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International Trans Antarctic Scientific Expedition
In 1996 an NSF workshop was held to develop a Science and Implementation Plan for the United States contribution to ITASE (called "US ITASE"). Because of the long-standing U.S. research effort in West Antarctica, U.S. ITASE chose to focus its activities there. At the U.S. ITASE workshop, participants developed a multi-disciplinary research plan that integrates different approaches to environmental research: Meteorology, remote sensing, ice coring and surface glaciology, and geophysics. They established a plan with four phases:
• In Phase 1 meteorological modeling and remote sensing was used to plan sampling strategies in support of U.S. ITASE's major objectives.
• Phase 2 initiates ground-based sampling over four study areas (corridors). Notwithstanding the broad spatial sampling of West Antarctica proposed, the logistic requirements for this sampling will be modest and highly efficient.
• Phase 3 will continue ground-based sampling at a limited number of key sites where monitoring is required.
• Phase 4 entails data interpretation and modeling.
The United States component of ITASE (which has established a wide range of general scientific objectives) is trying to refine answers to the following questions:
• At what rate is the mass balance changing over West Antarctica?
• How do the major oceanic and atmospheric circulation systems (e.g., ENSO) influence the moisture flux over West Antarctica?
• How and why does climate (e.g., temperature, accumulation rate, atmospheric circulation) vary over West Antarctica on seasonal, interannual, decadal and centennial scales?
• What is the frequency, magnitude and effect (local to global) of any extreme climate events recorded in West Antarctica?
• What is the impact of anthropogenic activity (e.g., ozone depletion, pollutants) on the climate and atmospheric chemistry of West Antarctica?
• How much has biogeochemical cycling of sulfur, nitrogen and carbon, as recorded in West Antarctica, varied over the last ~200 years?
Radar studies of internal stratigraphy and bedrock topography along
the U.S. ITASE traverse.
The U.S. component of the International Trans-Antarctic Scientific Expedition (U.S. ITASE) conducts radar studies to determine the internal stratigraphy and bedrock topography of the terrain along the traverses. To help in the selection of core sites as the traverse proceeds, the radar provides information on ice thickness and internal layer structure that is immediately available to those working in the field. These data can also be used to site deeper millennial scale cores (planned at less frequent intervals along the traverse) and to provide a context for selecting the location of the deep inland core (planned for the future). In addition to mapping the traverse route, radar is used to examine a grid surrounding each of the core locations, to better characterize the accumulation and bedrock topography in each area.
This radar system works as a complement to that operated by the Cold Regions Research and Engineering Laboratory (CRREL). Theirs is a high-frequency radar, most suited to the shallower portion of the record down to approximately 60 meters (m); it can detect near-surface crevasses. Our radar system is most sensitive at depths below 60 m, able to depict deep bedrock and internal geological layers deep into the ice. (IU-133-O)
Science management for U.S. ITASE.
Coordinating the effort developed for the United States component of the International Trans-Antarctic Scientific Expedition (U.S. ITASE) is the Science Management Office (SMO). The broad aim of U.S. ITASE is to develop an understanding of the last 200 years of west antarctic climate and environmental change. ITASE is a multidisciplinary program that integrates remote sensing, meteorology, ice coring, surface glaciology and geophysics. To marshal this effort, SMO runs a series of annual workshops to coordinate the science projects that will be involved in ITASE. They also establish and operate the logistics base that supports ground-based sampling in West Antarctica. (IU-153-A)
U.S. ITASE glaciochemistry.
Among the research targets for scientists in the U.S. component of the International Trans-Antarctic Scientific Expedition (U.S. ITASE) are the impact of anthropogenic activity on the climate and atmospheric chemistry of West Antarctica, as well as the variations in biogeochemical cycling of sulfur and nitrogen compounds over the last 200 years. This 5-year project is conducting glaciochemical analyses of the major anions and cations to be found in shallow and intermediate depth ice cores collected on the U.S. ITASE traverses. The ionic composition of polar ice cores provides one of the basic stratigraphic tools for relative dating. Also, these data can be used to document changes in chemical-species source emissions, which in turn facilitate mapping and characterization of the major atmospheric circulation systems affecting the West Antarctic Ice Sheet. (IU-153-B)
Snow and firn microstructure and transport properties: U. S. ITASE.
Not all valuable data are buried deep within the ice. The microstructure and bulk properties of snow and firn near and at the surface control the air/snow/firn transport processes; i.e., how heat, vapor, and chemical species in air are incorporated into snow and polar firn. Since many of the snow and firn properties also affect the interaction of radiation in different parts of the electromagnetic spectrum, field measurements provide a valuable ground truth "check" for complementary efforts using remote sensing to map the spatial variations of snow, firn and ice properties.
This project does the field and lab work to characterize snow and firn properties along the U.S. International Trans-Antarctic Scientific Expedition (U.S. ITASE) traverses in West Antarctica. Our objectives are to obtain field measurements of near-surface [down to 2 meters(m)] snow and firn properties: Surface roughness, permeability, density, grain size, surface-to-volume ratio, and tortuosity. In the laboratory, firn cores from as deep as 20 m will be analyzed for these properties and for their microstructure. Ultimately, we will develop a transport model to elucidate the nature of the air/snow/firn exchange and firnification process at the various sites along the U.S. ITASE traverse. (IU-155-O)
Hydrogen peroxide, formaldehyde, and sub-annual snow accumulation
in West Antarctica: Participation in west antarctic traverse.
Atmospheric photochemistry leaves valuable traces in snow, firn and ice, and it has been verified that the efficiency of atmosphere-to-snow transfer and the preservation of these components is strongly related to the rate and timing of snow accumulation. Thus the firn, as well as the atmosphere, provides the context for data.
This project will collect samples along the U.S. International Trans-Antarctic Scientific Expedition (U.S. ITASE) traverses. The wide-ranging extent of these traverses will train the scientific lens upon a variety of locations covering much of the West Antarctic region and reflecting a range of different depositional environments.
Measurements of the concentration of seasonally dependent species (such as hydrogen peroxide, nitric acid, formaldehyde and stable isotopes of oxygen) will be made on these samples and fed into a recently developed, physically based, atmosphere-to-snow transfer model in order to elucidate the photochemistry that led to the depositons. (IU-158-O)
Mass balance and accumulation rate along U.S. ITASE routes.
One of the basic ways to deduce past climate variations is to track the accumulation of ice, which gives a measure of the balance of mass on the continent. Ice cores from the traverse routes of the U.S. International Trans- Antarctic Scientific Expedition (U.S. ITASE) program should provide a broad history of how West Antarctica has changed in this fundamental way.
This 5-year project is tracking the rate of ice sheet thickening/thinning along the traverses by looking at flow lines, ice divides and elevation contours. We will measure the vertical velocities of markers buried in subsurface ice, using the Global Positioning System (GPS) and surveying techniques to determine the precise location of these markers. As these markers move up and down, they provide a measure of the change in ice sheet thickness, when adjusted for the thickness of snow accumulation directly above them.
That can be accomplished through a series of recording instruments that provide continuous records of firn densification and snow surface elevation change. These altimeters measure the snow surface elevation transient changes, and provide the data necessary to deduce long-term change rates of ice thickness. The ice motion at drill sites, upglacier topography and upglacier gradients in accumulation rate will be measured and used to calculate iceflow-induced accumulation rate variations, which ultimately will refine the ice core records. (IU-178-O)
High resolution radar profiling of the snow and ice stratigraphy beneath
the ITASE traverses, West Antarctic Ice Sheet.
The U.S. component of the International Trans-Antarctic Scientific Expedition (U.S. ITASE) uses high-resolution radar profiling of the snow and ice stratigraphy beneath the traverse routes in West Antarctica. This project provides a complement to project IU-133-O [where levels below 60 meters (m) are the focus], concentrating on the shallower levels of the Earth. Excavating the traverses can be a hazardous undertaking, made much safer, however by the advanced crevasse detection capability of this system.
A coherent, short-pulse radar with a 400 MHz antenna will be the primary tool. The system allows real-time monitoring in a horizontally scrolled display, and provides exceptional vertical resolution – to an order of tens of centimeters – to a depth of 50 to 70 m. Analysis relies on simple data compression (stacking), which reveals subtle deformational features as well as long distance trends. Isochronal continuity will be interpreted from reflection horizons between core sites. (IU-311-O)
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