scholarly journals WISSARD at Subglacial Lake Whillans, West Antarctica: scientific operations and initial observations

2014 ◽  
Vol 55 (65) ◽  
pp. 51-58 ◽  
Author(s):  
Slawek Tulaczyk ◽  
Jill A. Mikucki ◽  
Matthew R. Siegfried ◽  
John C. Priscu ◽  
C. Grace Barcheck ◽  
...  
Keyword(s):  
Sea Water ◽  
Freezing Point ◽  
Water Pressure ◽  
Sediment Cores ◽  
Water Reservoir ◽  
Hot Water ◽  
Subglacial Lake ◽  
Lake Bottom ◽  
Filtration Unit ◽  
Subglacial Lake Whillans

AbstractA clean hot-water drill was used to gain access to Subglacial Lake Whillans (SLW) in late January 2013 as part of the Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project. Over 3 days, we deployed an array of scientific tools through the SLW borehole: a downhole camera, a conductivity–temperature–depth (CTD) probe, a Niskin water sampler, an in situ filtration unit, three different sediment corers, a geothermal probe and a geophysical sensor string. Our observations confirm the existence of a subglacial water reservoir whose presence was previously inferred from satellite altimetry and surface geophysics. Subglacial water is about two orders of magnitude less saline than sea water (0.37–0.41 psu vs 35 psu) and two orders of magnitude more saline than pure drill meltwater (<0.002 psu). It reaches a minimum temperature of –0.55~C, consistent with depression of the freezing point by 7.019 MPa of water pressure. Subglacial water was turbid and remained turbid following filtration through 0.45 µm filters. The recovered sediment cores, which sampled down to 0.8 m below the lake bottom, contained a macroscopically structureless diamicton with shear strength between 2 and 6 kPa. Our main operational recommendation for future subglacial access through water-filled boreholes is to supply enough heat to the top of the borehole to keep it from freezing.

scholarly journals Thermal Regime of George VI Ice Shelf, Antarctic Peninsula (Abstract)

1988 ◽  
Vol 11 ◽  
pp. 206 ◽  
Author(s):  
J. G. Paren ◽  
S. Cooper
Keyword(s):  
Sea Level ◽  
Thermal Regime ◽  
Sea Water ◽  
Water Movement ◽  
Freezing Point ◽  
Flow Line ◽  
Layer Structure ◽  
Hot Water ◽  
Lake Area ◽  
Ice Shelf

New data on the thermal regime of George VI Ice Shelf have been obtained by thermistor chains installed through the use of a hot-water drill. Twenty thermistors are used at each site, spaced close together at sea-level and at the base of the ice shelf, and farther apart elsewhere in the ice shelf and in the sea beneath. Based on earlier observations (Bishop and Walton 1981, fig. 7) that the 10 m temperature warms from around −10°C in the central melt-lake area of the ice shelf (from 70°45′ to 71°45′S) to around −2°C near the northern ice front (70°00′S), the thermistor chains were deployed at three sites (70°00′, 70°15′ and 70°30′S) along a presumed flow line. The observations show that as ice flows towards the northern ice front of George VI Ice Shelf, it becomes more temperate in character. Heat from the sea and from the percolation of melt water at the upper surface progressively warms the ice shelf. At mid-depth (the coldest level in the ice shelf) the recorded temperatures were −6°C off Moore Point (70°30′S), −4°C off Carse Point (70°15′S) and, near the northern ice front (70°00′S), between −1.6° and −1.8°C depending on the time of year. The ice-shelf temperatures near the ice front, warmer in mid-summer than the freezing point of fully saline sea-water, are most unusual. The only explanation of the high, fluctuating temperatures found 1 year after drilling is that the hole through the ice shelf was open, allowing unimpeded water movement. This implies that the ice shelf is also warmed by the percolation of sea-water, whose presence was confirmed by ice-core drilling to below sea-level. Confirmation of the presence of brine below sea-level in the ice shelf comes from geo-electrical investigations. A Schlumberger georesistivity array modelled the ice shelf as a simple two-layer structure, with ordinary glacier overlying highly conductive ice. This is consistent with the fact that no radio echoes have been received from the bottom of George VI Ice Shelf to the north of 70°09′S. A detailed analysis of the ice-shelf / ocean-temperature profiles was undertaken. This included an analysis of the fluctuation observed in mid-summer at the warmest site and the subsequent transition to a stable isothermal profile through the submerged part of the ice shelf.

scholarly journals The BAS ice-shelf hot-water drill: design, methods and tools

2014 ◽  
Vol 55 (68) ◽  
pp. 44-52 ◽  
Author(s):  
Keith Makinson ◽  
Paul G.D. Anker
Keyword(s):  
Modular Design ◽  
Sea Water ◽  
Sediment Cores ◽  
Hot Water ◽  
Ice Shelf ◽  
Water Conductivity ◽  
Ice Shelves ◽  
Field Season ◽  
Temperature Depth

AbstractThe 2011/12 Antarctic field season saw the first use of a new British Antarctic Survey (BAS) ice-shelf hot-water drill system on the Larsen C and George VI ice shelves. Delivering 90 L min−1 at 80°C, a total of five holes >30 cm in diameter at three locations were successfully drilled through almost 400 m of ice to provide access to the underlying ocean, including the first access beneath the Larsen C ice shelf. These access holes enabled the deployment of instruments to measure sea-water conductivity, temperature, depth and microstructure, the collection of water samples and up to 2.9 m long sediment cores, before long-term oceanographic moorings were deployed. The simple modular design allowed for Twin Otter aircraft deployment, rapid assembly and commissioning of the system, which proved highly reliable with minimal supervision. A number of novel solutions to various operational sub-ice-shelf profiling and mooring deployment issues were successfully employed through the hot-water drilled access holes to aid the positioning, recovery and deployment of instruments. With future activities now focusing on the Filchner–Ronne Ice Shelf, the drill has been upgraded from its current 500 m capability to 1000 m with additional drill hose and further generator, pumping and heating modules.

scholarly journals Enabling clean access into Subglacial Lake Whillans: development and use of the WISSARD hot water drill system

2016 ◽  
Vol 374 (2059) ◽  
pp. 20140305 ◽  
Author(s):  
Frank R. Rack
Keyword(s):  
Hot Water ◽  
Ice Shelf ◽  
West Antarctic Ice Sheet ◽  
Subglacial Lake ◽  
West Antarctic ◽  
Science Management ◽  
University Of Nebraska Lincoln ◽  
Subglacial Lakes ◽  
The University ◽  
Subglacial Lake Whillans

Clean hot water drill systems (CHWDSs) are used with clean access protocols for the exploration of subglacial lakes and other subglacial aquatic environments (e.g. ice-shelf cavities) in Antarctica. A CHWDS developed for the Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project by the Science Management Office at the University of Nebraska-Lincoln (UNL-SMO), USA, was specifically designed for use in West Antarctica, where the US Antarctic Program's South Pole Traverse could assist with logistical support. The initial goal was to provide clean access holes through ice up to 1000 m thick following environmental stewardship guidelines; however, the existing design allows this CHWDS to be used for ice thicknesses up to 2000 m following modifications to accommodate longer hose lengths. In January 2013, the WISSARD CHWDS successfully provided for the first time a clean access borehole through 800 m of ice into Subglacial Lake Whillans beneath the West Antarctic Ice Sheet for the deployment of scientific instruments and sampling tools. The development and initial use of the WISSARD CHWDS required the project team to address a number of constraints while providing contingencies to meet the defined project scope, schedule and budget.

scholarly journals Thermal Regime of George VI Ice Shelf, Antarctic Peninsula (Abstract)

1988 ◽  
Vol 11 ◽  
pp. 206-206
Author(s):  
J. G. Paren ◽  
S. Cooper
Keyword(s):  
Sea Level ◽  
Thermal Regime ◽  
Sea Water ◽  
Water Movement ◽  
Freezing Point ◽  
Flow Line ◽  
Layer Structure ◽  
Hot Water ◽  
Lake Area ◽  
Ice Shelf

New data on the thermal regime of George VI Ice Shelf have been obtained by thermistor chains installed through the use of a hot-water drill. Twenty thermistors are used at each site, spaced close together at sea-level and at the base of the ice shelf, and farther apart elsewhere in the ice shelf and in the sea beneath. Based on earlier observations (Bishop and Walton 1981, fig. 7) that the 10 m temperature warms from around −10°C in the central melt-lake area of the ice shelf (from 70°45′ to 71°45′S) to around −2°C near the northern ice front (70°00′S), the thermistor chains were deployed at three sites (70°00′, 70°15′ and 70°30′S) along a presumed flow line.The observations show that as ice flows towards the northern ice front of George VI Ice Shelf, it becomes more temperate in character. Heat from the sea and from the percolation of melt water at the upper surface progressively warms the ice shelf. At mid-depth (the coldest level in the ice shelf) the recorded temperatures were −6°C off Moore Point (70°30′S), −4°C off Carse Point (70°15′S) and, near the northern ice front (70°00′S), between −1.6° and −1.8°C depending on the time of year.The ice-shelf temperatures near the ice front, warmer in mid-summer than the freezing point of fully saline sea-water, are most unusual. The only explanation of the high, fluctuating temperatures found 1 year after drilling is that the hole through the ice shelf was open, allowing unimpeded water movement. This implies that the ice shelf is also warmed by the percolation of sea-water, whose presence was confirmed by ice-core drilling to below sea-level. Confirmation of the presence of brine below sea-level in the ice shelf comes from geo-electrical investigations. A Schlumberger georesistivity array modelled the ice shelf as a simple two-layer structure, with ordinary glacier overlying highly conductive ice. This is consistent with the fact that no radio echoes have been received from the bottom of George VI Ice Shelf to the north of 70°09′S.A detailed analysis of the ice-shelf / ocean-temperature profiles was undertaken. This included an analysis of the fluctuation observed in mid-summer at the warmest site and the subsequent transition to a stable isothermal profile through the submerged part of the ice shelf.

scholarly journals Physical processes in Subglacial Lake Whillans, West Antarctica: Inferences from sediment cores

2016 ◽  
Vol 444 ◽  
pp. 56-63 ◽  
Author(s):  
T.O. Hodson ◽  
R.D. Powell ◽  
S.A. Brachfeld ◽  
S. Tulaczyk ◽  
R.P. Scherer
Keyword(s):  
Sediment Cores ◽  
West Antarctica ◽  
Physical Processes ◽  
Subglacial Lake ◽  
Subglacial Lake Whillans

scholarly journals Probe technologies for clean sampling and measurement of subglacial lakes

2016 ◽  
Vol 374 (2059) ◽  
pp. 20150267 ◽  
Author(s):  
Matt Mowlem ◽  
Kevin Saw ◽  
Robin Brown ◽  
Edward Waugh ◽  
Christopher L. Cardwell ◽  
...  
Keyword(s):  
Lessons Learned ◽  
Hot Water ◽  
Lake Vostok ◽  
Subglacial Lake ◽  
Field Season ◽  
Electrical Conducting ◽  
Subglacial Lakes ◽  
Subglacial Lake Whillans ◽  
Negatively Buoyant ◽  
Sediment Corer

It is 4 years since the subglacial lake community published its plans for accessing, sampling, measuring and studying the pristine, and hitherto enigmatic and very different, Antarctic subglacial lakes, Vostok, Whillans and Ellsworth. This paper summarizes the contrasting probe technologies designed for each of these subglacial environments and briefly updates how these designs changed or were used differently when compared to previously published plans. A detailed update on the final engineering design and technical aspects of the probe for Subglacial Lake Ellsworth is presented. This probe is designed for clean access, is negatively buoyant (350 kg), 5.2 m long, 200 mm in diameter, approximately cylindrical and consists of five major units: (i) an upper power and communications unit attached to an optical and electrical conducting tether, (ii)–(iv) three water and particle samplers, and (v) a sensors, imaging and instrumentation pack tipped with a miniature sediment corer. To date, only in Subglacial Lake Whillans have instruments been successfully deployed. Probe technologies for Subglacial Lake Vostok (2014/15) and Lake Ellsworth (2012/13) were not deployed for technical reasons, in the case of Lake Ellsworth because hot-water drilling was unable to access the lake during the field season window. Lessons learned and opportunities for probe technologies in future subglacial access missions are discussed.

scholarly journals Developing a hot-water drill system for the WISSARD project: 1. Basic drill system components and design

2014 ◽  
Vol 55 (68) ◽  
pp. 285-297 ◽  
Author(s):  
Frank R. Rack ◽  
Dennis Duling ◽  
Daren Blythe ◽  
Justin Burnett ◽  
Dar Gibson ◽  
...  
Keyword(s):  
Hot Water ◽  
West Antarctica ◽  
Initial Field ◽  
Subglacial Lake ◽  
Basal Ice ◽  
Science Management ◽  
Field Season ◽  
University Of Nebraska Lincoln ◽  
Subglacial Lake Whillans ◽  
Drill System

AbstractA new, clean, hot-water drill system (HWDS) was developed by the Science Management Office, University of Nebraska-Lincoln, for use in the Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project to gain access to Subglacial Lake Whillans beneath ∼800 m of ice in West Antarctica. One primary borehole was drilled into the basal ice environment of Subglacial Lake Whillans during the initial field season in 2012/13. This paper describes the process of designing, fabricating, assembling, shipping, testing, commissioning and traversing the WISSARD HWDS leading up to the first scientific use of the system.

scholarly journals Scientific access into Mercer Subglacial Lake: scientific objectives, drilling operations and initial observations

2021 ◽  
pp. 1-13
Author(s):  
John C. Priscu ◽  
Jonas Kalin ◽  
John Winans ◽  
Timothy Campbell ◽  
Matthew R. Siegfried ◽  
...  
Keyword(s):  
Lake Sediments ◽  
Water Column ◽  
Lake Water ◽  
Sediment Cores ◽  
Hot Water ◽  
Water Ice ◽  
Subglacial Lake ◽  
Entry Models ◽  
Borehole Water ◽  
Ice Water

Abstract The Subglacial Antarctic Lakes Scientific Access (SALSA) Project accessed Mercer Subglacial Lake using environmentally clean hot-water drilling to examine interactions among ice, water, sediment, rock, microbes and carbon reservoirs within the lake water column and underlying sediments. A ~0.4 m diameter borehole was melted through 1087 m of ice and maintained over ~10 days, allowing observation of ice properties and collection of water and sediment with various tools. Over this period, SALSA collected: 60 L of lake water and 10 L of deep borehole water; microbes >0.2 μm in diameter from in situ filtration of ~100 L of lake water; 10 multicores 0.32–0.49 m long; 1.0 and 1.76 m long gravity cores; three conductivity–temperature–depth profiles of borehole and lake water; five discrete depth current meter measurements in the lake and images of ice, the lake water–ice interface and lake sediments. Temperature and conductivity data showed the hydrodynamic character of water mixing between the borehole and lake after entry. Models simulating melting of the ~6 m thick basal accreted ice layer imply that debris fall-out through the ~15 m water column to the lake sediments from borehole melting had little effect on the stratigraphy of surficial sediment cores.

The Effects of Salinity on Herring After Metamorphosis

1961 ◽  
Vol 41 (1) ◽  
pp. 37-48 ◽  
Author(s):  
F. G. T. Holliday ◽  
J. H. S. Blaxter
Keyword(s):  
Salinity Tolerance ◽  
Blood Concentration ◽  
Sea Water ◽  
Freezing Point ◽  
Tolerance Range ◽  
Blood Concentrations

The salinity tolerance of herring 9-ca 24 cm in length was found to lie between 6‰0 and 40–45‰0.Determinations of changes in weight and blood concentration (by measurement of the freezing-point), when herring were transferred from one salinity to another, demonstrated that extensive changes occurred in the blood. Under these conditions the herring experienced and survived blood concentrations equivalent to salinites of 13–22·5‰. A recovery to near normal (δ0·95 ≡ 15·8‰) took place in all the salinities within the tolerance range.Badly descaled herring in sea water showed large increases in blood concentration before death.A study of the kidney of the herring indicated that the ability to withstand the low salinities for long periods probably rested in the high glomerular count of the kidney.The importance of damage to the skin for survival is discussed in relation to tagging experiments.The results are also discussed in relation to the evolution of the herring.

The ice nucleating ability of macromolecules in immersion freezing decreases in the presence of salts: Implications for freezing point depression calculations

2021 ◽  
Author(s):  
Jon F. Went ◽  
Jeanette D. Wheeler ◽  
François J. Peaudecerf ◽  
Nadine Borduas-Dedekind
Keyword(s):  
Sea Water ◽  
Freezing Point ◽  
Pure Water ◽  
Salt Content ◽  
Mixed Phase ◽  
Cloud Formation ◽  
Sea Spray ◽  
Freezing Point Depression ◽  
Immersion Freezing ◽  
Mixed Phase Clouds

&lt;p&gt;Cloud formation represents a large uncertainty in current climate predictions. In particular, ice in mixed-phase clouds requires the presence of ice nucleating particles (INPs) or ice nucleating macromolecules (INMs). An influential population of INPs has been proposed to be organic sea spray aerosols in otherwise pristine ocean air. However, the interactions between INMs present in sea water and their freezing behavior under atmospheric immersion freezing conditions warrants further research to constrain the role of sea spray aerosols on cloud formation. Indeed, salt is known to lower the freezing temperature of water, through a process called freezing point depression (FPD). Yet, current FPD corrections are solely based on the salt content and assume that the INMs&amp;#8217; ice nucleation abilities are identical with and without salt. Thus, we measured the effect of salt content on the ice nucleating ability of INMs, known to be associated with marine phytoplankton, in immersion freezing experiments in the Freezing Ice Nuclei Counter (FINC) (Miller et al., AMTD, 2020). We measured eight INMs, namely taurine, isethionate, xylose, mannitol, dextran, laminarin, and xanthan as INMs in pure water at temperatures relevant for mixed-phase clouds (e.g. 50% activated fraction at temperatures above &amp;#8211;23 &amp;#176;C at 10 mM concentration). Subsequently, INMs were analyzed in artificial sea water containing 36 g salt L&lt;sup&gt;-1&lt;/sup&gt;. Most INMs, except laminarin and xanthan, showed a loss of ice activity in artificial sea water compared to pure water, even after FPD correction. Based on our results, we hypothesize sea salt has an inhibitory effect on the ice activity of INMs. This effect influences our understanding of how INMs nucleate ice as well as challenges our use of FPD correction and subsequent extrapolation to ice activity under mixed-phase cloud conditions.&lt;/p&gt;

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