“Subglacial Lake Exploration:
Workshop Report and Recommendations”
Scientific Committee on Antarctic Research
in regard to the
SCAR International Workshop on Subglacial Lake Exploration
TABLE OF CONTENTS
ACKNOWLEDGMENTS ................................................................................... iii
EXECUTIVE SUMMARY.................................................................................. iv
SECTION I - THE SCIENCE PLAN - LIFE UNDER THE ICE AND THE
EVOLUTION OF ANTARCTICA............................................. 1
Scientific Objectives ................................................................................. 2
Exploration Technologies ........................................................................ 8
Stages of Exploration ............................................................................... 9
Recommendations .................................................................................... 11
SECTION II - STATE OF THE KNOWLEDGE OF SUBGLACIAL
Introduction .............................................................................................. 12
Subglacial Lake Conceptual Model ........................................................ 14
Life Under the Ice..................................................................................... 16
Climatic and Tectonic Evolution of Antarctica..................................... 22
An Extraterrestrial Analogue ................................................................. 24
Lake Vostok: To Drill or Not to Drill? R. Roura
Does UV Radiation Close the Global Carbon Cycle? - A Maurice A. Lock
Test in Lake Vostok
The Potentials for Cosmogenic Be10 and Inorganic Particles Ala Aldahan
in Deciphering Environmental History of Lake Vostok
Recognition of Biomolecules, Past and Present, in Lake David D. Wynn-Williams
Sediments of Lake Vostok by Remote Sensing
Searching for Microbial Sub-Fossils-Enrichment Culture B.J. Finlay and K.J. Clarke
and Electron Microscopy
Micron - Scale Structure of Trace Metals in Pore Waters: Gary Rones, Bill Davison, and
A Possible Technique for Investigating Sub-Glacial Lakes Geoff Grime
Metal Mobilisation in the Surface cm’s of Marine Gary Fones, Bill Davison, and
Sediments using DGT John Hamilton-Taylor
How Old is Lake Vostok? Peter Barrett
Food Webs in Lake Vostok? Hypotheses About a Hidden Roland Psenner and Birgit
Ice coring in the Context of Antarctic Subglacial Lake Jean Robert Petit
Food Webs and Ecosystem Evolution in Lake Vostok Roland Psenner and Birgit
LIST OF PARTICIPANTS
The workshop on subglacial lakes held in Cambridge during September 1999 was a result
of generous financial support provided by the British Antarctic Survey, the Scientific Committee
for Antarctic Research (SCAR), the National Science Foundation (NSF), the European Science
Foundation (ESF), the British Council and the US National Aeronautic and Space
Administration’s (NASA) Astrobiology Program.
The meeting was convened at the request of the SCAR Executive and its President,
Professor Robert Rutford. Dr. Peter Clarkson (SCAR Secretariat; www.scar.org) provided an
extremely helpful link to the Executive. The meeting benefited greatly from the enthusiastic
support and experience of the Workshop Advisory Committee - Prof. Heinz Miller (Germany,
chair), Dr. Martin Melles (Germany), Dr. Jean Robert Petit (France), Dr. Robin Bell (USA),
Prof. Jim Tiedje (USA) and Dr. Mahlon C. Kennicutt II (USA). We would also like to thank the
additional contributors to the NASA-sponsored post-workshop writing/editing exercise - Drs.
Martin Siegert, Frank Carsey, and Peter Barrett. Thanks are also given to Ms. Elizabeth Edwards
and Mrs. Linda Capper (BAS) for administrative assistance and media organization and to Lucy
Cavendish College for providing a most congenial setting for the meeting.
This final report was produced and edited by Ms. Debbie Paul of the Geochemical and
Environmental Research Group (www.gerg.tamu.edu) and Ms. Susan Wolff of the College of
Geosciences (geosciences.tamu.edu) of Texas A&M University.
The vast East Antarctic Ice Sheet is now known to cover numerous lakes that may
have existed for millions of years. The attention of the scientific community and the public
has been captured by these lakes with interest in the nature of resident biota, the age of the
lakes, the tectonic forces responsible for forming the lakes, and the record of Antarctic
climatic history that is likely to be contained in the sediments beneath them. Prominent
among these lakes is Lake Vostok, a remarkably large lake beneath about 4 km of ice in
central East Antarctica. In September 1999, a workshop was held in Cambridge, UK for
the purpose of developing a science plan for the exploration of subglacial lakes with
particular reference to Lake Vostok. In the course of these deliberations, it was concluded
that the biology of the lakes is intrinsically intertwined with a) the tectonic forces that have
given rise to the lakes, b) the glaciological and geophysical processes that control the
thermal and geochemical history of the lakes, and c) the climatic evolution of Antarctica.
Thus, the most fruitful scientific approach to the exploration of subglacial lakes is an
integrated investigation of the lakes and their environs as closely coupled systems.
The principal scientific goals to be addressed by subglacial lake exploration are:
1. to determine the form and distribution of life in the lake water, the sediment
below, and the ice above;
2. to recover climatic information contained in ice overlying the lakes and sediment
underlying the lakes; and
3. to understand the origins of subglacial lakes and its impact on the evolution of
life under the ice.
To accomplish these goals, integrated studies addressing a comprehensive set of
scientific objectives in glaciology, geology, microbiology, ecology, geochemistry, geophysics,
and limnology are recommended.
Significant technological developments will be required to enable the safe and timely
study of subglacial lakes. Development needs include: technologies to reliably access
subglacial lakes, in situ instrumentation to collect relevant information, devices for water
and sediment return to the surface, and methodologies for deploying devices and acquiring
samples from subglacial lakes without causing undue contamination or disturbance.
Stages of Exploration
Lake Vostok is the largest of the known subglacial lakes, and is a logical long-term
target for subglacial exploration through in-situ instrumentation and sample return.
However, there are clear benefits to a staged, progressive scientific program that includes:
- reconnaissance and mapping in analogue settings;
- the exploration of smaller lakes and possibly ice shelves;
- in-situ sensing of the water, sediments, and overlying ice of subglacial lakes;
- examination of water and sediment properties across subglacial lakes;
- water and shallow (<10 m) sediment retrieval; and finally,
- deep sediment (10-500 m) retrieval.
Guiding Principles for Subglacial Lake Exploration
The following requirements are recognized as essential for the successful
implementation of a subglacial lake exploration program:
1. The program must be internationally coordinated.
2. The program must be interdisciplinary in scope.
3. Non-contaminating technologies and minimum disturbance must be
fundamental considerations in program design and execution.
4. The ultimate goal must be lake entry and sample retrieval to ensure the greatest
scientific return on investment.
5. The best opportunity for attainment of important interdisciplinary scientific
objectives is the study of larger lakes, such as Lake Vostok, and therefore, Lake
Vostok, or its equivalent, must be the ultimate target of a subglacial exploration
To ensure continued progress toward the development and implementation of a
subglacial exploration program, the following actions are recommended.
1) In recognition of the international setting of the lake and the ambitious scope of
the scientific program it is recommended:
- that SCAR empanel a Group of Specialists on Subglacial Lakes to provide
interim guidance on science issues and
- that SCAR ask the Group of Specialists to consider and recommend
mechanisms for the international coordination of a subglacial lake
2) In recognition of the substantial resources and the wide range of skills required
to accomplish a subglacial exploration program, it is recommended:
- that SCAR encourage individual scientists to develop a consensus among
colleagues regarding the value of subglacial lake exploration;
- that SCAR ask National Antarctic Programs to gauge the interest of their
respective countries in implementing an international subglacial lake
exploration program; and
- that SCAR ask National Antarctic Programs to encourage and support
corollary studies that will provide the information necessary for developing
and implementing a subglacial lake exploration program.
3) In recognition of the technological and logistical challenges to be overcome, it is
- that SCAR ask the Council of Managers of National Antarctic Programs
(COMNAP) to convene a workshop to provide guidance on the technologies
needed for safe, contamination-free lake entry; sample retrieval; and logistics
- that SCAR ask COMNAP to facilitate development of an international
implementation plan emphasizing shared logistics and technology
SECTION I - THE SCIENCE PLAN
LIFE UNDER THE ICE AND THE EVOLUTION OF ANTARCTICA
The discovery of subglacial lakes has involved many scientists from several countries
(Russia, United Kingdom, United States, France and Denmark) over a period of more than four
decades. Observations of unusually flat areas atop the Antarctic ice sheet were compared to lakes
in other settings by a Russian pilot, R.V. Robison, in 1961 (Siegert 1999). Prior to this it had
been hypothesized from data obtained by the First Soviet Antarctic Expedition (SAE) in 1955-
57, that lakes could exist under ice sheets (Kapitsa 1998). In 1963 - 1964, a team led by A.
Kapitsa of the Moscow State University (the 9th SAE), studying the thickness of the ice sheet,
collected seismic traces adjacent to Vostok and serendipitously over Lake Vostok. These seismic
traces would ultimately lead to the recognition of liquid bodies of water under the ice sheet.
Confirmation of the existence of Lake Vostok came years later and took the collective efforts of
the 9th SAE ice cover studies; radio-echo sounding of the ice sheet by an international team led
by G. Robin during the 1973-75 airborne expeditions of the Scott Polar Research Institute
(SPRI), the US National Science Foundation, and the Technical University of Denmark; and the
results of ice sheet surface topographic studies using ERS-1 imagery at Mullard Space Science
Laboratory (Ridley 1993). Oswald and Robin were the first to use airborne radar to detect several
small subglacial lakes reporting their conclusions in 1973 (Oswald and Robin 1973). Once ERS-
1 information was available and a re-examination of the original Kapitsa seismic data had taken
place, the true scale of the lake was apparent, its importance became clear, and an international
workshop was convened in Cambridge in 1994. The discovery of Lake Vostok was first reported
at the 23rd session of SCAR in Rome in 1994 in a joint Russian- British report and the results
were published in the journal Nature (Kapitsa et al. 1996; Figure 1).
Figure 1. The location of Lake
Vostok on the East Antarctic
Ice Sheet (from Siegert 1999).
By 1996, speculation about the nature
of the lake was far reaching including the
suggestion that Lake Vostok water was most
likely contained fresh water and that the lake
would be expected to support a resident
microbial population. The interest in the
lakes continued to grow as an international
drilling team came within a few hundred
meters of the lakes liquid surface and
encountered what appeared to be ice accreted
from the lake water itself. The recognition of
a substantial layer of sediments underlying
the lake increased speculation on the forms
of life that might exist in the lake. It also has
become clear that many subglacial lakes
occur under the East Antarctic ice sheet and
that there may be a range of different types
Figure 2. The distribution of subglacial lakes (from
of lakes depending on their origins and
evolution over geologic time (Figure 2).
In the intervening years interest in the exploration of these unusual and remote bodies of
water led to additional workshops to develop a scientific rationale and plan for exploring
subglacial lakes (Lake Vostok: Scientific Objectives and Technological Requirements - an
International Workshop, St. Petersburg, Russia, 1998 and Lake Vostok: A Curiosity or a Focus
for Interdisciplinary Study? Washington, D.C., November, 1998). These workshops culminated
with an International Workshop on Subglacial Lake Exploration in Cambridge, England in
September, 1999 where the latest evidence about the nature of subglacial lakes was presented.
These deliberations and discussions have reached the point where a detailed scientific plan to
coordinate multi-disciplinary investigations of subglacial lakes is warranted. The following plan
provides a blueprint for making subglacial lake exploration a reality.
The scientific objectives for subglacial lake exploration focus on characterizing life in
extreme environments, deciphering the sedimentary and ice records with regard to the climatic
evolution of the Antarctic continent, and understanding how the origins of the lakes impacted the
evolution of life in the lakes. Subglacial lake exploration will be best accomplished by an
integrated, multi-disciplinary approach that includes the development of enabling technologies
(see Exploration Technologies). Subglacial lake entry and sample retrieval will address scientific
objectives within a range of disciplines including glaciology, geology, microbiology, ecology,
geochemistry, geophysics, and limnology. It is recommended that subglacial lake exploration
occur as a series of carefully designed stages with one stage dependent on the outcome of the
previous stage (see Stages of Exploration).
Subglacial lake exploration should include scientific investigations that will accomplish
the following goals.
GOALS OF SUBGLACIAL LAKE EXPLORATION
1) Determine the form and distribution of life in lake water, the sediment below, and the ice above.
2) Recover climatic information contained in ice overlying the lakes and in sediments underlying the lakes.
3) Understand the origins of subglacial lakes and its impact on the evolution of life under the ice.
Life Under the Ice
The study of subglacial lakes will provide an unprecedented view into an unique cold,
deep, subsurface environment. The compelling biological questions motivating scientific interest
in investigating subglacial lakes are related to three goals: 1) detection, characterization and
determination of any unique features of the indigenous organisms; 2) characterization of any
ecosystem’s function and structure; and 3) understanding the formation and history of the lake
basin as related to the evolution and natural history of lake biota. Subglacial lakes present an
extreme and unique environment in which to search for organisms that may represent novel
lineage’s or at least have evolved specialized adaptations. The search for life on other planetary
bodies in the solar system will be aided by the lessons learned from studies of extreme
environments on Earth, such as subglacial lakes (see Section II).
LIFE UNDER THE ICE - RATIONALE
The biology of subglacial lakes has developed and persisted in an extreme environment.
1) the lake environment is perennially high pressure, cold, dark, and isolated but the early lake may have been
2) the lakes are suspected of containing ultra-low levels of nutrients and if so, the low inputs of carbon and
essential elements over long-time periods will require organisms to evolve highly efficient metabolic strategies
to survive the most oligotrophic aquatic environments on earth;
3) novel organisms (and perhaps relict or fossil microbes) with unique adaptive strategies may be present in
4) any organisms present in the lake will have been isolated from related organisms for at least hundreds of
thousands of years and more likely for millions of years;
5) some lake environments and their biota may pre-date the glaciation of Antarctica;
6) hydrothermal vents may occur in some lakes and support high biological diversity;
7) atmosphere gases occurring as gas hydrate offer an unique environment for microorganisms;
8) knowledge of subglacial lake biology would further our understanding of how organisms evolve in relation to
climatic change; and
9) an understanding of subglacial biology will contribute to our understanding of the evolution of life on Earth and
the likelihood of extra-terrestrial analogues.
Scientific objectives related to the detection and characterization of life in subglacial
lakes present a number of technological challenges. While many techniques, such as DNA
fingerprinting and others, are now routinely used, the retrieval of uncontaminated samples from
such a remote and harsh environment will require innovative approaches and solutions. In
addition, it must be recognized that the lakes may be anoxic and the resident communities
predominantly anaerobic microbes. Sampling in a “clean” manner and retrieving samples under
in situ conditions will require technological developments and careful planning of experimental
LIFE UNDER THE ICE - SCIENTIFIC OBJECTIVES
1) determine the identity and diversity of life forms in the subglacial lakes and whether they are viable
2) determine the amount of biomass and density of each type of life;
3) elucidate any unique biochemical or physiological processes of subglacial lake organisms;
4) determine the progenitors of subglacial lake organisms and the conditions that support them;
5) determine which organisms are metabolically active;
6) determine in situ growth and metabolic rates of organisms;
7) determine the minimum amount of energy required for growth;
8) define the redox couples that support life (e.g., electron donors and acceptors);
9) ascertain the energy source(s) and how energy is extracted from the environment;
10) define the carbon sources that support life in the subglacial lakes;
11) determine the spatial location of organisms and organismal associations;
12) determine the evolutionary history of subglacial lakes and their biota in the sediment record; and
13) investigate the relationship between subglacial lake organisms and gas hydrate.
It is also suspected that subglacial lakes are one of the most oligotrophic environments on
earth, inferring that cell counts and biomass may be extremely low, challenging even the most
sensitive techniques. It is further recognized that the majority of microbes are not compatible
with standard culturing techniques and may go undetected unless broad spectrum assays and
guild approaches to metabolic functionality are employed. It has also been suggested that as a
result of the ultra-oligotrophic environment that most of the microbes are expected to be inactive
and/or starved again requiring unambiguous assays not only of the presence of biomolecules but
also an assessment of the metabolic state of any detected organisms.
While direct detection and characterization of the extant biota would provide the most
unambiguous descriptions of lake biota, indirect detection of the utilization of bioreactive
compounds may be the best first order indication that life sustaining processes are occurring. The
emplacement of chemical sensors would provide the best first measurement of relevant chemical
profiles and distributions within the lake to determine whether gradients in micro-nutrients and
metabolic products reflect the activity of biological organisms. In addition, confirmatory uptake
experiments both in vivo and in vitro may be necessary using the most relevant substrates and
retrieved water, ice and sediment samples to confirm the presence of life in subglacial lakes.
The Climatic and Tectonic Evolution of Antarctica
The geological history and evolution of subglacial lakes, and any biological communities
contained in them, are closely related to the tectonic evolution, the climatic history, and the
development of the ice cover of Antarctica. To understand subglacial lake systems a better
knowledge of lake physiography and morphology including information on lake sizes and
bathymetry, the thickness of the water column and ice cover, and the origin and distribution of
lake sediments is needed (Figure 3).
Ice-sheet dynamics will be critical to the
physical and chemical environment in subglacial
lakes. The ice sheet may supply melt water, gas
hydrate, and debris to the lake system. The ice
sheet may also regulate the exchange of water
between the lake and the ice base. Finally, the
gradients between ice and water are likely to affect
the circulation of the lake water. Ice penetrating
radar measurements upstream of the lakes can
detect areas of subglacial melting. Several
subglacial lakes are found in areas of enhanced ice-
sheet flow within major topographic troughs. It is
therefore possible that subglacial lakes may be
coincident with the development of ice streams.
Numerical models and airborne geophysical data
can be used to assess the role played by subglacial
lakes in enhancing ice flow.
Measurement of the physico-chemical
characteristics of the lake water column are needed
Figure 3. Description of the setting of Lake
Vostok (from Siegert 1999). to understand lake structure and dynamics. Data on
current velocity, current direction, salinity, temperature, pH, oxygen concentrations, and
suspended load will contribute to understanding the origins and history of the lake’s water.
Of particular interest is the geological genesis of subglacial lakes. Various scenarios have
been proposed. One possibility is that some lakes were formed before Antarctica first became ice
covered nearly 34 million years ago. If so, the sediments could include strata at depth which
were deposited before this time providing a unique archive of the pre-glacial climate of Central
Antarctica. Other lakes may have formed in-place under the glacier and thus, the sediments
provide information about the conditions that led to the formation of subglacial lakes and how
these lakes evolved over time in isolation from the atmosphere. The reconstruction of
environmental changes in the lake through time and their correlation with other paleo-records,
will contribute to an understanding of the relationships between the waxing and waning of ice
thickness, and changes in atmospheric temperature and precipitation patterns. The sedimentary
record may provide fossil evidence of the evolution of biological systems in the lakes as well.
The sedimentary record may also provide an indication of the flux of extraterrestrial
material (meteorites, micrometeorites, and cosmic dust) since the catchment of many of the lakes
is large and the lakes have been in place for long periods of time. The lake beds provide an
opportunity to document the flux of these materials over time frames of several millions of years.
It has been suggested that periodic changes in the accretion rate of extraterrestrial material is due
to a previously unrecognized 100,000 year periodicity in the Earth’s orbital inclination that may
be related to long term climate change.
CLIMATIC AND TECTONIC EVOLUTION OF ANTARCTICA - RATIONALE
• Geologically, subglacial lakes will provide insights into the evolution of the Antarctic
1) understanding of the East Antarctic geological terrain would be dramatically altered if
the terrain is an active tectonic rift;
2) the unique sedimentary record of the earth’s climate will provide information about the
initiation of Antarctic glaciation;
3) lake beds are a repository of extraterrestrial material being a catchment for the melting
of large volumes of ice; and
4) the sediment record would provide a climate record analogous to the overlying ice core
paleoclimate record and potentially provide a longer record of climate change before
• The geochemistry of subglacial lakes will be unique due to the extreme conditions:
1) lake environments are dark, cold, and high pressure;
2) unique geochemical cycles will have evolved in a system “closed” for at least hundreds
of thousands of years if not millions;
3) air gas hydrate should play a significant role in the biochemistry of lakes;
4) the carbon limiting environment of lakes and the extended time period without gaseous
exchange with the atmosphere should result in unusual stable isotope partitioning
amongst the various lake components;
5) utilization of alternative sources of biochemical energy sets the stage for an unusual
biogeochemical cycle; and
6) cold water carbonate systems may play an important role in the carbon cycle.
• The glaciology of the local and regional ice dynamics will provide insight into the
evolution and working of the Antarctic ice sheet and its role in global climate.
The scientific objectives related to the climatic and tectonic evolution of Antarctic are
ambitious and comprehensive. To attain these objectives collateral studies will be needed that
utilize existing information as well as collecting new information by studies other than those
directly related to lake entry and sample retrieval. However, the climate record recovered from
the ice overlying the lakes and the sediments underlying the lakes will be critical to climatic
evolution studies. To realize scientific objectives related to climatic evolution, a coordinated
series of activities will be needed. Ice cores and satellite images will need to be studied to
document the glacial regime over subglacial lakes both today and during the last glacial
maximum. To address questions related to the evolution of subglacial lakes it will be necessary
to map bedrock topography and gravity and magnetic fields beyond the lake margins. This is in
addition to mapping water depth and topography within the various lake basins. Sampling of the
ice column and surficial bedrock of the central Antarctic highlands will also be needed (i.e.,
Gamburtsev Mountains, Vostok Subglacial Highlands) to provide a regional view of the lakes’
tectonic setting. The in situ geochemical structure (salinity, temperature, major ions, gases,
nutrients, and currents) of the bodies of water in the lakes will provide important clues to those
processes occurring, and those that have occurred in the past, within the lake. The geochemical
information links directly to the biological investigations establishing a physical and chemical
setting for the temporal responses and spatial distribution of life forms in subglacial lakes.
CLIMATIC AND TECTONIC EVOLUTION OF ANTARCTICA - SCIENTIFIC
• Geology and Paleoenvironment
1) Decipher the sedimentological paleoclimate record (especially beyond that obtainable
from ice cores).
2) Establish the synchronicity of the paleoclimate record in the sediments and that of other
paleo-records (especially the Vostok ice core).
3) Determine the origins of sedimentary material in the basin over time;
4) Measure the geothermal heat flow to elucidate the origin and evolution of the lake.
5) Determine the flux of extraterrestrial materials over time and its relationship to the
recent 100,000 year periodicity in climate.
6) Understand the influence of the Antarctic Ice Sheet on subglacial lake sedimentation
through glacial-interglacial oscillations of the last 400,000 years.
7) Establish the tectonics of the region around subglacial lakes to understand the influence
of crustal processes on the early history of the ice sheet and on the origin and
maintenance of lake basins.
• Physiography of the Lake
1) Map lake topography, water-depth, and aerial extent.
2) Map lake sediment thickness and distribution.
3) Map bedrock topography, structure and lake bathymetry.
4) Provide evidence to determine the origin, evolution and age of the lakes.
• Glaciology and Ice Dynamics
1) Map ice sheet thickness and structure on and around the lakes.
2) Understand both the present “interglacial” and past “glacial” ice flow regime taking into
account the influence of subglacial topography and the effect of the lake itself on the
3) Understand the present day regime of subglacial lakes with the hydrologic balance
between glacial melting and refreezing and the “head-space” balance between lake floor
subsidence and sedimentation.
4) Decipher glacial fluctuations (including possible disappearance of the ice sheet) over the
last 15 million years and link it with proxy records of ice volume (e.g., 18O in deep sea
• Geochemistry and the Physical Environment
1) Establish the three-dimensional characteristics of the lakes environment (salinity,
temperature, major ions, nutrients).
2) Characterize the gaseous constituents (O2, CH4, N2, CO2, N2O) of the lakes water with
particular emphasis on determining the role of gas hydrate.
3) Determine the distribution of biologically reactive chemical constituents (nutrients,
sulfate, pH, methane) in the water column.
4) Determine the carbon budget, the processes that transform carbon within lake waters,
the couplings to the sediments, and interactions with any biotic systems.
5) Determine the physical redistribution of chemicals within lakes due to circulation,
advection and possible novel sources of chemicals.
Once access to a lake is provided on a regular basis, imaging of the seafloor will be
important to better understand its composition, variability, and suitability for direct lake
sampling. In addition to remote imaging, more ambitious in situ sediment sampling and
observations will need to be undertaken. One approach would be to emplace casing from the
overlying ice through the lake to provide for push coring and/or hydraulic coring deep (100 to
300 meters below the subsurface) into the sedimentary column leading to deeper penetration
(500+ meters below the surface) with low pressure diamond drilling to 500 meters. With this
system in place an Ocean Drilling Program (ODP) and/or Cape Roberts model could be followed
allowing for logging of physical properties (magnetic orientation and susceptibility, density,
porosity, etc.) to describe sediment texture and depositional structures. This access would also
provide discrete sediment samples for geochemical, physical and biological analyses. Once
available, the hole(s) would also be used to log subsurface temperature profiles (geothermal
gradients) and to gather seismic reflection data (VSP) to indicate lateral continuity in the
stratigraphy of the lakes’ sedimentary deposits. These comprehensive studies would provide the
information needed to decipher the climatic and tectonic history of Antarctica and how it
influenced the evolution of life under the ice.
The wide range of scientific objectives to be addressed suggest that innovative and novel
experimental approaches will be needed to acquire data and information on the subglacial
environment. Delineation of the scientific objectives aids in defining the enabling technologies
needed to explore subglacial lakes. The primary practical goal of subglacial lake exploration is to
access the lake water and sediments in a non-contaminating fashion to obtain physical, chemical,
and biological measurements and to provide water and sediment sample retrieval (Figure 4).
Many of the proposed activities will require the development and testing of new technologies,
methodologies, and protocols.
HOT WATER 1000m HEAVY
STERILIZATION BATH SENSOR
SONAR MAPPING TETHER
MINI VEHICLE 500m
DEPLOYED SIDE SCAN
Figure 4. One scenario for a subglacial lake observatory (F. Carsey, pers. comm.).
• Access Technologies
1) adapt current ice drilling and coring technologies to subglacial lake entry;
2) develop “clean” sample return protocols and methodologies;
3) develop in situ observatories that will survive the physical/chemical environment of subglacial
4) develop methodologies to emplace, service, and retrieve in situ observatories;
5) develop drilling techniques that minimize contamination and disturbance;
6) adapt and improve the technologies for shallow and deep penetration of sedimentary columns;
7) adapt logging tools for deployment in a subglacial environment.
• Non-Contaminating Systems and Procedures
1) develop entry and sample retrieval protocols that do not alter the nature of the lakes;
2) develop methodologies to return non-contaminated samples to the surface, especially from a
3) develop capabilities for return of samples at in situ conditions including possible anoxia; and
4) develop decontamination protocols for handling samples once retrieved.
• Robotics and In Situ Sensors
1) develop remote techniques to record and transmit data on relevant physical, chemical, and
2) adapt geophysical techniques for intra-lake imaging of the lake basin; and
3) develop technologies for exploring the lake from single entry points (i.e., tethered robotics).
• Sample Retrieval Techniques
1) develop methodologies for retrieving water, ice, and sediment in a non-contaminating manner;
2) develop techniques that allow for maintenance of in situ conditions during sample retrieval; and
3) develop methodologies to handle samples at one atmosphere that have been retrieved at in situ
pressure, temperature, and oxygen conditions.
• Miniaturization of Sensors and Sampling Devices
1) in situ sensors, observatories and sample retrieval systems must be accommodated through
2) sediment coring and sample retrieval must be accommodated through access holes of limited
3) down hole logging and other sensors to record sediment properties must be accommodated
through access holes.
Stages of Exploration
The wide range of scientific objectives will be best accomplished in a step-wise fashion.
Some experimental approaches are immediately possible (e.g., aerogeophysics), require limited
logistical support and provide important fundamental information for focusing follow-on
investigations. Other approaches will require substantial technology development and significant
logistical support. The technologies needed to implement the science plan are not presently in
place and will require a commitment of resources to develop these technologies as discussed in
the previous section (see Exploration Technologies).
WHERE TO EXPLORE?
A key consideration will be the choice of a subglacial lake (or lakes) for study that optimizes the scientific return for the
resources invested. Ideally, the choice of a subglacial lake (or lakes) should be based on:
1) Does the lake(s) provide the greatest likelihood for attaining the scientific goals?
2) Can the lake(s) be characterized in a meaningful way (i.e., size, postulated structure)?
3) Is the lake(s) representative of other lakes and settings?
4) Is the geological/glaciological setting understood?
5) Is the lake(s) accessible (closest infrastructure)?
6) Is the program feasible within cost and logistical constraints?
STAGES IN SUBGLACIAL LAKE EXPLORATION
Stage 1 - Reconnaissance and Mapping
- identify prospective locations for drill holes for ice/bedrock sampling, lake access, and lake sediment coring
- remote surveys of ice, water, and sediments associated with subglacial lakes
- perform geophysical surveys to establish the regional and local tectonic setting
- ground based and aerial surveys of subglacial lake sites
Stage 2 - Develop a Plan and Establish International Program Organization
- develop a Science Plan
- form a SCAR scientific advisory group
- form an international group with a science representative from each country with a significant stake in the
- form a group of national program managers representing each country with a significant stake in the program
- designate a program operator and host country
- agree on a budget for logistics
- finalize a draft Implementation Plan (Science, Logistics, and Timetables)
Stage 3 - Carry out Environmental Impact Assessment (EIA), Proceed with Ice/Bedrock Drilling of the Regional
Setting, and Test Lake Entry Techniques
- initiate an Initial Environmental Evaluation (IEE) for Regional Ice and Bedrock (RIB) drilling to establish the
glacial and tectonic setting
- finalize an IEE for RIB drilling
- carry out RIB drilling
- test lake entry and sediment coring technologies (with full environmental monitoring) on an ice shelf or at
- initiate a Comprehensive Environmental Evaluation (CEE) for lake entry and sediment coring
Stage 4 - First Sample Retrieval of Lake Water, Ice, and Shallow Sediments (10 m)
- finalize the CEE for lake entry and sediment coring
- drill access hole to lake
- in situ measurement of physical, chemical, and biological properties
- in situ sampling of lake waters (and perhaps glacial sediment) and ice for presence of life
- installation of observatories
- in situ imaging of the lake basin
Stage 5 - Sample Retrieval of Lake Water, Ice, and Deep Sediment (10-500 m)
- deploy casing through full lake depth to seal the sediment column from lake water
- push-core followed by hydraulic piston core followed by low pressure diamond drilling
- downhole logging (heat flow, etc.) inside cased hole if sediment is present
- seismic imaging by VSP inside the cased hole
- continued installation/retrieval of observatories
Stage 6 - Further Lake Sampling and Coring
- Repeat Stages 4 and 5 until lake access and sediment coring objectives are completed
Stage 7 - Remove Equipment and Clean-Up Camp Sites
Subglacial lake exploration has caught the imagination of the scientific community and
the general public. The challenge is to move forward in an orderly fashion to create the structures
and support needed to accomplish the scientific goals. The following guiding principles and
recommendations provide the foundations for the sound and scientifically rewarding study of the
unique environments represented by Antarctic subglacial lakes.
GUIDING PRINCIPLES FOR SUBGLACIAL LAKE EXPLORATION
The following programmatic requirements are recognized as essential for the implementation of subglacial lake
1) the program must be internationally coordinated;
2) the program must be interdisciplinary in scope;
3) non-contaminating technologies and minimum disturbance must be fundamental considerations in program design
4) to ensure the greatest scientific return, the ultimate goal should be lake entry and sample retrieval; and
5) the best opportunity to attain the interdisciplinary scientific goals is by study of larger lakes, such as Lake Vostok,
and therefore, Lake Vostok, or its equivalent, must be the ultimate target for study.
To fully understand the origins, history and present content (both living and non-living)
of these lakes; a coordinated and integrated science program must be pursued. Given the
logistical challenges, the resources needed and the location of the proposed studies, international
cooperation and partnering will be essential to developing a feasible and realistic field campaign
to explore subglacial lakes. In addition, and in recognition of the unique position of Antarctica
and the novelty of subglacial lakes, caution must be exercised in all facets of the program to
ensure stewardship of natural resources. Any investigatory program should strive to eliminate or
minimize not only disturbance of the lakes but also the surrounding environment. Based on these
precepts the following recommendations are considered essential to the development,
implementation and conduct of a subglacial lake exploration program.
RECOMMENDATIONS FOR ADVANCING SUBGLACIAL LAKE EXPLORATION
1) In recognition of the international setting of the lake and the ambitious scope of the scientific program it is
- that SCAR empanel a Group of Specialists on Subglacial Lakes to provide interim guidance on science
- that SCAR ask the Group of Specialists to consider and recommend mechanisms for the international
coordination of a subglacial lake exploration program.
2) In recognition of the substantial resources and the wide range of skills required to accomplish a subglacial
exploration program, it is recommended:
- that SCAR encourage individual scientists to develop a consensus among colleagues regarding the value
of subglacial lake exploration;
- that SCAR ask National Antarctic Programs to gauge the interest of their respective countries in
implementing an international subglacial lake exploration program; and
- that SCAR ask National Antarctic Programs to encourage and support corollary studies that will provide
the information necessary for developing and implementing a subglacial lake exploration program.
3) In recognition of the technological and logistical challenges to be overcome, it is recommended:
- that SCAR ask the Council of Managers of National Antarctic Programs (COMNAP) to convene a
workshop to provide guidance on the technologies needed for safe, contamination-free lake entry; sample
retrieval; and logistics and
- that SCAR ask COMNAP to facilitate development of an international implementation plan emphasizing
shared logistics and technology development.
SECTION II - STATE OF THE KNOWLEDGE OF SUBGLACIAL LAKES
Recent analysis of airborne geophysical records has indicated the presence of more than
60 subglacial lakes under the East Antarctic icesheet (Siegert et al. 1996; Dowdeswell and
Siegert 1999; see Figure 4). An aerial survey of approximately half of the East Antarctic ice
sheet with 60 MHz radio-echo soundings indicated the presence of many subglacial lakes. At
low temperatures, ice is relatively transparent to radio waves at 60 MHz frequency and radio-
echo sounding has successfully penetrated to the base of ice more than 4 km thick. Subglacial
lakes are identified by strong reflections from the ice sheet base, echoes of constant strength
along the track, and the very flat and virtually horizontal character of the reflective surface.
These characteristics are indicative of water at the base of the ice sheet but water saturated
sediments may produce a similar signal. The majority of subglacial lakes (70%) are found close
to ice divides where the slope of the ice surface and ice velocity are small. The thickness of the
ice overlying the lakes varies from 2333 to 4200 m (Figure 5). The length of the lakes varies
from 1.3 to 280 km. About 75% of the lakes have radio echo lengths of less than 10 km and only
5% of the lakes have lengths greater than 30 km. Other than their location, very little is known
about these lakes. Interest in recent years has focused on one lake in particular, the largest lake
detected so far - Lake Vostok.
Despite the relatively sparse information on subglacial lakes beneath thick ice cover,
other analogues provide clues to what the characteristics of these water accumulations might be.
The subglacial environment is expected to be one of the most oligotrophic environments on
Earth, an environment with low nutrient levels and low standing stocks of viable organisms if
present at all. Alpine subglacial environments and permafrost are known to accommodate
thriving bacterial communities (Sharp et al. 1999; Gilichinsky et al. 1995). However, these
environments are not as extreme (e.g., pressure and temperature) as subglacial environments
beneath large ice sheets. Alpine subglacial environments are also subject to influxes of nutrients
and other essential life sustaining elements on a regular basis that may not be occurring in
Within the geological record, analogues of modern subglacial lakes may be present in the
Neoproterozoic record of 750 to 542 million years ago. It has been suggested that during this
period the earth experienced a number of massive glaciations - covering much of the planet for
approximately 10 million years at a time. The evidence for an ancient ice covered planet comes
from thick widespread sedimentary sequences deposited at the base of large ice bodies. These
glacial units alternate with thick carbonate units derived from warm, shallow water sedimentary
deposits (Hoffman et al. 1998). These paired sequences have been interpreted as representing a
long period when the earth alternated between an extremely cold, completely ice covered planet
and a “hothouse planet”. Portions of the Antarctic subglacial environment today, which have
been isolated from free exchange with the atmosphere for at least 10 million years, may be
similar to the environment of these ancient times.
Additional important information regarding the contents of subglacial lakes comes from
ice core studies. Viable organisms have been detected to at least depths of 2,400 m in the East
Antarctic ice sheet at Lake Vostok (Abyzov 1993). Sampling of ice in the interior of Antarctica
Figure 5. The locations of lakes beneath the Antarctic ice sheet (marked by triangles), identified from 60 MHz airborne radio-echo
sounding records (from Dowdeswell and Siegert 1999).
has demonstrated the presence of microorganisms characteristic of atmospheric microflora at
even remote locations (Lacy et al. 1970; Cameron et al. 1972). Viable organisms have been
recovered from million-year-old Antarctic permafrost suggesting that prolonged preservation of
viable microorganisms is possible even in the extreme cold (Cameron and Morelli 1974). These
analogies suggest that viable microorganisms will be found in subglacial lakes. Even more
compelling evidence is presented for the presence of life in Lake Vostok in the following
Subglacial Lake Conceptual Model
Subglacial lakes are essentially the product of an interaction between geological and
glaciological features (Figure 6). Geothermal heat, trapped beneath a thick ice sheet, raises the
temperature of the basal ice and when this exceeds the pressure melting point, water is formed.
The development of a sub-glacial lake however requires the existence of an appropriate rock
basin to contain the melt water. This can either be a basin formed pre-glaciation or glacially
scoured. The persistence of the lake will be primarily dependent on changes in ice thickness,
linked to climate changes. If a lake existed in a rock basin pre-glaciation, its persistence under
the developing ice sheet would require the lake to have been of substantial depth to avoid
freezing solid and losing sediments through glacial scouring. Only the very largest lakes are
likely to fulfill this requirement.
Figure 6. A conceptual model of a subglacial lake (C. Ellis-Evans, pers. comm.)
The nature of the lake environment will be dependent on a wide range of variables.
Geological influences will include the geochemical composition of the bedrock, tectonic activity
in the underlying geology, local scale geomorphological features and the possible presence of
pre-glaciation limnetic sediments in addition to subglacial sediments derived from glacial scour.
Glaciological influences will include the thickness of the ice sheet, possible changes in ice
thickness across the lake area, ice velocities and direction of ice flow over the lake and the
chemical status of the ice. Glaciological influences are essentially direct manifestations of
climate changes over time. The nature of a lake is also a function of age as lakes are essentially
an integration of the surrounding catchment and climate. There is a move towards
thermodynamic equilibrium in all natural systems, which will reflect the interplay of various
environmental variables. The presence of biological activity in limnetic systems can disrupt the
state of chemical equilibrium and would likely be detected by discontinuities in
Figure 7. Process model of a subglacial lake (C. Ellis-Evans, pers. comm.).
The sub-glacial lake environment will have physical and chemical components that are
responsive to environmental variables and it is possible that such environments also have a
similarly responsive biological component. The potential glaciological influences will be
manifested through a half-million year time delay on atmospheric exchange with the lake, as a
potential heat sink and thermal insulator, through the establishment of horizontally varying
temperatures in the upper layers of lake water (due to varying ice thickness and freeze/melt
processes) which could facilitate an internal circulation, downward pressure of ice establishing a
high pressure lake environment and the contribution of gases, dissolved chemical species and
particles, including potentially viable propagules via melting of basal ice.
The geological influences will clearly include geothermal heat input and contributions of
glacially scoured bedrock. These heat inputs will be critical to the formation and maintenance of
sub-glacial environments. The bedrock inputs slow heat transfer, relative to water, the fine-
grained scour material represents a large geochemically reactive surface area and creates a
favorable location for biogeochemical gradients by restricting diffusion rates. The large surface
area of scoured material also provides attractive sites for biological colonization. The distribution
of bedrock scour within a sub-glacial system alters the morphometry of the lake over time and
potentially influences the distribution of physical, geochemical and biological processes. These
sediments may be augmented by sedimentation from the overlying ice sheet and by the presence
of pre-glaciation sediments. The inputs from the ice sheet are likely to be miniscule in volume
compared to glacial scour inputs but may include critical elements such as gases and viable
propagules. The presence of ancient sediments pre-dating glaciation would likely provide inputs
of organics and a potentially diverse biota whereas organics and biota are likely to be extremely
limited from glacial scour inputs. Such sediments tend to accumulate towards the deeper parts of
the lake whereas the glacial scour inputs would predominate in the region where ice cover first
moves over the lake margins. The presence of ancient sediments would further enhance the
heterogeneity of sediment distribution and characteristics.
Further geological inputs to sub-glacial lakes could include geothermal hot spots and,
possibly, hydrothermal vents which would yet again increase the heterogeneity of the sediment
environment, resulting in localized geochemical and biological discontinuities and imposing
some degree of impact on the whole lake. The presence or absence of circulation within a lake
would be an important consideration for scaling the influence of geothermal hotspots within
subglacial lake environments.
A consequence of high pressures and low ambient temperatures can be the production of
gas hydrate. Gas hydrates bind dissolved gases in a crystalline matrix, so reducing the potential
for dissolved gas interaction with other lake components (chemistry and biology). Different
hydrated gases may be distributed on the basis of density throughout the lake. Chemical
equilibrium is an inevitable consequence for environments sealed from the oxidizing atmosphere
for long periods of time. The presence of substantial amounts of reduced substances (perhaps
from hydrothermal vents) and/or the presence of biological respiration will accelerate the
process. Countering this drive towards reduced conditions would be the potential release of
oxidants from the ice sheet and from glacially scoured bedrock, but the presence of gas hydrate
rather than dissolved gases could feasibly restrict this counter-influence. Even if gases were
available the input may prove inadequate to counter the shift towards more reduced conditions.
The drive towards chemical equilibrium will be a function of time and so the age of a sub-glacial
lake will influence its thermodynamic status. The presence of circulation would further
contribute to the drive towards equilibrium.
If the ice sheet thickness varies across a sub-glacial lake, there will be potential for both
melting and freezing in the basal ice sheet and underlying water. This process will drive
circulation within a lake. Melting will contribute gases, dissolved chemical species and
particulates and represent a net gain for the sub-glacial lake. Accretion of lake water to the base
of an ice sheet conventionally results in exclusion of dissolved gases and many chemical species
from the water as it freezes resulting in a concentration effect for ions within the water column of
the lake. If all gases are in a crystalline hydrate form freezing could incorporate these crystal
structures into the basal ice sheet and gases would be thereby removed from the lake water.
Life Under the Ice
Existing Data - As water and sediment samples have not as yet been obtained from
subglacial lakes, the only available source of material with a sub-glacial origin is that present in
the accreted ice layer into which the Vostok ice coring program has penetrated. Two independent
groups (Karl et al. 199l; Priscu et al. 1999) have analyzed samples of accreted ice from depths of
3590 m and 3603 m in the Vostok ice core and both have reported the presence of active
bacteria. Cell counts ranged from 2-3 x 102 ml-1 in the 3603 m sample to 2.8-36 x 103 ml-1 at
3590 m. Assuming partitioning of bacterial cells between the ice cover and the lake water during
accretion was similar to that observed in Antarctic Dry Valley lakes, the accreted ice counts
would suggest cell numbers in the range 104-106 ml-1 for the Lake Vostok water column. The
gram-negative biomarker lipopolysaccharide was detected at concentrations consistent with the
cell count data suggesting a population dominated by Gram-negative bacteria (Karl et al. 1999).
Molecular analysis of the 3590 m samples using 16S rDNA with PCR, terminal restriction
fragment length polymorphism (T-RFLP) and sequence analysis revealed no evidence of
Figure 8. Microscopic analysis of melt samples from acreted Vostok ice (A-D) and the cross
polarized image of an ice core section (Priscu et al. 1999; Karl et al. 1999).
Archaea but five unique sequences could be attributed to extant members of the beta-
Protebacteria, Acidovorax (4) and Comamonas (1). One sequence was comparable to the Afipia
subgroup of the alpha-Proteobacteria and another to the Actinomyces (Priscu et al. 1999).
Earlier studies of the top 2000 m of the Vostok ice core revealed culturable micro-
organisms and a high correlation between cell concentrations and dust particle density (Abyzov
et al 1998). The fact that the above sequences are very closely related to sequences of modern
bacteria that are broadly distributed could indicate that these bacteria were dust-blown
propagules and entered the lake from the overlying ice-sheet. The low diversity seen in the
Vostok ice samples may be significant with respect to the predicted ultra-oligotrophic status of
the lake water. However extrapolating results from proxy samples such as accreted ice to the
sub-glacial context must be viewed with caution. Another interpretation of these data is that the
microbes are not from the lake but from contamination of the ice core samples during the drilling
process or in subsequent sample handling before dispatch of the samples to the American
laboratories. The accreted ice studies may represent the first indications that bacteria are present
in the water column of a sub-glacial lake but the findings need further investigation, as the issue
of possible contamination has yet to be resolved.
Diversity - The availability of modern molecular and microscopical tools offers the
facility to establish the presence of life within sub-glacial environments, to describe the
microbial diversity in considerable detail and to establish the degree of divergence from modern
relatives. This provides a significant opportunity to further understanding of microbial evolution
by comparing organisms from an environment long isolated from the atmosphere with those
from extreme environments not experiencing long-term isolation. The facility of modern
molecular techniques to identify organisms without culturing is particularly relevant in ultra-
oligotrophic environments where small biomass and resistance to culturing are common features
and could prove a significant issue for researchers here.
Figure 9. Scanning electron microscope and atomic force micrographs of particles within the
ice core (Priscu et al. 1999).
If subglacial lakes are of the order of 1-2 million years old, it can be anticipated that
physiological adaptations will have taken place within representatives of the biota alongside
selection processes driven by environmental variables. A “founding population” or inoculum
could come from either the eroded bedrock, from aerial microbiota trapped in the ice and
subsequently deposited in the lake or from lake sediments present prior to ice cover (a scenario
that would probably be restricted to the largest lakes). Assuming the smaller lakes formed
significantly after Antarctic glaciation was well established, microbiota would not have been
isolated long enough to express evolutionary or mutational mechanisms of genetic change,
especially recombination and mutator genes, and so alter the phenotype allowing for adaptation
to the lake's conditions. Larger lakes such as Lake Vostok may also have a relatively recent
origin (1-2 million years) but there are grounds for believing that such lakes may pre-date
glaciation and on such extended timescales changes in genotype and even phenotype might then
reasonably be expected.
In considering the possible biotic composition of sub-glacial lakes, other Antarctic lakes
provide useful insights. In oligotrophic lake systems the vast majority of observed diversity
resides in or on the sediments and relatively low diversity is found in the water column. This
suggests a broader base of biodiversity in sub-glacial lake sediments than in the overlying water
column and this would potentially be further amplified in those lakes inheriting sediment
deposits from a pre-glacial period. Antarctic lakes are markedly lower in overall species diversity
than equivalent Arctic or temperate climate lake environments (Vincent 1997). This can be
attributed, in large part, to the geographical isolation of Antarctica from other continents and the
youthfulness of the lakes. However, biogeographical studies suggest that whilst isolation does
affect the diversity of higher organisms this in not necessarily true for microorganisms such as
protozoa (Butler 1999). Bacterial diversity in Antarctic lakes is substantial (Ellis-Evans 1996)
and can in fact be comparable to temperate systems (E. Stackenbrandt, pers. comm.). Whilst
geographical isolation and a harsh environment clearly need not restrict diversity the time scale
of physical isolation and possible energy source limitations are likely to impact significantly on
subglacial lake bacterial diversity. Fungi are found in both maritime and continental Antarctic
lakes (Ellis-Evans 1985); but do not show significant diversity and their occurrence in Lake
Vostok is less certain. Recent studies have demonstrated the presence of aquatic viruses in a
range of Antarctic lakes, suggesting a ubiquitous presence (Kepner et al. 1998; Wilson et al. in
press). This would suggest that if bacteria are present in sub-glacial lakes then viruses will also
be present. More complex organisms, including protozoa, and micro-metazoans, such as rotifers
and tardigrades, are widespread in Antarctic surface lakes but metazoan diversity is very low.
The presence of such organisms (especially metazoans) in sub-glacial lakes is considered to be
unlikely in the absence of a proven substantial energy source to support the greater energy needs
Ecology - Microorganisms have developed biochemical, physiological, and
morphological diversity to facilitate their presence in most, if not all, environments on Earth.
This diversity encompasses organisms with novel redox couples for the production of energy;
adaptations to extremes of temperature, salt, and pH; novel energy acquisition mechanisms; and
unique strategies for withstanding starvation (Madigan and Marrs 1997). Studies of
microorganisms in Antarctic and Arctic permafrost soils have cultured strains of microorganisms
that are more than one million years old and analyses of Vostok ice cores have demonstrated
viable micro-organisms in the ice sheet above the lake (Abyzov 1993). Some of the ancient
Arctic strains grow relatively rapidly at -4.5ºC (Gilichinsky et al. 1995). Hence, growth at sub-
glacial temperatures (-3 to -4ºC) would not appear to be necessarily limited by temperature. The
vast majority of microbes isolated from Antarctic soils, freshwaters and air samples have proven
to be psychrotolerant rather than psychrophilic as physiological flexibility is a useful attribute in
most polar environments. The highest proportional representation of psychrophiles is seen in the
Antarctic marine environment where consistently cold temperatures have existed over
evolutionary time scales. This may be a clue to the likely physiological characteristics of any
Given the ultra-oligotrophic nature of the environment organic carbon, nitrogen and
phosphorus are likely to be in short supply and, as is the case in most aquatic environments, the
bulk of these microbes would be inactive and/or starved particularly within the water column.
Most aquatic microbes are thought to naturally live in a state of long-term starvation broken by
occasional “feasts”. There is little information on how long organisms can remain starved as
laboratory experiments do not translate easily to the environment. Reduction in cell size, loss of
certain redundant cell processes and increased damage resistance are features of starved cells
(Kjellberg et al. 1987) which can recover normal features in a more favorable environment. In
ultra-microbacteria these starvation characteristics are permanent features and this taxonomically
ill-defined group is frequently encountered in oligotrophic lakes so could feasibly form part of a
Certain fundamental maintenance processes have to occur within a vegetative microbial
cell for life to continue and this is an inescapable drain on cell resources. Spore formation is a
successful long-term survival mechanism for certain bacteria as spores are highly resistant to
environmental pressures. However the vegetative cells that emerge from spores still have
physiological limits and spore-formers are uncommon in Antarctica (Ellis-Evans 1996). It has to
be considered that any investigation of life in sub-glacial lakes will have to consider fossil
evidence of life and here the detection of specific biomolecules may be an important stratagem.
In contrast to the lakes in the ice-free regions of Antarctica, which all receive light energy
inputs at some point each year, sub-glacial lakes are permanently dark and the only energy
sources available would be based on organic and inorganic compounds. Substrate availability
will be a major issue particularly for heterotrophic microorganisms in ultra-oligotrophic sub-
glacial lakes. Microbial isolates from maritime Antarctic lakes have been shown capable of
utilizing exceptionally low levels of carbon and nitrogen at temperatures around 2ºC (Herbert
1981) but these substrates are the readily assimilable forms that can be utilized by most
organisms. With rock and ice dominated catchments, the most ready source of substrates in polar
lakes is invariably the limnetic sediments. Sub-glacial sediment material generated by glacial
scour and sedimentation of materials trapped in the ice sheet often contain very little organic
matter. Pre-glacial sediments(if they occurred) might well have contained considerable amounts
of organic material before the lake became sealed beneath the ice sheet. However, readily
assimilable material would likely have eventually been metabolized to carbon dioxide over the
long period of isolation leaving only the more recalcitrant organic material. In cold
environments, including Antarctic lakes, macromolecule breakdown represents a major limiting
step in nutrient recycling particularly as the proportion of aquatic DOC capable of breakdown
decreases with lower temperatures (Michaelson et al 1998). In ultra-low nutrient environments,
nutrient cycling is very tightly coupled as lysis of microbial cells often provides most of the
nutrients utilized. It has to be recognized that the current understanding of aquatic microbial food
web interactions may not be entirely appropriate to a sub-glacial lake context.
In the absence of photosynthesis and photorespiration, micro-organisms can derive
energy from geothermally driven chemical disequilibria (chemosynthesis). The chemical
products of such activity represent a range of oxidation-reduction potentials and organisms can
harvest energy by coupling energetically favorable oxidation and reduction half-reactions [see
Figure 10). By such mechanisms, micro-organisms have extended the envelope of habitable
conditions to encompass most of the extreme environments as yet studied on Earth. With the
exception of certain thermophilic organisms, virtually all the major chemosynthetic groups as yet
discovered also occur in polar environments (Ellis-Evans 1996).
Redox Potential (W)
CH2O ¨ CO2
CO2 ¨ CH20
H2 ¨ H H ¨ H2
NH4 ¨ N2 N2 ¨ NH4
CH4 ¨ CO2 CO2 ¨ CH4
H2S ¨ S S ¨ H2S
H2S ¨ SO4 SO4 ¨ H2S
Fe ¨ Fe (0H)3 Fe (OH)3 ¨ Fe
+ 2- NO3 ¨ NH4
NH4 ¨ NO3 2-
NO3 ¨ NO2
Mn ¨MnO2 MnO2 ¨ Mn
CO ¨ CO2 CO2 ¨ CO
NO3 ¨ N2 N2 ¨NO3
Figure 10. A range of oxidation potential (redox) and associated intermediate oxidation-
reduction reaction pairs. Geothermally driven chemical disequilibria can
provide a source of energy for microbiota in most environments. Microbes
exploit these thermodynamically favoured reactions and diverse combinations
of oxidants and reductants support various metabolic life styles (after E.J.
Gaidos et al. 1999. Science 284:1631, 1999).
Redox pairs are clearly depleted by both biological activity and abiotic reactions and
within a sealed system without access to an external supply of energy, natural chemical
equilibration would in time ultimately result in the end of life in this environment (Elderfield
and Schultz 1996). For life to exist long term in sub-glacial lakes it is necessary to invoke a flux
of oxidants to these environments. These can clearly be generated from the ice sheet and from
glacial scour products but does the input match the demand? Sub-glacial lakes formed after the
ice sheet had reached its current thickness would have small microbial populations derived
primarily from the ice sheet, relatively small amounts of reducing sediments and possibly not
have been in existence long enough to deplete the available store of oxidants. However, if a sub
glacial lakes existence extended back before glaciation, the time scales for depletion and
chemical equilibration would be much longer, reducing sediments would likely be more
prevalent and so depletion of oxidants could feasibly have reached critical levels for biological
activity if supply was insufficient.
The possibility of hydrothermal activity in certain sub-glacial environments has been
proposed and could in certain circumstances locally enhance biodiversity significantly but whilst
hydrothermal activity does offer reductants, which can be used in certain microbial processes, it
does not offer a source of oxidants. The abyssal vent ecosystems are dependent on a supply of
oxidants (such as sulfate, oxygen and nitrate) from the overlying ocean reaching vent microbes.
If these are not forthcoming, micro-organisms are ultimately restricted to low energy processes
such as methanogenesis and elemental S reduction. The issue of redox status therefore has
potentially major implications for biodiversity in these lakes.
Given the significance of oxidants, establishing the nature and role of gas hydrate in sub-
glacial lakes may be critical to understanding the sub-glacial ecosystem. Air hydrate is almost
certainly entering Lake Vostok, and possibly other sub-glacial lakes. At in situ temperatures and
pressures these hydrates would likely remain intact potentially making gas utilization by the
biota difficult. A further impact on carbon cycling in sub-glacial lakes could also result if
temperature and pressure conditions allow formation of carbon dioxide hydrates in the
sediments. However the microbiology of gas hydrates is only a recently developing area, focused
largely on methane hydrates in the deep ocean, and as yet still poorly understood.
The extreme environment of sub-glacial lakes is apparently characterized by high
pressures, low temperatures, permanent darkness, limited nutrient availability, the presence of
gas hydrates, potentially limited oxidant availability and temporally stable conditions. Such
unique environments offer the potential to find unique microbial assemblages and physiological
adaptations. Studying these ecosystems will however require an awareness of the pristine nature
of the environment and the absolute need to strictly control contamination issues if the
environmental values of sub-glacial lakes are to be preserved and the community structure (if
present) correctly described.
Climatic and Tectonic Evolution of Antarctica
The subglacial lake environment is at present very poorly known because no direct
measurements have been made of physical or chemical properties, or of the possible processes
such as basal melting and water circulation that could provide energy and nutrients for life in its
waters. Therefore to provide a context for this life, the extent of the water body along with
thickness of ice cover and water needs to be known, but also the dynamics and the state of
balance in physical and chemical lake processes must be understood. This in turn requires a
detailed knowledge of present day ice flow and ice sheet stability on a time scale of 105 or 106
Ice-sheet dynamics will be critical to the assessment of the environment of subglacial
lakes. The ice sheet may supply melt water, gas hydrate, and debris to the lake system. The ice
sheet may also regulate the exchange of water between the lake and the ice base. Finally, the
gradient of the ice-water is likely to affect the circulation of the lake water. Isochronous internal
layering across subglacial lakes is often continuous and traceable over 10s of km. The internal
structure of ice sheets and the 3-D particle flow paths can be constructed by mapping internal
layers. The resulting flow-path information can be used as a boundary condition for numerical
ice-flow model results, to gain quantitative information about the ice-sheet dynamics over and
around subglacial lakes (Siegert et al. 2000).
An additional reason for understanding the dynamics and state of balance in lake
processes is to help interpret the depositional record of Lake Vostok millions of years into the
past. This record is preserved in the 500+m of sediment beneath the floor of the lake as a
consequence of the release of extraterrestrial and terrestrial dust from the basal ice and its burial
of organics from both ice and lake. While it is unwise to claim too much for a depositional
record of a type never before seen by geologists, it is a record that must have been influenced by
variations in the overlying ice flow. It could well have recorded the passing glacial and
interglacial episodes not only through the last 4 interglacials found in the deep ice cores, but
extending back in time for millions of years.
The extent of this record beneath the Antarctic ice sheet is critically dependent on the
climatic evolution of Antarctica, which in turn has been both a consequence of, and influence on,
the decline in planetary temperature over the last 50 million years (Figure 11). These changes
have been linked to the breakup of the Gondwana supercontinent. According to current thinking
ice sheets begin Subglacial lake
20 sheet develops alternating
T I M E
Millions of years
40 ice sheets?
0 5 10 15
Change in Temperature (°C)
after Barrett, 1999
Figure 11. Planetary temperature over the last 100 million years (after Crowley and Kim
1995) showing significant points in the history of the Antarctic ice sheet and a
possible history for sedimentation in Lake Vostok.
the first Antarctic ice sheets formed around 34 million years ago, as a result of thermal isolation
through the southern continents separating from Antarctica, and the present permanent ice sheet
formed around 15 million years, when that separation was essentially complete. The sediment
beneath the larger subglacial lakes of today has recorded the forms of life in the lake and features
of the environment for much or perhaps even all of the period of permanent ice cover. It is also
possible that the oldest lake sediment records life and climate even before the first ice sheets
formed. The length of this record depends on tectonic setting and history, which is as yet
unknown even for the largest Lake Vostok.
Various scenarios for the history of subglacial lakes have been proposed, though mostly
relating to Lake Vostok. The subglacial topography of central Antarctica with the elongate shape
of Lake Vostok lying on the boundary between the Vostok Subglacial Highlands and the Aurora
Subglacial Basin (Figure 12). Consideration of this along with the depth of sediment beneath the
lake from Russian seismic data, suggests that the depression now occupied by Lake Vostok is a
rift basin of long standing (tens of millions of years or more). If the lake first formed
Figure 12. Bedrock map of Antarctica (from Drewry 1983) showing the location of Lake Vostok
at the boundary between the Vostok Subglacial Highlands and the Aurora Subglacial
in this depression prior to 34 million years ago then we would expect the oldest sediments to
predate the first of the Antarctic ice sheets, and thus be a unique archive of the last vegetation
and climate of preglacial central Antarctica. Much of the Lake Vostok record will represent
conditions of permanent ice cover that has varied little over the last 15 million years. These
sediments will provide information about the conditions that encouraged the formation of
subglacial lakes and how these lakes evolved over time in isolation from the atmosphere. The
reconstruction of the environmental changes in lakes through time and their correlation with
other paleo-records, will contribute to an understanding of the relationships between the waxing
and waning of ice thickness, changes in atmospheric temperature, and precipitation patterns. The
sedimentary record will also provide fossil evidence of the evolution of any biological systems in
The sedimentary record in the northern end of Lake Vostok will also provide an
indication of the flux of extraterrestrial material (meteorites, micrometeorites, and cosmic dust
from melting ice transported in suspension from circulating lake waters). This would provide an
unparalleled opportunity to document the flux of these materials over time frames of several
millions of years. It has been suggested that periodic changes in the accretion rate of
extraterrestrial material is due to a previously unrecognized 100 Kyr periodicity in the Earth’s
orbital inclination that may be related to long term climate change.
An Extraterrestrial Analogue
The ice-covered Galilean moons, Europa and Callisto, are thought to harbor large, old,
subsurface oceans (Figure 13). Recent modeling of the cycloidal fissure features on the surface
of the Europan ice sheet suggest the ice cover thickness to be comparable to that overlying Lake
Vostok but far more dynamic. Lake Vostok is a glacial environment whereas the European ice
sheet is effectively sea-ice. Consideration of the biogeochemical nature of the ocean environment
of Europa suggests that the presence of metazoans would be highly unlikely and that even
microbial physiological diversity would be limited by the absence of sufficient oxidized energy
sources in what is likely to be a highly reducing environment. If life ever developed on Europa it
was very likely in prehistory and tracing the fossil records, particularly if limited to robotic
approaches, will require an understanding of how life survives under constant low temperatures,
limiting nutrients and minimal energy resources. At both Earth and planetary sites, the issue of
evaluating habitat and bioenergy sources will be crucial. Ultra-oligotrophy further suggests that
life could be limited to highly specialized microbial communities with small populations.
Microbiologists are revolutionizing our understanding of the biodiversity of life on Earth and
repeatedly finding microbes thriving in sites long considered untenable for life. This approach
will clearly have value in exploring subglacial lakes and may have relevance in any search for
life on Europa. Applying such approaches to subglacial lakes may not necessarily directly
Icy Cliffs on Europa
Figure 13. The ice-covered moon of Jupiter, Europa (courtesy of NASA/JPL).
advance our knowledge of life on other planetary bodies but would significantly enhance our
appreciation of how these and other life detection techniques can be equated with technological
issues such as the need for miniaturization, robustness, and preventing or minimizing
contamination of pristine environments.
The exploration of subglacial lakes and Europa/Callisto have much in common. The chief
similarity is in the primary scientific goals for subglacial lake exploration and the Jovian satellite
oceans, the search for life. In the Jovian system, this search must be carried out robotically, and
the robotic approach has much to offer in various sites on Earth where issues such as
contamination prevention and remoteness make sample recovery challenging. Subglacial lakes,
in particular, are a site in which low temperatures, high pressures, low salinity, isolation, and
great age indicate an oligotrophic environment. This suggests that life could occur in highly
specialized microbial communities with small populations. This situation may not be
representative of Europa or Callisto, as these sites may be prehistoric. However, the exercise of
locating and examining life which is present in small numbers is clearly excellent preparation for
sites which may have no life forms at all. At both Earth and planetary sites, the issue of
evaluating habitat and bioenergy sources will be crucial.
In addition to the physical and scientific similarities, the technologies required for
accessing and studying the liquid water domains at in subglacial lakes and Europa/Callisto have
numerous elements in common, many of them quite challenging. Both sites require vehicles that
can move through great distances of ice, 4 to 10 km vertically; both sites require communication
of data through the ice and water; both sites require sophisticated instrumentation to locate and
describe life and evaluate habitats; and both sites call for exploration with little basic data on site
characterization as they are unknown places. In addition, it is worth noting that NASA missions
to planetary sites can only take the smallest quantity of equipment and yet are required to do a
sophisticated job. These kinds of capabilities could greatly benefit Earth-bound science.