Recommendations for a
U.S. Ice Coring Program
Elements of an Ice Coring Program in the United States
OUTLINE OF REQUIREMENTS
The essential ingredients for a successful ice coring program, together with an assessment of their respective current strengths in the United States, include the following:
- Equipment for obtaining high-quality ice cores from suitable locations, regardless of depth (currently weak for depths exceeding 300 m).
- Capability for logging (moderately strong) and selective on-site analyses of ice cores (weak).
- Capability for laboratory analysis of a broad range of ice core properties (moderately strong).
- Transportation, storage, and distribution of ice cores (moderately strong).
- Personnel with scientific and technical knowledge and motivation who are committed and willing to participate in the field and guide the research to successful completion (inadequate numbers).
- Logistic structure for deploying hardware and personnel to the best drill sites (strong).
- Organizational structure that promotes accessory geophysical and other studies needed for site selection and interpretation of core stratigraphy (strong); coordination of scientific and technological development requirements (weak); international cooperation, which optimizes scientific output (strong); and extensive utilization of the results of ice core studies in associated fields (strong).
The importance and interdependence of these requirements are discussed below; specific steps to strengthen certain areas are recommended.
ICE CORING CAPABILITIES
The most immediate way the United States can strengthen its ice coring capabilities is to modify existing intermediate ice corers or build new ones to operate in fluid-filled holes. This appears to be the best practical means for achieving good core quality in the intermediate depth range and will extend the usable depth of light weight intermediate coring capability. This approach can proceed without major changes in existing winches, cables, and other surface support, although the use of hole fluid entails additional logistics. It is also the next logical step in the development of a deep drill.
Development of a deep drill in the United States would bring, scientific benefits in much greater proportion than its incremental cost, when scaled by present expenditures in the polar regions. Without a deep drill, the United States will continue to play a secondary role in the study of pre-Holocene ice. The cost of drill development, although substantial, is small compared to the total logistical effort of fielding a deep drilling operation. In this regard, a deep core drill may be regarded as a "logistics vehicle" for access to the interior of the ice sheet similar to transportation vehicles moving on or over the surface of the ice sheet. The cost of the drill should be considered in comparison with these other vehicles. The development of a deep drill would represent a step toward a long range U.S. commitment to ice coring. This would promote a commitment by U.S. laboratories to ice core research and would augment the U.S. scientific contribution to the international effort required in a major coring program.
Drill construction should be based on the most current technology and a thorough assessment of past and present coring experiences in the United States and other countries. Capability should include penetration to the deepest ice in Antarctica. The design should also attempt to incorporate a capability to penetrate moderately dirty ice near the bed at least as well as the current Danish drill, but preferably as well as the drill used at Camp Century (see Appendix B). If it is technically possible, without undue burden of cost to achieve a capability for penetrating sub-glacial material (both consolidated and unconsolidated and frozen and unfrozen), this should be implemented--as long as it does not compromise the drill's overall efficiency and utility for core collection in the ice column. Samples and probes to study the basal zone are needed to study important unresolved questions in ice dynamics.
In view of the scientific and technical coordination required to achieve a balance between scientific requirements and technological limitations, it is important that these drill developments are carried out by a group or groups closely tied to research laboratories and optimally, although not necessarily, to core storage.
ICE ANALYSIS TECHNIQUES
It is important to update existing U.S. lab facilities to increase the efficiency of ice sample analysis. This should include oxygen isotope analysis, microparticles, and especially accelerator mass spectrometer measurements. The United States should continue to develop capabilities for measurements of gases including chemical and isotopic composition, such as oxygen isotopes of the trapped air (Bender and others, 1979) and climatically active trace gases (Kahlil and Rasmussen, 1983a, b). Ion and trace chemistry, radioactive isotope chemistry and dating, and studies of physical and mechanical properties are also important to promote. There may be other opportunities to exploit.
Dry gas extraction techniques must be developed in the United States. This is essential for study of trace gas concentrations in the prehistoric atmosphere. Recently there has been great focus on the concentration and isotope composition of C02 in ice core gases. The major contributions have been made by groups in Bern and Grenoble, who have developed methods for the dry extraction of gases from ice (Berner and others, 1980; Delmas and others, 1980; Neftel and others, 1982; Raynaud and Barnola, 1985; Neftel and others, 1985b). While the trends of C02 concentration with time from ice age to present measured by the two labs are in agreement, there is a disagreement about the preindustrial level. This points to the difficulty of measuring the minute amounts of C02 trapped in the ice and relating this to the former atmosphere composition. There is a need for additional examination of these problems (see Appendix D). Furthermore, dry gas extraction may open up research frontiers in the study of other climatically important trace gases such as nitrogen oxides and fluorocarbons. It is also important to increase the emphasis upon on-site core handling and measurement techniques and participation in the field work by lab personnel. Initial logging of visible stratigraphy, profiling of solid surface and liquid melt conductivity, and core splitting and packing are essential steps in core recovery. The researchers working in the field effort will naturally have the best access to the core. At the Dye 3 site it has been demonstrated that experimental data on various chemical, physical and mechanical parameters of core ice can be readily obtained in field laboratories (Langway and others, 1985). Development of techniques that allow the most essential information to be gathered on-site without transport of solid core away from the site could promote a major revolution in coring programs because of the consequent reduction in logistics.
SUPPORTING MEASUREMENTS AND MODELING
A deep core drilling, project must be supported by ancillary measurements and analysis. Foremost among, these supports are those needed for selection of a site with a maximum potential and a minimum of complexities to confound interpretation. It is essential to conduct radar sounding to establish surface, bed, and internal layer geometry; motion measurements to establish flow patterns; and mass balance measurements. These must be at a spatial density much higher than is typical of reconnaissance surveys. The data should be fed into mass and heat flow models to determine what complexities might exist in the subsurface flow and to verify that large amounts of the oldest ice near the bed have not been melted off the bottom. Data from pits, shallow and intermediate depth cores should be gathered from an array of locations around a proposed deep) drill site to establish regional stratigraphic continuity and gradients in relation to current climate.
These necessities have long been recognized and criteria for assessing the suitability of a core site have been carefully considered in detail (Dansgaard and others, 1973; Langway and others, 1985). However, up to now core sites have been chosen primarily by logistical considerations, rather than by optimal scientific judgments. This is to be expected in the difficult circumstances of the polar environment. Some important questions cannot be answered at any existing stations. it is now time to exploit the scientifically optimal sites and design the logistics to make this possible. Because of the immense logistical problems and consequent expense, an orderly, measured schedule should be designed to maximize the information required for final site selection.
Once the large investment has been made to obtain a core, it is important to make as many useful measurements in the borehole as possible. Borehole logging measurements including vertical straining, hole tilting, ice temperature and acoustic and electrical properties all provide important information about the physical state of the ice necessary for understanding the ice sheet dynamics and for remotely sensing its interior and base. These data contribute to the interpretation of the stratigraphy measured in the core, and help identify changes caused by ice deformation. The U.S. capability in these areas is already fairly strong. It needs to be maintained by continued development of advanced techniques.
Ice flow modeling to establish the distribution of finite strain, origin position, and age along the core length is essential. Ice flow and temperature modeling directed specifically at ice core analysis is not highly developed anywhere, but there are productive efforts in a number of countries including the United States. This is an area the United States can easily advance.
ICE CORE STORAGE
The handling and storage of ice cores is another key element requiring coordination. The physical condition of a core is subject to change with time as a result of stress relaxation upon removal from the depth of the ice sheet, diffusion process when the temperature is near the melting point, and thermo-elastic stressing from temperature cycling of the aggregate of anisotropic ice crystals. These may also have chemical consequences especially if there is microcracking, which provides pathways for escape of sample gases and introduction of contaminants. Strategies for minimizing these effects must be kept in mind.
In some circumstances multiyear on site storage of parts of ice core should be considered. Successful onsite storage would require special procedures to minimize loss of core quality and to maintain accessibility in spite of burial by accumulating snow. From a logistical point of view, onsite storage might be advantageous by allowing an opportune time stepped transport of the massive weight of the ice cores. It would also provide a repository of ice that could be later retrieved without a new coring effort, for example to take advantage of new more advanced measurement opportunities. There is now much valuable ice core stored at Vostok, which is providing a resource for Soviet scientists working in collaboration with the French.
SCIENTIFIC INTERFACES AND PLANNING
There are important needs for scientific interfaces between ice core researchers and others focusing on paleoclimate data. These interfaces are needed not only for optimum scientific utilization of ice core data, but also to promote development of the most forward looking measurement and interpretation techniques and perspective in scientific planning. For example, a global strategy of ice core drilling, like the strategy involved in deep ocean floor drilling, is required for any large scale ice core program in order to obtain the maximum scientific results. Unlike the situation for ocean floor drillers, the locations of sites available to ice drillers is not almost unlimited. Only a small number of nonpolar ice caps, the relatively small Greenland ice sheet and the much larger Antarctic ice sheet, are available. But even for these ice masses there arc, depending upon the most immediate outstanding scientific questions, very bad choices and very good choices for site locations. These decisions necessarily involve the glaciological community, for example, to assess site suitability in terms of ice dynamics, preservation of stratigraphy, or other factors. However, at any given time the decision about whether to core in Greenland, Antarctica, or nonpolar regions as the next step must be based on a perception on how the results will be integrated into the outstanding problems in climate reconstruction and dynamics.
Past U.S. scientific research on ice cores from polar ice sheets has been carried out by individual scientists at different universities and government laboratories. Because of the diverse skills needed for obtaining the maximum information from ice cores, it is realistic to expect that the most qualified researchers on ice cores will always be spread out among a number of institutions. However, a dynamic, integrated scientific interpretation of ice core data is promoted by a close synergistic working relationship between scientists from various disciplines. Strong cooperation between the research scientists, the engineers who develop ice core drilling equipment, and the operators of this equipment is also important. The recent success of Danish and Swiss scientists is in part based on such a closely knit working relationship between people performing these three roles. In these groups some individuals play two or three roles. The fact that some of the U.S. efforts in ice coring have lagged behind those in other countries may in part arise from the splintered approach in the United States.
It is recommended that the future management of the U.S. ice core program be structured so that positive coupling factors are built-in to insure closer interaction between the different investigators as well as between scientists and engineers who have responsibility for drilling operations and drill equipment development.
This may be achieved in two stages.
(1) The first stage is of approximately one- to two- year duration. The operating mode will not be substantially different from the one used at present. A scientific plan (developed from National Research Council committee reports, NSF sponsored workshops, and the like) serves as the basis for invitations for proposals from individual university and government investigators. The best proposals are selected in the customary method by the granting agencies. If necessary, a second call for proposals is then made to ensure, if possible, that important research problems are not neglected.
During this initial stage it is expected that researchers who intend to participate in the ice coring field will develop close working relationships with colleagues at sister institutions. These relationships will be necessary in the second stage.
(2) In the second stage the granting agencies will request multi-institutional proposals. The second stage will start within the second or third year and will continue for the next decade. Although individual proposals will continue, a substantial fraction of the potential research funds will be earmarked for large multi-investigator proposals from a number of institutions. The primary research that will be carried out on ice cores will develop from these proposals. Science committees, both national and international, however, will continue to identify the most important scientific problems and to develop scientific plans for attacking them.
It is anticipated that in the second stage:
- Some institutions will increase their strength in polar ice core research.
- These institutions will become the leaders in developing polar ice core multi-institutional programs. At these stronger institutions, it is hoped that it will become easier for "new blood" to enter the field. The establishment of a capable personnel pool is one of the major requirements of the program. The "leader" institutions might logically develop at those places willing to take on ice core drilling development and the setting up of ice core repositories.
- Senior researchers involved with the analysis of ice cores (at all institutions) will be at field sites during periods when ice cores are first collected and initially examined before being transported to core repositories. This ensures that timely decisions by experienced scientific workers can be made about unexpected opportunities (or to minimize the impacts of setbacks).
Modern computer-based communication systems and a carefully considered data management program can aid greatly in producing a close interaction between researchers at distant locations. This should be exploited to the fullest in order to minimize the problems associated with the geographic spread of institutions in the United States. This has already been used with substantial benefit for international communication between Bern, Copenhagen, and Buffalo in GISP I.
Research institutes outside of the United States have played a major and often dominant role in ice core research in the last decade or more. A strengthening of the U.S. ice coring program will be promoted by continued and increased close interaction with these groups through international cooperation. This may proceed along currently established lines, but with some modification. First, there must be a better mechanism to represent the interests of U.S. scientists. In the past this has been done by the DDP program manager, but such dependence upon a single individual is unwise. Second, while the U.S. must expect to remain the principal provider of heavy logistics in international field efforts, future U.S. funding of the science effort should more strongly emphasize development of scientific capabilities within the United States.
It would be unfortunate if the present, somewhat inadequate, pace at which ice core data are generated by all of the world's scientists were to be significantly slowed because of reduced U.S.-international cooperation and funding. The international community in polar ice coring work has a splendid record for scientific and technical cooperation and funding. The collaborative involvement of SUNY, Buffalo with European labs in every aspect of GISP I is a good example. A strengthened U.S. ice coring program should continue in this tradition. Major ice coring efforts can only be mounted successfully with a multinational effort.
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