Environmentally clean access to Antarctic subglacial aquatic environments

AbstractSubglacial Antarctic aquatic environments are important targets for scientific exploration due to the unique ecosystems they support and their sediments containing palaeoenvironmental records. Directly accessing these environments while preventing forward contamination and demonstrating that it has not been introduced is logistically challenging. The Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project designed, tested and implemented a microbiologically and chemically clean method of hot-water drilling that was subsequently used to access subglacial aquatic environments. We report microbiological and biogeochemical data collected from the drilling system and underlying water columns during sub-ice explorations beneath the McMurdo and Ross ice shelves and Whillans Ice Stream. Our method reduced microbial concentrations in the drill water to values three orders of magnitude lower than those observed in Whillans Subglacial Lake. Furthermore, the water chemistry and composition of microorganisms in the drill water were distinct from those in the subglacial water cavities. The submicron filtration and ultraviolet irradiation of the water provided drilling conditions that satisfied environmental recommendations made for such activities by national and international committees. Our approach to minimizing forward chemical and microbiological contamination serves as a prototype for future efforts to access subglacial aquatic environments beneath glaciers and ice sheets.

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Hot-Water Drilling in the Antarctic Peninsula (Abstract)

Annals of Glaciology ◽

10.1017/s0260305500006777 ◽

1988 ◽

Vol 11 ◽

pp. 215

Author(s):

S. Cooper

Keyword(s):

Antarctic Peninsula ◽

Temperature Sensors ◽

Back Pressure ◽

Hot Water ◽

Ice Shelves ◽

Pilot Hole ◽

Fast Ice ◽

Drilling System ◽

The Antarctic ◽

Practical Field

The British Antarctic Survey has developed a hot-water drilling system used chiefly for installing temperature sensors through ice shelves and for retrieving oceanographic equipment tethered through thick fast ice. The specification, design and operation of the drill for these two activities will be discussed and practical field problems will be highlighted. A novel aspect of the design is the use of reaming nozzles to enlarge a pilot hole. These nozzles eject water upwards along the surface of the nozzle cone, and drill most efficiently when they hang free and unsupported by the sides of the pilot hole. The nozzles incorporate a nozzle-mounted valve, activated when the nozzle cone contacts the ice, thus increasing the back pressure of the water flow. The pressure increase is monitored at the surface and the winch speed is reduced accordingly in order to ensure an efficient drilling operation.

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Siple Coast subglacial aquatic environments: The Whillans Ice Stream Subglacial Access Research Drilling Project

Geophysical Monograph Series - Antarctic Subglacial Aquatic Environments ◽

10.1029/2010gm000932 ◽

2011 ◽

pp. 199-219 ◽

Cited By ~ 20

Author(s):

Helen Amanda Fricker ◽

Ross Powell ◽

John Priscu ◽

Slawek Tulaczyk ◽

Sridhar Anandakrishnan ◽

...

Keyword(s):

Aquatic Environments ◽

Ice Stream ◽

Whillans Ice Stream ◽

Drilling Project

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A microbiologically clean strategy for access to the Whillans Ice Stream subglacial environment

Antarctic Science ◽

10.1017/s0954102013000035 ◽

2013 ◽

Vol 25 (5) ◽

pp. 637-647 ◽

Cited By ~ 34

Author(s):

John C. Priscu ◽

Amanda M. Achberger ◽

Joel E. Cahoon ◽

Brent C. Christner ◽

Robert L. Edwards ◽

...

Keyword(s):

Microbial Contamination ◽

Hot Water ◽

Ice Dynamics ◽

Ross Ice Shelf ◽

Subglacial Environment ◽

West Antarctic ◽

Ice Stream ◽

Whillans Ice Stream ◽

Hydrological System ◽

Drilling Operations

AbstractThe Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project will test the overarching hypothesis that an active hydrological system exists beneath a West Antarctic ice stream that exerts a major control on ice dynamics, and the metabolic and phylogenetic diversity of the microbial community in subglacial water and sediment. WISSARD will explore Subglacial Lake Whillans (SLW, unofficial name) and its outflow toward the grounding line where it is thought to enter the Ross Ice Shelf seawater cavity. Introducing microbial contamination to the subglacial environment during drilling operations could compromise environmental stewardship and the science objectives of the project, consequently we developed a set of tools and procedures to directly address these issues. WISSARD hot water drilling efforts will include a custom water treatment system designed to remove micron and sub-micron sized particles (biotic and abiotic), irradiate the drilling water with germicidal ultraviolet (UV) radiation, and pasteurize the water to reduce the viability of persisting microbial contamination. Our clean access protocols also include methods to reduce microbial contamination on the surfaces of cables/hoses and down-borehole equipment using germicidal UV exposure and chemical disinfection. This paper presents experimental data showing that our protocols will meet expectations established by international agreement between participating Antarctic nations.

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Development of a clean hot water drill to access Subglacial Lake CECs, West Antarctica

Annals of Glaciology ◽

10.1017/aog.2020.88 ◽

2021 ◽

pp. 1-13

Author(s):

Keith Makinson ◽

Paul G. D. Anker ◽

Jonathan Garcés ◽

David J. Goodger ◽

Scott Polfrey ◽

...

Keyword(s):

Code Of Conduct ◽

Hot Water ◽

West Antarctica ◽

West Antarctic Ice Sheet ◽

Subglacial Lake ◽

Subglacial Environment ◽

West Antarctic ◽

Scientific Exploration ◽

Additional Water ◽

Antarctic Research

Abstract Recent drilling successes on Rutford Ice Stream in West Antarctica demonstrate the viability of hot water drilling subglacial access holes to depths >2000 m. Having techniques to access deep subglacial environments reliably paves the way for subglacial lake exploration beneath the thick central West Antarctic Ice Sheet. An ideal candidate lake, overlain by ~2650 m of ice, identified by Centro de Estudios Científicos (CECs), Chile, has led to collaboration with British Antarctic Survey to access Subglacial Lake CECs (SLCECs). To conform with the Scientific Committee on Antarctic Research code of conduct, which provides a guide to responsible scientific exploration and stewardship of these pristine systems, any access drilling must minimise all aspects of contamination and disturbance of the subglacial environment. To meet these challenges, along with thicker ice and 2000 m elevation, pumping and water treatment systems developed for the Subglacial Lake Ellsworth project, together with new diesel generators, additional water heating and longer drill hose, are currently being integrated with the BEAMISH hot water drill. A dedicated test season near SLCECs will commission the new clean hot water drill, with testing and validation of all clean operating procedures. A subsequent season will then access SLCECs cleanly.

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Hot-Water Drilling in the Antarctic Peninsula (Abstract)

Annals of Glaciology ◽

10.3189/s0260305500006777 ◽

1988 ◽

Vol 11 ◽

pp. 215-215

Author(s):

S. Cooper

Keyword(s):

Antarctic Peninsula ◽

Temperature Sensors ◽

Back Pressure ◽

Hot Water ◽

Ice Shelves ◽

Pilot Hole ◽

Fast Ice ◽

Drilling System ◽

The Antarctic ◽

Practical Field

The British Antarctic Survey has developed a hot-water drilling system used chiefly for installing temperature sensors through ice shelves and for retrieving oceanographic equipment tethered through thick fast ice. The specification, design and operation of the drill for these two activities will be discussed and practical field problems will be highlighted.A novel aspect of the design is the use of reaming nozzles to enlarge a pilot hole. These nozzles eject water upwards along the surface of the nozzle cone, and drill most efficiently when they hang free and unsupported by the sides of the pilot hole. The nozzles incorporate a nozzle-mounted valve, activated when the nozzle cone contacts the ice, thus increasing the back pressure of the water flow. The pressure increase is monitored at the surface and the winch speed is reduced accordingly in order to ensure an efficient drilling operation.

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Dynamics of stick–slip motion, Whillans Ice Stream, Antarctica

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2011.02.052 ◽

2011 ◽

Vol 305 (3-4) ◽

pp. 283-289 ◽

Cited By ~ 41

Author(s):

J. Paul Winberry ◽

Sridhar Anandakrishnan ◽

Douglas A. Wiens ◽

Richard B. Alley ◽

Knut Christianson

Keyword(s):

Stick Slip ◽

Ice Stream ◽

Whillans Ice Stream ◽

Stick Slip Motion ◽

Slip Motion

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Isotopic evidence for the origin of dimethylsulfide and dimethylsulfoniopropionate-like compounds in a warm, monomictic freshwater lake

Environmental Chemistry ◽

10.1071/en15042 ◽

2016 ◽

Vol 13 (2) ◽

pp. 340 ◽

Cited By ~ 16

Author(s):

Michal Sela-Adler ◽

Ward Said-Ahmad ◽

Orit Sivan ◽

Werner Eckert ◽

Ronald P. Kiene ◽

...

Keyword(s):

Sulfur Compound ◽

Sulfur Cycle ◽

Freshwater Lake ◽

Aquatic Environments ◽

Dissimilatory Sulfate Reduction ◽

Biogeochemical Processes ◽

Multiple Sources ◽

Isotopic Signatures ◽

Isotopic Evidence ◽

Water Columns

Environmental context The volatile sulfur compound, dimethylsulfide (DMS), plays a major role in the global sulfur cycle by transferring sulfur from aquatic environments to the atmosphere. Compared to marine environments, freshwater environments are under studied with respect to DMS cycling. The goal of this study was to assess the formation pathways of DMS in a freshwater lake using natural stable isotopes of sulfur. Our results provide unique sulfur isotopic evidence for the multiple DMS sources and dynamics that are linked to the various biogeochemical processes that occur in freshwater lake water columns and sediments. Abstract The volatile methylated sulfur compound, dimethylsulfide (DMS), plays a major role in the global sulfur cycle by transferring sulfur from aquatic environments to the atmosphere. The main precursor of DMS in saline environments is dimethylsulfoniopropionate (DMSP), a common osmolyte in algae. The goal of this study was to assess the formation pathways of DMS in the water column and sediments of a monomictic freshwater lake based on seasonal profiles of the concentrations and isotopic signatures of DMS and DMSP. Profiles of DMS in the epilimnion during March and June 2014 in Lake Kinneret showed sulfur isotope (δ34S) values of +15.8±2.0 per mille (‰), which were enriched by up to 4.8 ‰ compared with DMSP δ34S values in the epilimnion at that time. During the stratified period, the δ34S values of DMS in the hypolimnion decreased to –7.0 ‰, close to the δ34S values of coexisting H2S derived from dissimilatory sulfate reduction in the reduced bottom water and sediments. This suggests that H2S was methylated by unknown microbial processes to form DMS. In the hypolimnion during the stratified period DMSP was significantly 34S enriched relative to DMS reflecting its different S source, which was mostly from sulfate assimilation. In the sediments, δ34S values of DMS were depleted by 2–4 ‰ relative to porewater (HCl-extracted) DMSP and enriched relative to H2S. This observation suggests two main formation pathways for DMS in the sediment, one from the degradation of DMSP and one from methylation of H2S. The present study provides isotopic evidence for multiple sources of DMS in stratified water bodies and complex DMSP–DMS dynamics that are linked to the various biogeochemical processes within the sulfur cycle.

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Autonomous Decision-Making While Drilling

Energies ◽

10.3390/en14040969 ◽

2021 ◽

Vol 14 (4) ◽

pp. 969

Author(s):

Eric Cayeux ◽

Benoît Daireaux ◽

Adrian Ambrus ◽

Rodica Mihai ◽

Liv Carlsen

Keyword(s):

Decision Making ◽

Internal State ◽

Drilling Process ◽

Autonomous Decision ◽

Internal States ◽

Markov Decision ◽

Drilling Operations ◽

Drilling System ◽

Drilling Conditions ◽

Erratic Behavior

The drilling process is complex because unexpected situations may occur at any time. Furthermore, the drilling system is extremely long and slender, therefore prone to vibrations and often being dominated by long transient periods. Adding the fact that measurements are not well distributed along the drilling system, with the majority of real-time measurements only available at the top side and having only access to very sparse data from downhole, the drilling process is poorly observed therefore making it difficult to use standard control methods. Therefore, to achieve completely autonomous drilling operations, it is necessary to utilize a method that is capable of estimating the internal state of the drilling system from parsimonious information while being able to make decisions that will keep the operation safe but effective. A solution enabling autonomous decision-making while drilling has been developed. It relies on an optimization of the time to reach the section total depth (TD). The estimated time to reach the section TD is decomposed into the effective time spent in conducting the drilling operation and the likely time lost to solve unexpected drilling events. This optimization problem is solved by using a Markov decision process method. Several example scenarios have been run in a virtual rig environment to test the validity of the concept. It is found that the system is capable to adapt itself to various drilling conditions, as for example being aggressive when the operation runs smoothly and the estimated uncertainty of the internal states is low, but also more cautious when the downhole drilling conditions deteriorate or when observations tend to indicate more erratic behavior, which is often observed prior to a drilling event.

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Modeling Antarctic subglacial lake filling and drainage cycles

The Cryosphere ◽

10.5194/tc-10-1381-2016 ◽

2016 ◽

Vol 10 (4) ◽

pp. 1381-1393 ◽

Cited By ~ 12

Author(s):

Christine F. Dow ◽

Mauro A. Werder ◽

Sophie Nowicki ◽

Ryan T. Walker

Keyword(s):

Internal Controls ◽

Water Volume ◽

Lake Basin ◽

Subglacial Lake ◽

Subglacial Environment ◽

Ice Surface ◽

Ice Stream ◽

Slow Moving ◽

Lake Drainage ◽

Subglacial Lakes

Abstract. The growth and drainage of active subglacial lakes in Antarctica has previously been inferred from analysis of ice surface altimetry data. We use a subglacial hydrology model applied to a synthetic Antarctic ice stream to examine internal controls on the filling and drainage of subglacial lakes. Our model outputs suggest that the highly constricted subglacial environment of our idealized ice stream, combined with relatively high rates of water flow funneled from a large catchment, can combine to create a system exhibiting slow-moving pressure waves. Over a period of years, the accumulation of water in the ice stream onset region results in a buildup of pressure creating temporary channels, which then evacuate the excess water. This increased flux of water beneath the ice stream drives lake growth. As the water body builds up, it steepens the hydraulic gradient out of the overdeepened lake basin and allows greater flux. Eventually this flux is large enough to melt channels that cause the lake to drain. Lake drainage also depends on the internal hydrological development in the wider system and therefore does not directly correspond to a particular water volume or depth. This creates a highly temporally and spatially variable system, which is of interest for assessing the importance of subglacial lakes in ice stream hydrology and dynamics.

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Marine Ice Sheet Instability and Ice Shelf Buttressing Influenced Deglaciation of the Minch Ice Stream, Northwest Scotland

10.5194/tc-2018-116 ◽

2018 ◽

Cited By ~ 1

Author(s):

Niall Gandy ◽

Lauren J. Gregoire ◽

Jeremy C. Ely ◽

Christopher D. Clark ◽

David M. Hodgson ◽

...

Keyword(s):

Ice Sheets ◽

Ice Sheet ◽

Last Deglaciation ◽

Ice Shelf ◽

Dynamical Processes ◽

Ice Dynamics ◽

Surface Mass ◽

Ice Shelves ◽

Ice Stream ◽

The Last Deglaciation

Abstract. Uncertainties in future sea level projections are dominated by our limited understanding of the dynamical processes that control instabilities of marine ice sheets. A valuable case to examine these processes is the last deglaciation of the British-Irish Ice Sheet. The Minch Ice Stream, which drained a large proportion of ice from the northwest sector of the British-Irish Ice Sheet during the last deglaciation, is well constrained, with abundant empirical data which could be used to inform, validate and analyse numerical ice sheet simulations. We use BISICLES, a higher-order ice sheet model, to examine the dynamical processes that controlled the retreat of the Minch Ice Stream. We simulate retreat from the shelf edge under constant "warm" surface mass balance and subshelf melt, to isolate the role of internal ice dynamics from external forcings. The model simulates a slowdown of retreat as the ice stream becomes laterally confined at a "pinning-point" between mainland Scotland and the Isle of Lewis. At this stage, the presence of ice shelves became a major control on deglaciation, providing buttressing to upstream ice. Subsequently, the presence of a reverse slope inside the Minch Strait produces an acceleration in retreat, leading to a "collapsed" state, even when the climate returns to the initial "cold" conditions. Our simulations demonstrate the importance of the Marine Ice Sheet Instability and ice shelf buttressing during the deglaciation of parts of the British-Irish Ice Sheet. Thus, geological data could be used to constrain these processes in ice sheet models used for projecting the future of our contemporary ice sheets.

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