Does subglacial water exist

An experimental, hypothetical discovery of a subglacial lake under the ice sheet below Vostok Station was accomplished in 1964, and later inferred when direct contact with liquid water was made in 1968 under the ice sheet below Byrd Station.

Very important measurements for understanding the glaciology of the ice sheet in the vicinity of Vostok Station were accomplished by Dr. Kapitsa in 1959 when he conducted the first seismic study of the area using a new technique. On the basis of his previous experience of seismic sounding in Antarctica he found that placing geophones close to the snow surface on the ice sheet was a source of possible errors when it came to interpreting reflected signals due to background noise on the seismograms. To reduce the noise he placed the geophones as deep as possible into the ice sheet, some as deep as 40 m. A special rig for drilling holes for geophones was transported by sledge and tractor to Vostok Station, this led to a significant improvement in the seismograms. Kapitsa (1961) showed in 1958 that the thickness of the ice sheet at Vostok Station was about 3,700 m, not 2,000 m as previously believed. Figure 3.1 is a photograph of Dr. Kapitsa at the time he undertook these soundings.

In a second seismic study of the ice thickness at Vostok Station in 1963, Dr. Kapitsa recorded two reflections from the bottom area. He interpreted the upper reflection as the lower boundary of ice, at a depth of 3,750 m, and the lower one as the lower boundary of a frozen sedimentary layer (Kapitsa, 1968).

It took 30 years for the scientific world to learn that the space between these two reflections was water - Lake Vostok. Until that time the seismogram was never published or made available for study by other scientists. The seismogram was reinterpreted on the occasion of the first International Workshop on the Study of Lake Vostok in 1994 and the upper reflection was identified as the ice/water boundary, the "sediment layer" was identified as the 500-m water layer that is now known as Lake Vostok. This seismogram and the discovery of the thick water layer below the ice sheet at Vostok Station ware presented by Dr. Kapitsa

Figure 3.1. Dr. Kapitsa at the time he worked on reinterpretation of his seismograms, taken at Vostok Station.

at the Scientific Committee on Antarctic Research (SCAR) meeting in Rome in 1994. It was accepted by its delegates with great enthusiasm and was published in 1996 (Kapitsa et al., 1996). The seismogram is shown at Figure 3.2.

I am surprised that neither Dr. Kapitsa nor I attempted to relate this second bottom reflection to the concept of a subglacial lake. We both thought about it, and skirted around the subject at the time, but did not pursue it. Our collaborative work and discussions about a permanent melting at the bottom of the ice sheet below Vostok Station, and the possibility of the existence of a subglacial lake were already published.

In 1963, Dr. Kapitsa and I proposed a project for a Sub-glacial Autonomous Station (SGAS, or PLAS in Russian), for the penetration of the Antarctic Ice Sheet to study the bottom water layer and the possible subglacial lake. The project was based on a small nuclear power plant that would be lowered, as part of a hermetically sealed container of the SGAS, which would contain appropriate instruments and equipment. The nuclear power plant had to produce enough energy to melt the SGAS down to the bottom of the ice sheet. No hole was needed, as the SGAS would sink in a water cavern as the ice melted below it, and the resulting meltwater would refreeze above it. Communication with the ice sheet surface would be maintained by wireless means. This project was approved by the Atomic Energy Institute (now Kurchatov's Institute) of the U.S.S.R. Academy of Sciences at a special meeting, in which the Institute agreed to provide a small nuclear energy reactor of 100 kW, small enough to be installed in the SGAS's 0.9 m diameter cylindrical container. However, this project was never realized. We made the mistake at the beginning

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Figure 3.2. Seismogram taken by A. P. Kapitsa at Vostok Station in 1964, reinterpreted by him in 1993 and presented to the SCAR meeting in 1994 (adapted from Kapitsa et ai, 1996). This figure represents a section of a 24-channel seismic record with two bottom reflections. The space between the "first reflection" and "second reflection" was interpreted in 1965 as a sedimentary layer (Kapitsa, 1968) - a view accepted until 1993. In 1994 the first reflection of this figure was reinterpreted as an ice-water interface (Kapitsa et al., 1996). The figure records movement over a vertical line of seismometers from 49 m to 2.5 m depth in a borehole situated 180 m from an explosion. It covers the period from 1.85-2.9 s after the explosion of a 5 kg charge of TNT at a depth of 39 m. A conventional horizontal spread of 12 seismometers at 20-m intervals recorded the same echoes, these are not shown. The echo from the bottom of the ice sheet, which is interpreted as an ice-water interface reaches the deepest (49 m) seismometer first at approximately 1.91 s. It then travels up the seismometer line to the surface where it is reflected down to pass the 49-m seismometer approximately 50 ms later. This has a mean velocity of about 2,200 m s_1, typical of compression (P) waves in the top 50 m of firn in this region. About 45 ms after the first arrival, a second wave train of similar intensity and duration follows as result of initial surface reflection of the explosion at 39 m depth. There is no significant return of energy between approximately 2.00 and 2.63 s, when a weaker wave train passes up and down the seismometer line at the same velocity. This confirms that they are compressive (P) waves, the only waves that travel through water, and not transverse (PS) waves, which are sometimes recorded from shots on ice shelves (Kapitsa et al, 1996).

of planning to remain a strictly national project and as such classified (because the nuclear energy reactor was classified). The SGAS was never built. In a comparable example, Philberth (1974) devised a thermoprobe, with an energy supply located at the surface, that melted its way downward through the ice, with the melted water refreezing above the probe. One element that prevented this experiment ever being realized was the nuclear-powered device - something that in the 1960s raised concerns. Additionally, we did not know how to retrieve the SGAS to the surface of the ice sheet. We could not abandon it because the Antarctic Treaty prohibited the disposal of radioactive waste or nuclear power plants in Antarctica. Nevertheless, writing the proposal showed that we were giving serious thought to the existence of a lake below the ice sheet. The lake remained undiscovered for the time being.

The idea of the use of nuclear power to penetrate the ice was discussed again a few years ago. The problem of bringing the SGAS back to surface was solved, at least theoretically: the SGAS was to be designed to float in water - it would be inverted with its hot side up so that it would melt the refrozen ice on the way back up to the surface (Zotikov, 1993).

This idea received new discussion in 1994, after the first Cambridge workshop of 1993, when it became clear that a large subglacial lake below Vostok Station did exist. The same Atomic Energy Institute (now Kurchatov's Institute) agreed to my suggestion for the design of a new and different unit. The institute suggested a unit powered by a nuclear thermoelectric plant that would produce 0.5-2 MW of heat and 10 kW of electricity, with a capability to continue at that level for many years in an environment such as that of Lake Vostok.

However, the general attitude for the use of nuclear energy in the form of a power plant changed, thus making it unlikely that a plant of this type would be acceptable for this application. On the other hand, the concept could be used for making an SGAS device for the study of a subglacial ocean on Europa (a moon of Jupiter), or perhaps the subglacial lakes of Mars (the NASA Cryobot concept). However, it is likely that the idea of using nuclear power to penetrate the ice cover of Europa would meet with strong opposition from environmentalist groups because the nuclear-power device for drilling would first need to be launched into space from Earth.

Returning to the mid-1960s, I spent my second overwinter in Antarctica at McMurdo Station in 1965 as a Russian exchange scientist in the U.S. Antarctic Program. As a result of trying to make a homemade drill to produce a hole at the edge of the Ross Ice Shelf, near McMurdo, I had close contact with the drilling team of the U.S. Army Cold Regions Research and Engineering Laboratory. They had the best drilling equipment in the world at that time, and were intending to drill to the bottom of the ice sheet at Byrd Station to collect ice cores and measure the ice temperature and so on. The thickness of the ice sheet there is more than 2,000 m, and the station is located over the area of bottom melting on my map. We discussed this subject, but I had a feeling they did not take the suggestion of bottom melting seriously.

Two more years elapsed, and on 2 February 1967 a large 87 ft (29 m) long electrothermal drill was installed at Byrd Station to start its objective of reaching

Figure 3.3. American electrical drill unit at Byrd Station (adapted from Ueda and Garfield, 1969). In 1968 this unit at Byrd Station penetrated 2,000 m of ice sheet reaching the bottom and encountering liquid water.

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Figure 3.3. American electrical drill unit at Byrd Station (adapted from Ueda and Garfield, 1969). In 1968 this unit at Byrd Station penetrated 2,000 m of ice sheet reaching the bottom and encountering liquid water.

the bottom of the ice sheet - this was the first attempt in Antarctica to reach the bottom of its central region. Figure 3.3 gives some details of this drilling program. A report by Ueda and Garfield (1969) began:

On 29 January 1968 a USA CRREL drilling team successfully penetrated the Antarctic Ice Sheet at Byrd Station after drilling through 7,100 ft (2,367 m) of ice.

These words were written proudly in the introduction to the report, which went on to describe the problems they encountered whilst drilling. Most of the drilling was accomplished with a cable-suspended electro-mechanical, rotary coring Electrodrill purchased by CRREL from Reda Pump Co., Bartlesville, Oklahoma in 1964. It was invented by the head of the company, Mr. Armais Arutunoff, an oil exploration engineer. After being modified and tested for coring in ice, it was used to penetrate the Greenland Ice Sheet at Camp Century in 1966 (Ueda and Garfield, 1968, 1969). After further modification, it was used during the 1966-1967 and 1967-1968 austral summers at Byrd Station.

It is interesting to note that in the drilling report for Byrd Station, "The primary objectives of the drilling were given: (1) to cut a hole completely through the ice sheet to allow measurements of the temperature profile, the ice flow within the ice sheet, and the ice flow relative to the underlying bed; (2) to provide a continuous, undisturbed core for investigating the physical, structural, and geochemical properties of the ice; and (3) to permit the future in situ extraction of entrapped atmospheric gases such as the carbon dioxide used to age date the ice" (Ueda and Garfield, 1969).

There was nothing mentioned in the primary objectives about the possibility (or interest or danger) of encountering liquid water at the base of the ice sheet. The report does, however, mention the incident of encountering water at the base, the original wording of the report being:

On 28 January 1968, at a vertical depth of 7,082ft (2,360.7 m), the first indication of sub-ice debris was recorded ... On the following run, at a depth of 7,101 ft (2,367 m), a sudden decrease in power and a corresponding increase in cable tension was noted, indicating an abrupt change in material had been encountered by the cutting bit. This was later concluded to be, after analyses of subsequent events, a layer of water estimated by the authors to be less than a foot thick. After a few minutes the power increased and drilling was continued to a depth of 7,105 ft (2,368 m). A total of 7.5ft (2.5 m) of core containing more rock and soil debris was frozen into the upper part of the core barrel. No sub-ice core was recovered.

By the time of the next run, which was several hours later due to equipment repairs, it was noted that the fluid in the hole had risen from 630ft (210 m) to 313 ft. (104.3 m) from the surface. The glycol column down-hole had risen from 5,743ft (1,914m) to 5,557ft (1,852m) ...

Some 30 years after this dramatic event, I was drilling a hole in 1977 through 416 m of the Ross Ice Shelf. I encountered a water level, just a few meters before the subglacial ocean water, and experienced events comparable with the drilling at Byrd Station (Zotikov, 1979), indicating that subglacial water had been reached and that the rising liquid level meant that the water would soon encounter the upper, cooler parts of the hole and freeze. Therefore, the message was clear - all equipment must be removed before it became frozen in the hole and therefore damaged, and probably irretrievable. It is easy in hindsight to realize what happened after 30 years of work in this field. In the last days of January 1968 during the drilling project at Byrd Station, further comments from the report are worth repeating:

... Various drill surfaces were showing signs of rusting, a phenomenon never noted previously. The only visible evidence of the nature of the sub-ice material were thin films of clay on the drill surfaces ...

... The effects of the down-hole water caught in the drill sections which had subsequently frozen during the trip out of the hole began to have serious consequences ... Damage to parts of the drill from the high freezing forces created additional problems and delays. For fear of [...] the loss of the drill, attempts to obtain a sub-ice sample were terminated on 2 February 1968.

By coincidence, in the beginning of 1968 I completed a draft of my DSc. thesis (Zotikov, 1968), and the permanent bottom melting in the central part of the Antarctic Ice Sheet was one of its main topics. The scheduled day of the defense of my thesis (in Russia we use this term instead of "examination", as in France) before the Scientific Council of Arctic and Antarctic Research Institute in Leningrad was announced as 11 June 1968 - a very important day for me. There were to be many scientists present who did not believe in warm bottom ice and liquid water at the bottom of the central part of the Antarctic Ice Sheet, and I received negative reviews from two leading glaciologists in my country on this matter, which was the main topic of the dissertation. It was mentioned to me that agreement with my idea by the Scientific Council of the Arctic and Antarctic Research Institute was questionable.

Shortly before the date of my "examination", I received an important and timely message from my friends in the U.S. Antarctic drilling team. They informed me that they reached the bottom of the ice sheet at Byrd Station, and unexpectedly had found water.

I saved this telegram for the day of the defense and at the appropriate time the Secretary of the Scientific Council read it. Perhaps because of that everyone in the council voted unanimously in favor of my thesis. Unexpectedly, the uncertainty of the scientific community was so high that it took another two years for the Highest Attestation Committee of the U.S.S.R. to approve the decision of the Scientific Council.

Regarding the drilling operation at Byrd Station, it should be mentioned that very little of the drill could be recovered making it difficult to proceed further with the experiment - so the operation was closed down completely. The manufacturers of the equipment did not get an extended contract, so the experience, skill, and momentum of the best ice cap drilling program in the world was lost.

It took the U.S. Antarctic Program nearly 15 years to recover and catch up with international levels of deep-ice drilling.

I seldom read anything that mentioned the possible existence of liquid water below the ice sheet under Byrd Station; similarly the literature did not contain information about the necessary precautions required to prevent water from getting into and rising up the drilling hole. For example the increase in the height of a column of unfrozen drilling fluid, which was put into the hole to compensate for the Mountain Pressure1 and prevent hole closure, could prevent the sequence of events that would close the hole and freeze around the drilling equipment. In addition, no one anticipated the possibility of organisms in the water until 20 years later.

1 The Mountain Pressure at any depth is jargon from Russian mining engineers, meaning the hydrostatic pressure equal to that of a column of rock (or ice, in this case) above this depth.

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