 |
 |
Articles | Documentation | Past Meetings | WAIS Working Group | Bibliography | Links |
Documentation |
|
Program Overview and Guide to this Site 
WAIS Illustrated Summary (with some figures) (October 1994)
WAIS Science and Implementation Plan (September 1995) |
WAIS Summary(October 1994) IntroductionThe West Antarctic Ice Sheet (WAIS) initiative is a coordinated, multidisciplinary research program designed to answer two critical, interrelated climate questions:
Future Sea-Level RiseThe 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.
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 ChangeA 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 those changes.
A Linked StudyWAIS 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 concerns.
A Systems ApproachWest 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 Nin–o 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.
The PresentWest 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.
The PastWest 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.
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.
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 today's configuration.
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. The FutureKnowledge 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. Science PlanWAIS 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. AccomplishmentsVigorous 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. EducationAntarctica 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 CooperationWAIS 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 Programme. 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 TimetableThe 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). |
| Home | Articles | Documentation | Past Meetings | WAIS Working Group | Bibliography | Links |
||
 |
Privacy, Security, Notices (opens in a new window) |
|