Science and Implementation Plan: Executive Summary

The goal of the revised West Antarctic Ice Sheet Initiative (WAIS), formerly called SeaRISE, is to answer two critical and interrelated climate questions:

• How will the potentially unstable West Antarctic ice sheet affect future sea level?
   
• How do rapid global climate changes occur?

The West Antarctic ice sheet is the largest remaining marine ice sheet (those that are grounded well below sea level). Other marine ice sheets existed in the Northern Hemisphere during the last glacial maximum but all collapsed during the current interglacial. The sea-level record shows that ice-sheet collapse raises sea level at rates at least 30 times faster than what has been experienced in the last 4000 years. These collapses probably coincided with episodes when icebergs littered the North Atlantic Ocean, cooling the climate and disrupting global oceanic circulation.

The West Antarctic ice sheet contains enough grounded ice to raise global sea level 5 meters, were it to collapse into the ocean. Its deep, basin-shaped bedrock floor has the geometry appropriate for hosting an unstable ice sheet. Recent measurements show the ice sheet is currently undergoing rapid and dramatic change in particular regions and reveal a history of dramatic fluctuation in extent and size. Whether these changes are manifestations of natural short-term variability or impending collapse is not known, but these results require a fuller understanding of the nature of marine ice-sheet flow and demand a more com-prehensive assessment of the potential for triggering globally significant changes.

Because the flow of a marine ice sheet is strongly affected by the interactions of its ice streams and ice shelves with the surrounding terrestrial, oceanic and atmos-pheric environments, the research program described herein necessarily incorporates the coupled atmosphere-ocean-cryosphere-lithosphere system. Any prediction of West Antarctic ice-sheet behavior requires an understanding of the current state, history, internal dynamics, and mutual interactions within the polar atmosphere-ocean-cryosphere-lithosphere environmental system and its coupling to global climate.

The second WAIS question addresses a second, but equally significant, climatic role of West Antarctica as the site of a critical record of climatic history. Analysis of the ice cores from the summit area of the Greenland ice sheet has fundamentally revised the view of how rapidly large changes in climate have occurred and, presumably, can occur in the future. A question that must be answered is whether these climate switches apply to local climates only, or whether they extend globally. The answer to this question lies encased in the West Antarctic ice. Here the annual snowfall is larger than at any other Antarctic flow center. High accumulation rates are essential for the resolution of past annual layers, which is critical to determining absolute dating between cores, the response time of changes, and the phasings of key climatic parameters.

A second lesson from Greenland, and one that unavoidably links the two overarching WAIS questions, is the recognition that ice dynamics has an important influence on core stratigraphy-even at an ice divide. Synchroneity between the Greenland cores, drilled only 30 kilometers apart, completely disappeared when the Eemian Interglacial period was reached. This disturbing revelation forces a more complete charac-terization of flow and flow history at the site of any future ice cores.

Thus, WAIS is a multi-disciplinary study whose aims are to understand the nature of marine ice sheet flow, to decipher the climatic record contained within the West Antarctic ice sheet, and to assess its potential for changing sea level in the future. It seeks to accomplish this by focusing on three fundamental objectives:

Determine the current behavior and configuration of the West Antarctic environment, including ice-sheet geometry and kinematics, atmospheric circulation patterns and precipitation rates, lithospheric composition and distribution, and oceanographic circulation and heat transport;

Determine the physical controls on the ice motion, particularly the ice streams, how these processes are coupled to the atmosphere, lithosphere and ocean, and what aspects of this linked system drive the system toward or away from stability;

Determine the histories of the climate forcing and of the ice-sheet response in West Antarctica, including possible collapses, over the past glacial/interglacial cycle, and the phasing of these histories with those in the northern and southern hemispheres.

WAIS began in 1990, but has drawn heavily from a heritage of formerly unconnected disciplinary investigations. The original WAIS Science Plan described the key questions that must be answered within each discipline to attain the WAIS goal. This revision updates that description. As WAIS has continued, the ability of the involved scientists to exchange and share information beyond disciplinary boundaries has progressed. This maturation has resulted in the formulation of this revision to the WAIS Implementation Plan that truly exhibits the multidisciplinary character of WAIS. The revised Implementation Plan provides a status report of what is now known relevant to the WAIS goal, describes questions that still must be answered, and identifies the most urgently needed research. This portion of the document is intended to provide a guide to those wishing to propose new research and to answer NSF's request for a more realistic guide to the most important near-term requirements of WAIS. It is anticipated that the Science Plan will not require frequent revision, while the Implementation Plan, providing the current status and the short-term focus of the project, will be revised annually.

An expected time of completion is dependent upon the level of funding support. A minimum time for the completion of the required two ice cores and the initial analysis is seven years. Continued analysis and the development of sophisticated numerical models to incorporate the essential physics will extend the full length of the project, to beyond a decade.

WAIS also has a vigorous educational and public outreach program. Through the WAIS Working Group, it also will continue to foster interactions with international programs such as the Filchner-Ronne Ice Shelf Programme, the International Geosphere-Biosphere Program, and the International Trans-Antarctic Scientific Expedition, as well as related domestic programs such as NASA's Earth Observing System, to maximize scientific gain.