This award provides funding for five years of support to participate in the U.S. component of the International Trans-Antarctic Scientific Expedition (US ITASE). US ITASE is made up of four major research disciplines: meteorology, remote sensing, ice coring, and surface glaciology and geophysics. US ITASE hopes to answer questions about the mass balance over West Antarctica and the influence of major atmospheric circulation systems and oceanic circulation on the moisture flux over West Antarctica. In addition, questions about the controls on climate variations over seasonal, inter-annual, decadal and centennial scales will be addressed. Other factors to be examined by US ITASE relate to 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 project will perform analyses of the glaciochemistry (i.e. major anions and cations) of shallow and intermediate depth ice cores collected on the US ITASE traverses. The ionic composition of polar ice cores provides not only a stratigraphic tool for relative dating but also documents changes in chemical species source emissions and allows characterization of the major atmospheric circulation systems affecting the West Antarctic ice sheet.
This award is for support for a Science Management Office (SMO) for the United States component of the International Trans-Antarctic Scientific Expedition (US ITASE). The broad aim of US ITASE is to develop an understanding of the last 200 years of past West Antarctic climate and environmental change. ITASE is a multidisciplinary program that integrates remote sensing, meteorology, ice coring, surface glaciology and geophysics. In addition to the formation of a science management office, this award supports a series of annual workshops to coordinate the science projects that will be involved in ITASE and the logistics base needed to undertake ground-based sampling in West Antarctica.
This award supports a project to measure snow and firn bulk properties and microstructure along the route of the U.S. International Trans-Antarctic Scientific Expedition (US ITASE) traverses in West Antarctica. These parameters are important because they control the air-snow-firn transport processes and thus the manner in which heat, vapor, and chemical species in air are incorporated into snow and polar firn. The objectives of the project are to obtain field measurements of near-surface (down to 2 meters) snow and firn properties, which include surface roughness, permeability, density, grain size, surface-to-volume ratio, and tortuosity. In addition microstructural measurements and measurements of the above properties will be measured in firn cores down to 20 meters back in the laboratory. These measurements will be used in 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. Since many of the snow and firn properties also affect the interaction of radiation in different parts of the electromagnetic spectrum, these measurements will provide valuable ground truth to those efforts using remote sensing to map the spatial variations of snow, firn and ice properties.
This award provides support for five years of funding to determine the mass balance and accumulation rate of ice along the traverse routes of the U.S. International Trans-Antarctic Scientific Expedition (US ITASE) program. The rate of ice sheet thickening or thinning will be measured along flow lines, along ice divides and along elevation contours in West Antarctica using a method which measures the vertical velocities of markers buried in subsurface ice. This method uses the Global Positioning System (GPS) and surveying techniques to determine the precise location of these markers. Vertical velocities so obtained are compared with long-term rates of snow accumulation and the difference in the two is a measure of ice sheet thickness change. A series of recording instruments will be installed to provide continuous records of firn densification and snow surface elevation change. These instruments will be deployed at selected sites to link transient changes in snow surface elevation, as measured by altimeters, to long-term rates of ice thickness change. Ice motion at drill sites, upglacier topography and upglacier gradients in accumulation rate will be measured and used to calculate ice flow-induced accumulation rate variations and remove them from the ice core records. This work will provide the capability to deduce true past climatic variations in accumulation rate from the US ITASE ice core records.
This award supports a project to improve understanding of atmospheric photochemistry over West Antarctica, as recorded in snow, firn and ice. Atmospheric and firn sampling will be undertaken as part of the U.S. International Trans-Antarctic Scientific Expedition (US ITASE) traverses. Measurements of hydrogen peroxide (H2O2) and formaldehyde (HCHO) will be made on these samples and a recently developed, physically based atmosphere-to-snow transfer model will be used to relate photochemical model estimates of these components to the concentrations of these parameters in the atmosphere and snow. The efficiency of atmosphere-to-snow transfer and the preservation of these components is strongly related to the rate and timing of snow accumulation. This information will be obtained by analyzing the concentration of seasonally dependent species such as hydrogen peroxide, nitric acid and stable isotopes of oxygen. Collection of samples along the US ITASE traverses will allow sampling at a wide variety of locations, reflecting both a number of different depositional environments and covering much of the West Antarctic region.
This award supports a program of radar studies of internal stratigraphy and bedrock topography along the traverses for the U.S. component of the International Trans-Antarctic Scientific Expedition (US ITASE). The radar will provide information immediately available in the field on ice thickness and internal layer structure to help in the selection of core sites as the traverse proceeds. These data will also be useful in siting deeper millennial scale cores planned at less frequent intervals along the traverse, and in the selection of the location for the deep inland core planned for the future. In addition to continuous coverage along the traverse route, more detailed studies on a grid surrounding each of the core locations will be made to better characterize accumulation and bedrock topography in each area. This proposal is complimentary to the one submitted by the Cold Regions Research and Engineering Laboratory (CRREL), which proposes a high frequency radar to examine the shallower portion of the record down to approximately 60 meters, including the presence of near-surface crevasses. The radar proposed herein is most sensitive at depths below 60 meters and can depict deep bedrock and internal layers to a substantial fraction of the ice thickness.
This collaborative proposal supports a project to perform stable isotope analyses of samples collected along the International Trans-Antarctic Scientific Expedition (ITASE) traverses which will begin during the 1999/2000 Antarctic field season. This work will focus on the spatial and temporal distribution of oxygen-18 and deuterium in West Antarctica (where data are particularly sparse) and the calibration of the isotope-climate relationship on a site-by-site basis, using instrumental and remote-sensing temperature histories. Specific objectives of this work which contribute to ITASE are: 1) to obtain detailed oxygen-18, deuterium and deuterium excess and stratigraphic histories in snowpits at most or all of the ITASE coring sites; 2) to provide direct calibration of the isotope-climate relationship at each site through a combination of direct (AWS) and indirect (passive microwave satellite) temperature measurements; 3) to obtain isotope profiles covering the last 200 years; and 4) to use the results to provide 200-year climate histories at high temporal and broad spatial resolution across West Antarctica that will allow testing of proposed relationships among isotopes, moisture source conditions, synoptic scale climatology, and site-specific meteorological parameters, and which will enhance our ability to interpret isotope records from older and deeper Antarctic ice cores.
This is a 4-year project to examine the visual stratigraphy, physical and structural properties of the U.S. ITASE ice cores spanning the last 200 years of snow accumulation in Antarctica. A first priority will be to examine visual stratigraphy to delineate annual layer structure for dating purposes and to determine to as great a depth as possible, accumulation variability over the full length of a stratigraphically dated core. A second objective will be to measure and analyze depth-density profiles. The rate of snow and firn densification depends on both the rate at which the snow is deposited and the in situ snow temperature. These data can and will be used to derive average snow accumulation rates for the sites where annual layer structure is difficult to decipher or where stratigraphic analysis fails altogether. A third objective will entail measurements of mean crystal size over the full length of a core. Crystal growth is a strongly temperature dependent process and measurements to be made on ITASE cores will help to bridge a significant data gap that exists in the mean annual temperature range, -31° to -50°C. Additionally, crystal size data can also be used, in conjunction with ice loads based on density profile measurements, to extract mean accumulation rates for these sites where stratigraphic dating of cores proves difficult or impossible to accomplish. This is likely to occur at the lowest accumulation/lowest temperature sites along the ITASE traverse routes.
Halogenated ethane derivatives (HFC, HCFC) have been introduced as environmentally friendly CFC substitutes. Trifluoracetate (TFA) is a highly persistent, atmospheric degradation product of these compounds and there is concern that the widespread introduction of HCFCs and HFCs will lead to the accumulation of TFA in aquatic ecosystems. Indeed, our pilot data on TFA deposition at South Pole indicate a significant increase in TFA deposition in the late 1990s. However, data on pre-industrial, background concentrations of TFA in meteoric and surface wasters are ambiguous and the impact of anthropogenic TFA on these background concentrations is unclear. We will develop a record of recent TFA deposition in Antarctica using surface-snow, snow-pit and ice-core samples collected at South Pole and, through participation in ITASE, in West Antarctica.