US Global Ice Core Research Program
West Antarctica and Beyond

4. US Ice Core Research Plan

US ice core research, encompassing a wide spectrum of capabilities (ICWG report, 1987), can fill important gaps in our knowledge of past and present environmental conditions. Below we present specific research objectives that address the important problems discussed above. An outline of a long-range plan to realize these objectives follows. This plan may require modification during execution based on results obtained by early studies and by our sister disciplines (e.g. ice dynamics, oceanography, atmospheric sciences, climate modeling), but should prove useful for guiding and encouraging ice core research.

4.1 Specific Objectives

a. Recover a long (up to 106 years), detailed record of natural climate and paleoenvironmental changes in both hemispheres.

Such a record will identify the major components of climate change (e.g. Milankovitch cycles) over several full glacial-interglacial cycles as wen as the fine structure of climate variability on a time scale of decades to millennia that is superimposed on the long-term variations under glacial and interglacial climate conditions. Comparison with the long ocean-sediment records and coral records may reveal ocean-atmosphere-cryosphere interaction.
b. Recover high-resolution records of the Holocene and the last interglacial transition from as many distinct geographical locations as possible.

Records with annual resolution will provide well dated and highly detailed histories of environmental change over decades to millennia. Time scales for the younger part of long records that lack annual resolution may be established by correlation with these high-resolution records. Accurate chronologies are needed to compare the timing of changes in ice cores, ocean cores, and terrestrial deposits from both hemispheres.

c. Determine cause and effect relationships between changes in climate and changes in atmospheric composition.

These may be determined from lag/lead phase relationships between changes in d180/dD and the concentration in the ice Of C02, CH4, 02, dust, major cations and anions, trace elements, cosmogenic isotopes, and other constituents. Of special interest are the rapid glacial to interglacial warmings, but also the Younger Dryas climate episode and the apparently rapid Dansgaard/Oeschger climate events documented in Greenland. Study of the "Little Ice Age" and other recent Holocene climate oscillations is important to understand perturbations of the interglacial climate and offers the best calibration of ice core records with instrumental and historical records.

d. Determine changes in global biogeochemical cycles, (e.g. carbon, oxygen, sulfur, and water) due to natural causes.

The carbon cycle can be monitored in the ice mainly by measuring C02, CH4, and CO concentrations and isotopes in air trapped in the ice. The concentration of these gases affects the radiative properties of the atmosphere. Their 13C/12C ratio also indicates redistribution of carbon between atmosphere, ocean and biosphere. Sulfur (as S042- or CH3SO3-) and its isotopic composition provide records of volcanic activity, meridional transport (in conjunction with major cations), and ocean productivity of dimethylsulfide (DMS). DMS is produced by phytoplankton in the surface ocean and is released into the atmosphere via gas exchange. In the atmosphere DMS is oxidized to sulfur dioxide, methanesulfonate, and ultimately, sulfate. The sulfate aerosol is the principal source of cloud condensation nuclei over the oceans and may play a major role in controlling the planetary albedo and, through it, global climate.

e. Determine natural changes in global tropospheric chemistry.

Global tropospheric chemistry may be affected by changes in the oxidative capacity of the atmosphere; most significantly by changes in OH, 03 and NOx. Measurements of CH3Cl (methylchloride), H2 (hydrogen), and of light hydrocarbons (C2-C4) are needed as indicators of possible changes in OH concentration.

f. Examine natural changes in global biogeochemical cycles of toxic species.

Toxic chemical species of many types are produced by human activities and may pose environmental hazards. Examples include heavy metals, hydrocarbons, and inorganic and organic acids. Many of these species also have natural sources. It is important to understand natural variations in environmental levels and in biogeochemical cycling of these species to provide a baseline to which current pollution can be compared.

g. Elucidate the interaction between climate, ice sheet size, and sea level.

The focus is here on the West Antarctic ice sheet because much of its bedrock is below sea level. This ice sheet may be prone to sudden decay as has been documented for the Laurentide ice sheet. The approximately 6m of sea level rise resulting from a collapse of the West Antarctic ice sheet would flood coastal areas around the world.

h. Improve our understanding of anthropogenic influence on global biogeochemical cycles and climate.

As the dynamics of natural biogeochemical cycling and natural variations in climate are unraveled from the ice core records, anthropogenic effects can be better defined. For example, comparing concentrations of certain chemical species in pre-industrial and modem ice will help determine the extent to which anthropogenic sources have perturbed natural biogeochemical cycling of these species and/or climate. This information is vital as input to models that predict ecosystem effects and climate change, and for helping decision-makers choose control strategies to limit pollutant emissions.

Properties that need to be measured to reach the objectives outlined above are listed in Appendix B.

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