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

Galina Pryakhina,Sergey Popov,Alina Boronina,Ekaterina Ryzhova,Antonina Chetverova,Svetlana Grigoreva

doi:10.1017/jog.2021.58

Abstract

AbstractIn 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 Dålk provoked its overfill and outburst. As a result, a depression of 183 m × 220 m was formed in the place where Lake Dålk 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 Dålk. 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 Dålk. Further research is required to improve our understanding of the lake system responses to changing external factors.

Highlights

The rapid drainage of glacier-impounded lakes is not uncommon for most mountainous and polar regions of the world
We present a phenomenological model of depression formation in the place where Lake Dålk was located
We present the field results obtained in the study of Boulder Lake

Summary

Introduction

The rapid drainage of glacier-impounded lakes is not uncommon for most mountainous and polar regions of the world. Antarctic oases are coastal regions free from ice sheets with areas of several tens to several thousand square kilometres They are typified by distinct microclimates, the existence of seasonal streams, non-freezing lakes, cryogenic soils and biota (Cook, 1900; Kotliakov and Smolyarova, 1990). The expedition staff immediately dug a channel to drainage the water and save the station from flooding (Averyanov, 1965) Another example concerns lakes Razlivnoye and Glubokoe located in the area of the Russian field base Molodezhnaya (Enderby Land, East Antarctica). The depletion of these water bodies is cyclical. Outburst floods occur due to the drainage of lakes in the Bunger Hills, Wohlthat Mountains, Fisher Massif but descriptions are mainly presented in technical reports or Russian scientific journals (Klokov and Verkulich, 1994; Melnik and Laiba, 1994; Dvornikov and Evdokimov, 2017)

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