Filling and drainage of a subglacial lake beneath the Flade Isblink ice cap, northeast Greenland

The generation, transport, storage and drainage of meltwater beneath the ice sheet play important roles in the Greenland ice sheet (GrIS) system. Active subglacial lakes, common features in Antarctica, have recently been detected beneath GrIS and may impact ice sheet hydrology. Despite their potential importance, few repeat subglacial lake filling and drainage events have been identified under Greenland Ice Sheet. Here we examine the surface elevation change of a collapse basin at the Flade Isblink ice cap, northeast Greenland, which formed due to sudden subglacial lake drainage in 2011. We estimate the subglacial lake volume evolution using multi-temporal ArcticDEM data and ICESat-2 altimetry data acquired between 2012 and 2021. Our long-term observations show that the subglacial lake was continuously filled by surface meltwater, with basin surface rising by up to 55 m during 2012–2021 and we estimate 138.2 × 106 m3 of meltwater was transported into the subglacial lake between 2012 and 2017. A second rapid drainage event occurred in late August 2019, which induced an abrupt ice dynamic response. Comparison between the two drainage events shows that the 2019 drainage released much less water than the 2011 event. We conclude that multiple factors, e.g., the volume of water stored in the subglacial lake and bedrock relief, regulate the episodic filling and drainage of the lake. By comparing the surface meltwater production and the subglacial lake volume change, we find only ~64 % of the surface meltwater successfully descended to the bed, suggesting potential processes such as meltwater refreezing and firn aquifer storage, need to be further quantified.

Potential technological solution for sampling the bottom sediments of the subglacial lake Vostok: relevance and formulation of investigation goals

The subglacial Lake Vostok in Antarctic is a unique natural phenomenon, its comprehensive study involves sampling of water and bottom surface rocks. For further study of the lake, it is necessary to drill a new access well and develop environmentally safe technologies for its exploration. This article discusses existing and potential technologies for sampling bottom surface rocks of subglacial lakes. All these technologies meet environmental safety requirements and are conducive for sampling. The authors have proposed an alternative technology, using a walking device, which, due to its mobility, enables selective sampling of rocks across a large area from a single access well. The principal issues, related to the implementation of the proposed technology, are investigated within this article. This report is prepared by a team of specialists with many years of experience in drilling at the Vostok Station in Antarctic and in experimental work on the design of equipment and non-standard means of mechanization for complicated mining, geological and climatic conditions.

New large subglacial lake in Princess Elizabeth Land, East Antarctica, detected by airborne geophysical observations

Knowledge of subglacial lakes is important for understanding the stability of the Antarctica Ice Sheet (AIS) and its contribution to the global sea-level change. We designed an intensified airborne campaign to collect geophysical data in Princess Elizabeth Land (PEL), East Antarctica, during the 2015–2019 CHINARE expeditions. We developed an innovative method to build a set of evidence of a newly detected subglacial lake, Lake Zhongshan. Adaptive RES data analysis allowed us to detect the lake surface and extent. We quantified the lake depth and volume via gravity modeling. Another dataset collected at Lake Vostok provided the ground truth. The results revealed that Lake Zhongshan, located at 73°26'53"S, 80°30'39"E and ~3,603 m below surface, has an area of 328 ± 1 km2, making it the only one in PEL and the fifth largest in Antarctica. These findings are important for understanding subglacial hydrodynamics in PEL, as well as the stability of the AIS.

Device for fusion drilling with simultaneous or follow-up reaming of wells in ice

The paper deals with a new opening technology for subglacial reservoirs, which ensures environmentally friendly geological exploration. The technology is based on the results of the first openings of the subglacial Lake Vostok in Antarctica (February 2012 and January 2015). The primary goal of further studies of the subglacial Lake Vostok is to take clean samples of lake water and bottom sediments, which requires direct penetration into the lake. There is a number of conditions to be met in order to conduct further studies of the lake using a clean access well at the Vostok drilling complex. The article summarizes the main results including technological and engineering solutions protected by the patent of the Russian Federation. A detailed consideration is given to a new device for fusion drilling with simultaneous reaming of an ice hole. This device combines two technological processes: drilling due to contact melting, and an increase in the diameter of the well due to the creation of a vortex flow of a continuously heated coolant in the bottomhole zone. The thermal method of ice breaking ensures the ecological cleanliness when opening subglacial reservoirs and is a priority method that favorably differs from the existing ones. The device was named a “thermal drill reamer” (TDR). During the seasonal work of the 64th Russian Antarctic Expedition bench tests of the TDR 132/400 were carried out, the results of which confirmed that the device is capable to ensure 132 mm drilling with simultaneous reaming up to 400 mm.

Multi-omic Characterization of Intraspecies Variation in Laboratory and Natural Environments

Investigation of microbial communities has led to many advances in our understanding of ecosystem function, whether that ecosystem is a subglacial lake or the human gut. Within these communities, much emphasis has been placed on interspecific variation and between-species relationships.

A quantitative method for deriving salinity of subglacial water using ground-based transient electromagnetics

Liquid water can exist at temperatures well below freezing beneath glaciers and ice sheets, where subglacial water systems, fresh and saline, have been shown to host unique microbial ecosystems. Geophysical techniques sensitive to fluid-content contrasts, e.g. electromagnetics, can characterize subglacial water and its salinity. Here, we assess the ground-based transient electromagnetic (TEM) method for deriving the resistivity and salinity of subglacial water. We adapt an existing open-source Bayesian inversion algorithm, which uses independent depth constraints, to output posterior distributions of resistivity and pore fluid salinity with depth. A variety of synthetic models, including a thin (5 m), conductive (0.16 Ωm), hypersaline (147 psu) subglacial lake, are used to evaluate the TEM method for imaging under 800 m-thick ice. The study demonstrates that TEM methods can resolve conductive, saline bodies accurately using external depth constraints, for example, from radar or seismic data. The depth resolution of TEM can be limited beneath deep (>800 m), thick (>50 m) conductive, water bodies and additional constraints from passive electromagnetic (EM) methods could be used to reduce ambiguities in the TEM results. Subsequently, non-invasive active and passive EM methods could provide profound insights into remote aqueous systems under glaciers and ice sheets.

Development of a subglacial lake monitored with radio-echo sounding: case study from the eastern Skaftá cauldron in the Vatnajökull ice cap, Iceland

We present repeated radio-echo sounding (RES, 5 MHz) on a profile grid over the eastern Skaftá cauldron (ESC) in Vatnajökull ice cap, Iceland. The ESC is a ∼ 3 km wide and 50–150 m deep ice cauldron created and maintained by subglacial geothermal activity of ∼ 1 GW. Beneath the cauldron and 200–400 m thick ice, water accumulates in a subglacial lake and is released semi-regularly in jökulhlaups. The RES record consists of annual surveys conducted at the beginning of every summer during the period 2014–2020. Comparison of the RES surveys reveals variable lake area (0.5–4.1 km2) and enables traced reflections from the lake roof to be distinguished from bedrock reflections. This allows construction of a digital elevation model (DEM) of the bedrock in the area, further constrained by two borehole measurements at the cauldron centre. It also allows creation of lake thickness maps and an estimate of lake volume at the time of each survey, which we compare with lowering patterns and released water volumes obtained from pre- and post-jökulhlaup surface DEMs. The estimated lake volume was 250 GL (gigalitres = 106 m3) in June 2015, but 320 ± 20 GL drained from the ESC in October 2015. In June 2018, RES profiles revealed a lake volume of 185 GL, while 220 ± 30 GL were released in a jökulhlaup in August 2018. Considering the water accumulation over the periods between RES surveys and jökulhlaups, this indicates 10 %–20 % uncertainty in the RES-derived volumes at times when significant jökulhlaups may be expected.

Radar sounding survey over Devon Ice Cap indicates the potential for a diverse hypersaline subglacial hydrological environment

Prior geophysical surveys provided evidence for a hypersaline subglacial lake complex beneath the center of Devon Ice Cap, Canadian Arctic; however, the full extent and characteristics of the hydrological system remained unknown due to limited data coverage. Here, we present results from a new, targeted aerogeophysical survey that provides evidence (i) supporting the existence of a subglacial lake complex and (ii) for a network of shallow brine/saturated sediments covering ~170 km2. Newly resolved lake shorelines indicate three closely spaced lakes covering a total area of 24.6 km2. These results indicate the presence of a diverse hypersaline subglacial hydrological environment with the potential to support a range of microbial habitats, provide important constraints for future investigations of this compelling scientific target, and highlight its relevance as a terrestrial analog for aqueous systems on other icy worlds.