The US Contribution to ITASE

US involvement in ITASE is consistent with the priorities established in numerous national and international science plans (e.g., Ice Core Working Group, 1987, 1988, 1989; Polar Research Board, 1986; WAIS, 1990, 1995; IGBP, 1990) that emphasize the need for extended spatial coverage of ice cores in Antarctica, intercalibration of ice core records and enrichment of resultant interpretations. In addition, consistent with the intent of objectives established in NSF's Supplemental Environmental Impact Statement for the United States Antarctic Program (SEIPS, 1990), ITASE will provide an environmental framework from which to assess change. Further, the aims of ITASE closely parallel the objectives of NSF's Global Change Research Program, which emphasizes the need for the collection of paleoclimate records, understanding ocean-atmosphere-land-ice interactions, and scaling of dynamic behavior and biogeochemical cycling.

US ITASE is an effort to organize a US contribution to the international ITASE program. Over the course of a two-day workshop (May, 1996) in Baltimore, Maryland, 37 participants (Appendix A) formulated the focus for US ITASE in West Antarctica, a site of major US glaciological activity for more than a decade. Research to date has addressed the question of the stability of this marine-based ice sheet (and implications for changes in sea level) under warmer climates such as the last interglacial period ~130,000 years ago (e.g., Scherer, 1991; Burckle, 1993) and the 2xCO2 atmosphere predicted for the next few decades (e.g., Bentley, 1980; Alley and Whillans, 1991; Bindschadler, 1991; Boyle and Weaver, 1994; Broecker, 1994a,b; Rahmstorf, 1994). The West Antarctic Ice Sheet Initiative (WAIS), a multi-disciplinary initiative (WAIS, 1995), is now in place with the goal to predict the future behavior and potential collapse of the West Antarctic Ice Sheet. The primary objective of WAIS is to understand the current state, internal dynamics and history of this environmental system (WAIS, 1995). To this end a broad range of geophysical and modeling studies has been undertaken (e.g., the Siple Coast Project, which grew into the WAIS initiative, focusing on West Antarctic ice streams that enter the Ross Embayment) as have reconnaissance activities focused on documenting the geophysical and glaciochemical characteristics of sites in West Antarctica from which long environmental records in the form of ice cores can be recovered. Two sites in West Antarctica (Siple Dome and inland WAIS; Figure 1) have been identified for the retrieval of such ice core records under the WAIScores component of WAIS.

As a component of WAIS, the US ITASE effort envisions a four-phase approach that will link modern meteorological and remote sensing studies for: (1) ground-based sampling (ice cores, radar and surface sampling), (2) continued monitoring (meteorology and ice dynamics), and (3) interpretation and modeling through the investigation of four research regions or corridors (Figure 1). US ITASE research projects are intended to complement and support each other to produce a better spatial and temporal understanding of climate and ice sheet behavior over the past 200+ years.

The concept that was favored at the Baltimore workshop both by the scientists and by the NSF delegation attending the meeting was to keep the logistical impact and the science budgetary impact modest by spreading research out over a number of years, while maintaining a strong focus on goals and interdisciplinary coordination. In this sense, the program provides another level of coordination and collaboration among disparate projects that are already planned or underway in West Antarctica, with the addition of new elements that the coordinated planning process has identified as critical to the overall 200-year climate study goals. US ITASE is intended to act as a scientific glue for these projects.

Ground-based sampling in each US ITASE corridor will focus on the collection of ~200-year-long ice cores at approximately 100km intervals. However, the ice cores are not the only component of US ITASE. Complementary studies in meteorology, remote sensing, and surface geophysics will be integrated with the coring program, and the concept of research in corridors is expected to be open-ended, depending only on the quality of the scientific questions proposed for investigation. For example, the goal of a 200-year climate history could be extended at selected sites to include longer time periods, and lateral sampling may be expanded along portions of the corridors to address questions related to surface geophysics and ice dynamics. Multi- disciplinary studies in the various corridors may take place over a time frame of several years. Experiments not included in the ground-based sampling may have additional opportunities to share logistics with other ongoing studies at a later time. For example, geophysical experiments such as GPS ice motion studies or borehole temperature logging will require multiple visits, spread out over several years, to research sites.