Program Overview and Guide to this Site
WAIS Illustrated Summary (with some figures) (October 1994)
WAIS Science and Implementation Plan (September 1995)
The West Antarctic Ice Sheet (WAIS) initiative is a coordinated, multidisciplinary
research program designed to answer two critical, interrelated climate questions:
- How will the unstable West Antarctic ice sheet affect future sea level?
- How do rapid global climate changes occur?
Future Sea-Level Rise
The West Antarctic ice sheet contains more than 3.2 million cubic kilometers
of ice and is the last ice sheet on Earth resting in a deep marine basin.
Ice-flow theory tells us that marine-based ice sheets are inherently unstable.
We know all other marine-based ice sheets completely collapsed during the
current interglacial beginning 20,000 years ago including a series of partial
collapses by the West Antarctic ice sheet. Marine records show that sea-level
rise during this period was punctuated by numerous episodes of very rapid
rise, many times faster than the rate over the last 4000 years. These jumps
in sea level are most probably the result of complete or partial ice-sheet
collapses. Complete collapse of the West Antarctic ice sheet would rapidly
raise global sea level an additional six meters-an event that has happened
at least once since the ice sheet formed.
|Sea-level history of Galveston Bay and Barbados (from Anderson, J., in prep. and Fairbanks, R. Nature, 342, 637-642 ).
Ice-sheet collapse would have a severe deleterious impact on existing estuarine
systems worldwide and possibly disrupt global oceanic circulation patterns,
triggering further climate change. The enormity of recent coastal development
radically alters the modern repercussions of climate change and rapid sea
level rise-50% of the U.S. population resides in a coastal zone, extending
more than 12,000 miles and valued at more than two trillion dollars! Even
today's modest rate of sea-level rise is rapidly driving shorelines inland
over many low-lying coastal areas. The societal risks of accelerated sea-level
rise escalate as the warming of today's interglacial period and sea-level
both continue to increase. We must learn what triggers marine ice-sheet
collapse and evaluate the probability of such a calamity.
Rapid Climate Change
A staggering result from analysis of the Greenland Ice Sheet Project-2 (GISP-2)
ice core was that regional climate can flip modes (from glacial to interglacial
conditions) in as little as a single year. These climate changes were more
profound than any in recorded human history, vastly exceeding, for example,
the Little Ice Age, which peaked in the mid-1730s and caused extensive abandonment
of farms in northwestern Europe as well as severe human problems elsewhere
around the world. A similar ice core from the Southern Hemisphere is urgently
needed to determine whether these rapid changes extended globally. The ability
to resolve annual layers in these cores enables scientists, for the first
time, to identify the precursory climatic parameters and the response time
scales of other parameters. The only area for a core capable of providing
a long annual-resolution history of Southern Hemisphere climate lies in
the interior of West Antarctica, where compressed snow layers are thick
enough to allow absolute dating of annual signals. Separating causes from
effects points scientists toward the mechanisms responsible for rapid climate
change and is a crucial step in the development of a predictive capability
to anticipate future climates and to mitigate undesirable consequences of
|Rapid change in accumulation rate in GISP2 core
(from Alley, R. et al., Nature, 362, 527-529 ).
A Linked Study
WAIS addresses both sea-level and climate concerns because knowledge of
the West Antarctic climate and the dynamics of its ice sheet are required
to address either issue. In addition to the paleoclimatic record, analysis
of ice cores yields a history of ice-sheet elevation, a parameter that determines
the forces driving ice-sheet flow. Correspondingly, the history of the ice-sheet
flow is a necessary part of the ice-core analysis, as the Greenland experience
clearly demonstrated. Thus, by linking the questions and coordinating the required investigations,
many of the same measurements can be applied to address two pressing climate
|Folds in GISP2 ice core (photograph courtesy of R. Alley).
A Systems Approach
West Antarctica is a tightly coupled environmental system with strong connections
to global atmospheric and oceanic circulation patterns. Regeneration of
the ice sheet depends upon delivery of moisture from various source regions
carried by atmospheric circulations that reflect global rhythms, such as
the El Nino Southern Oscillation. The ice sheet is drained by rapidly moving ice streams sliding on extremely
weak marine sediments deposited during periods of ice-sheet absence. The
active rift system underlying the ice sheet permits enhanced heat flow to
melt basal ice, weakening the subglacial strata and further lubricating
the subglacial interface. Huge floating ice shelves impede ice-stream drainage,
and circulations in the water cavity beneath the shelves deliver heat from
the open ocean to the undersides of the ice shelves. If enough heat is supplied,
ice shelves will corrode from underneath much faster than they can be supplied
by snowfall. The elimination of ice shelves leads to collapse of the ice
sheet in some models.
|Depth profile of methanesulphonic acid (MSA)
from Antarctic ice core with occurrences of
El Nino-Southern Oscillation (ENSO) events
indicated by letters (W: weak,
M: moderate, S: strong and VS: very strong)
(Isaksson, E. et al., in prep.).
West Antarctica is changing rapidly in many areas. The flow of ice stream C completely stopped approximately 150 years ago,
while its neighbor, ice stream B, is discharging 50% more ice than it receives
in snow accumulation. Elsewhere, the flow of Thwaites Glacier is accelerating,
while ice in the mouth of ice stream B is decelerating. Complex features
abound which illustrate that the ice sheet is in a non-equilibrium state.
Whether this complex pattern is symptomatic of impending collapse is not
known. No consistent pattern has yet emerged but many regions await assessment.
|Rates of ice-thickness change calculated for regions drained by ice stream A - F, West Antarctica, superimposed on a mosaic of Advanced Very High Resolution Radiometer (AVHRR) imagery.
West Antarctica is replete with evidence of its ice-sheet's dynamic history.
Geologists identify and date past ice-sheet surface elevations and flow
directions from features preserved on the mountains protruding through the
existing ice sheet.
|Trimline (arrow) of former ice sheet in
Sentinel Range, West Antarctica
(photograph by C. Craddock).
Marine geophysicists probing the sediments in the West Antarctic seas discern
a rich history of repeated advances to the very edge of the continental
shelf followed by retreats to and past the modern position.
|Seismic section of Ross Sea bed
showing till-delta stratigraphic sequence
created by mulitple advances of the
West Antarctic ice sheet. Paleo-flow
is from right to left (Anderson, J. in prep.).
Remote sensing and field measurements through the existing ice reveal evidence
of past disappearance of the ice sheet and supply geologic specimens that
connect the records of terrestrial geology and marine geology. These data
leave no doubt that the West Antarctic ice sheet has been both much larger
and much smaller than we find it today. Models incorporating a simple interplay
between the atmosphere, ice and marine bed demonstrate the unstable nature
of West Antarctica as it oscillates between its extreme states. Possible relict ice-stream margins exposed by satellite imagery hint that
the existence and locations of past ice streams varied substantially from
|Simulated history of West Antarctic
ice-sheet volume calculated by a coupled
basal-till/ice-flow model (MacAyeal, D.,
Nature, 359, 29-32 ).
The interpretation of the ice core's paleo-climate record depends critically
upon an understanding of the ice sheet's dynamic history. Within the ice
core, the climatic and dynamic signals are combined. For example, temperature
changes inferred from the isotopic composition of the ice core can be due
to either climate changes or changes in the surface elevation. As a check
on the separation of these two signals, the elevation record must be consistent
with the shape of the ice sheet deduced from geologic data and the climate
record must be consistent with the pattern of atmospheric circulation that
is influenced by the ice-sheet shape. Simultaneously addressing both questions
is mutually beneficial.
Although longer Southern Hemisphere climate records can be obtained from
deeper ice in East Antarctica, these cores lack the high resolution and
absolute dating needed to reveal and correlate the rapid fluctuations seen
in Greenland. Thus, WAIS ice core data will be uniquely able to answer whether
the climate mode-flips seen in Greenland are global and, if so, indicate
where they started and how they spread. Because the data will be linked
with an ice-dynamics history, scientists also will be able to answer whether
the mode-flips were a result of marine-ice-sheet collapse, or vice versa.
The continuous temporal record of surface elevation may either validate
or refute the hypothesis that the West Antarctic ice sheet disappeared during
the last interglacial-a long-standing belief of considerable importance.
Knowledge of the past will provide the keys to unlock the future. Models
are the tools. We require a better understanding of the physical processes
controlling ice stream motion including the role played by the heated subglacial
sediments, of the connection between the deep ocean and the sub-ice-shelf
cavity, and of the connection of global atmospheric patterns to the moisture
fluxes delivered to West Antarctica. The ability to reproduce historical
descriptions of West Antarctica validates the models and provides a means
for model improvement as the historical data set grows.
WAIS is a multidisciplinary program. The proposed investigations comprehensively
examine the ice sheet from ice divide to calving front, on the terrestrial,
subglacial and submarine surfaces where it is or has been, and in the proximal
and distant atmosphere and ocean. WAIS is clearly defined by a set of key
questions that serve to focus the scientific effort. These are listed in
the WAIS Science and Implementation Plan along with specific studies needed
to answer these key questions. The principal elements have already appeared
in this report.
Vigorous scientific activity is already underway in preliminary support
of the directions detailed in the WAIS Science and Implementation Plan.
This report is based largely on those recent advances. As we achieve a greater
understanding of the West Antarctic environment, it becomes increasingly
clear that a coordinated, multidisciplinary program is the most direct path
to achieving the WAIS goals of answering both the climate and sea-level-change
questions. Two workshops have fostered the interdisciplinary exchange of
information that has enhanced the WAIS effort. This exchange stimulates
an interplay between new results and planned investigations that maintains
a sharp focus on the WAIS goals.
Antarctica has always held the attention of the public because of its unique
characteristics; however, its immediate relevance to the climate of the
inhabited world is a recent revelation. In recognition of this, the WAIS
community has acknowledged an educational responsibility and explicitly
incorporated it into the organizational structure. A Working Group member,
with expertise in both science and education, is formulating specific programs
to increase the global community's awareness of WAIS research and to educate
its people in the ways in which West Antarctica-an often-presumed passive
and distant "ice cube"- affects their lives.
Inter-Agency and International Cooperation
WAIS provides compelling science research that addresses pressing global
climate issues. As such, it has attracted scientists from beyond academia.
USGS and NASA scientists are currently involved. WAIS conforms to front-line
scientific issues as determined by the U.S. Global Change Research Program
(including NASA's Earth Observing System), and the Scientific Committee
on Antarctic Research's (SCAR) role in the International Geosphere-Biosphere
The U.S. is in the strongest position to conduct WAIS by virtue of its existing
multidisciplinary involvement and utilization of advanced technology in
West Antarctica. The longer, lower resolution cores being collected and
analyzed by other countries in various locations throughout East Antarctica
will complement the WAIS cores, but they cannot determine the cause of rapid
climate-switching or the phasings between hemispheres. Another complementary
project is the Filchner-Ronne Ice Shelf Programme, which is strongly focused
on the ocean-ice interactions in the Weddell Sea sector where U.S. logistics
cannot easily support U.S. scientists. Finally, the proposed U.S. contribution
to the International Trans-Antarctic Scientific Expedition is in West Antarctica
and the set of shallow cores collected as part of that program will further
complement the understanding of the climate patterns in West Antarctica
sought by WAIS. Cooperation with scientists from all these other programs
is expected, but unless the U.S. conducts WAIS, critical Antarctic research
of vital global climatic significance will be left undone.
Budget and Timetable
The timetable is controlled by the sequence of events associated with a
major ice-core drilling program. Careful site selection is required to determine
the site containing the most detailed and least disturbed paleo-record.
Following a procedure proven in Greenland, site-selection programs are already
underway leading to a core to bedrock on Siple Dome in 1997-98 followed
by a three-season drilling campaign at the Inland ice-divide site in 1998-2001.
Extensive analysis of the ice core will continue for at least two years
beyond this date as more measurements are conducted at the National Ice
Core Laboratory. On the basis of extensive canvassing of the ice-core community,
the best estimate for the ice-core effort is $15M.
Additional funds are also required to support a broad suite of other WAIS
activities, beginning in Fiscal Year 1996. Many require field support and
every effort will be made to optimize logistic support by focusing on particular
areas in single years. The WAIS Science and Implementation Plan provides
a detailed 7-year scenario as a starting point for planning that is properly
phased with the requirements and anticipated results of the ice core and
associated efforts. The cost of these non-coring activities, also detailed
in the WAIS Plan, totals $51M-a total, 7-year cost of $66M.
Cover Photos courtesy of National Geographic Society (drought and New York
City), Time-Life books (ice front), and M. Twickler (ice core).