of each of the three lakes and estimate the flood severity. Outburst hydrographs, channel diameters, volume and duration of floods were calculated. Particular simulation results were validated with field data. In conclusion, we give an overview of the new outburst cycle of the lake system, which began in 2020 with the drainage of the lakes Boulder and Ledyanoe, and the new formation of Lake Dalk. Further research is required to improve our understanding of the lake system responses to changing external factors.

Automated summary

In 2017, a catastrophic outburst flood occurred in the Larsemann Hills in East Antarctica, resulting in a large depression forming where Lake Dalk was located. A phenomenological model of depression formation was proposed, and reasons for the outburst of the lake system were specified. Mathematical modeling and field data validation were used to estimate flood severity.