We must understand the climate system if we are to predict climate changes. The causes and mechanisms of past climate changes can be learned from careful paleoclimatic study. Ice cores are especially valuable, because they sampled the paleoatmosphere directly, and because they can provide exceptionally high time resolution over the critical period from the most recent ice age to today.
Key questions that must be answered about the climate system include: How rapidly has climate changed? Have changes been global or local? Have all climate variables changed at the same time, or were there leads and lags? In particular, have changes in temperature begun before or after changes in greenhouse-gas concentrations? Are large climate changes primarily linked to the smooth, periodic variation of Earth's orbital parameters, or are sudden `mode flips' more important? These and many other questions cannot be answered fully without analysis of carefully selected ice cores. These cores must sample ice-sheet regions near both poles where melting has not occurred, must have annual resolution from the most recent ice age to today, and should sample regions with simple ice flow to allow easy corrections for dynamical effects. More than one core is needed near each pole, to separate local from regional effects and to document these effects at key scales of space and time.
U.S. and European teams are drilling such ice cores in Greenland. However, no long, highresolution records have been collected in the southern hemisphere. Records based on studies of existing Antarctic ice cores are insufficient in scope, and ice in archives will not suffice to answer fundamental questions. Here, the U.S. Ice Core Working Group presents a science plan for WAISCORES (West Antarctic Ice Sheet Cores), a project to collect two critical southernhemisphere cores.
A high-resolution, long record from a southern-hemisphere region with simple ice flow is only possible in restricted areas of inland West Antarctica (Figure 1). We identify the most favorable area and outline a site-selection program to choose a drill site for deep coring inland. We discuss necessary investigations and outline field and analysis plans, with a timetable.
A core through an ice sheet necessarily samples a flowing ice mass, so we must understand ice-sheet changes to allow confident core interpretation. We recommend that a second West Antarctic core, which is needed to assess the regional significance of the first, inland core, be located to provide information on ice-sheet changes as well. We also recommend that paleoclimatic investigations be integrated with ice-dynamical studies to increase the scientific return from the project. As an added benefit, this will contribute important results to the question of West Antarctic ice-sheet stability and its effect on global sea level.
The WAISCORES Project proposed here is of global importance. The scientific and logistical capabilities of the U.S. community are adequate to complete this project. If sufficient funds are secured, execution of this science plan