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United States Antarctic Research: Report No. 32 to the Scientific Committee on Antarctic Research (SCAR) 1 April 1989 - 31 March 1990 Prospectus Of Planned Activities 1 April 1990-31 March 1991 Atmospheric Sciences Ozone-Depletion Studies Polar stratospheric clouds at the South Pole James M. Rosen, University of Wyoming (S-117) The results of research since 1986 indicate that polar stratospheric clouds (PSCs) have a significant role in the annual springtime depletion of ozone above Antarctica. Scientists believe that these ice-crystal clouds, which form in the stratosphere at temperatures below -80°C, provide the environment in which the ozone-destruction cycle occurs. The objective is to study the physical, chemical, and radioactive properties of these clouds and the relationship between the clouds and the ozone-destruction cycle. To obtain data, 20 balloons carrying various instruments will be launched near Amundsen-Scott South Pole Station. The instruments will measure water vapor, ozone, temperature, winds, infrared heat flux, and on some flights, nitric acid vapor. A PSC-sonde will be used to detect the presence of polar stratospheric clouds and stratospheric aerosols and to provide information on particle size and distribution in the clouds. Data from these measurements will provide new details on dehydration and denitrification in the polar stratosphere. Springtime measurements of ozone-related compounds in the antarctic stratosphere David G. Murcray, University of Denver (S-270) The springtime decrease of atmospheric ozone over Antarctica has been observed over Halley Bay, Syowa, and South Pole stations and has been recorded by satellites over a wide area of the continent. Although current photochemical models did not predict these observations, atmospheric scientists now agree that chlorine chemistry has a major role in the decrease. The effects of other atmospheric constituents, however, are still unclear. In this study, infrared techniques will be used to measure the concentrations of compounds in the stratosphere over Antarctica. The field party will service the infrared emission interferometer at Amundsen-Scott South Pole Station; this equipment records infrared solar spectra during the winter. Solar spectra, which contain thousands of absorption lines produced by compounds present in the atmosphere, can provide information about atmospheric chemistry at the time that the measurements were made. Because they respond to molecules anywhere along the optical path, this technique yields information on the total column density of compounds present in the stratosphere. These data will be used to analyze for total-column density of hydrochloric acid, nitric acid, nitrogen dioxide, chlorofluorocarbon gases F-11 and F-12, ozone, methane, and nitrous oxide to document the changes in the amounts of these compounds from late winter through early spring. Investigation of polar stratospheric aerosols and their relation to the ozone hole David J. Hofmann and James M. Rosen, University of Wyoming (S-289) In this study, scientists hope to provide information valuable to two of the models proposed to explain the springtime ozone-hole phenomenon (the chemical model and
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United States Antarctic Research: Report No. 32 to the Scientific Committee on Antarctic Research (SCAR) 1 April 1989 - 31 March 1990 the dynamic model). Using balloonborne instruments, scientists will systematically study polar stratospheric clouds and related ozone variations. With data from earlier studies, it was established that polar stratospheric clouds are related to the annual appearance of the ozone hole. The locations in the air column where most of the ozone is being destroyed were identified. During the austral summer, 40 balloons of various sizes will be launched which are instrumented with ozonesondes to measure in detail vertical profiles of ozone and temperature, as well as aerosols and condensation nuclei, from the ground to about 29 kilometers above the surface. Antarctic ozone profiles: Palmer Station Arnold L. Torres, National Aeronautics and Space Administration, Wallops Flight Facility (S-293) Sudden and dramatic decreases in atmospheric ozone occur each austral spring over Antarctica. The most detailed picture of this depletion comes from relatively high-resolution vertical profiles obtained with balloonborne electrochemical ozonesondes. Continuing the project begun in 1987, scientists will take a large set of profiles over Palmer Station from September through November 1990, a period which should include the beginning of the ozone depletion as well as the peak. These profiles will provide clues to changes in the depth, vertical extent, ozone loss rates, and seasonal behavior of this phenomenon. The integrated profiles will provide correlative performance checks on remote-measurement systems. Climate Studies Chlorine-and bromine-containing trace gases in the Antarctic R.A. Rasmussen, Oregon Graduate Center (S-254) The project objective is to collect a year-long suite of air samples at Palmer Station. With these samples, scientists will investigate seasonal trends in trace-gas concentrations. The samples will be analyzed at the Oregon Graduate Center for a number of trace components, especially chlorine-and bromine-containing species. These trace constituents, which come from both natural and man-made sources, can alter the earth's climate and have been implicated in the chemical processes that contribute to the austral spring depletion of ozone over Antarctica. The study will contribute to a better understanding of the buildup of trace constituents, particularly those of high-latitude marine origin. Global monitoring for climatic change Eldon Ferguson (South Pole Station), Climate Monitoring and Diagnostics Laboratory, and James T. Peterson (Palmer Station), Environmental Research Laboratories, National Oceanic and Atmospheric Administration (S-257A and S-257C) The investigative team will continue long-term measurements of trace atmospheric constituents that may influence climate. Working at the South Pole Station observatory, four scientists during the austral summer and two personnel during the austral winter will measure carbon dioxide, surface ozone, winds, pressure, air and snow temperature, atmospheric moisture, and trace constituents from the station's clean-air facility. These data will be used to make time-series analyses of multi-year data records that focus on stratospheric ozone depletion, transantarctic aerosol transport and deposition, solar and terrestrial radiation fluxes on the polar plateau, the accumulation of and temporal variations in greenhouse gases, and the development of polar stratospheric clouds over
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United States Antarctic Research: Report No. 32 to the Scientific Committee on Antarctic Research (SCAR) 1 April 1989 - 31 March 1990 Antarctica. The objectives are to determine the rate at which concentrations of these atmospheric constituents change and to examine sources, sinks, and budgets. Working with climate modelers and diagnosticians, investigators will use these data to determine how the rate of change in aerosol concentrations affects climate. In support of this project, personnel at Palmer Station also will collect carbon dioxide samples. Lidar experiment at South Pole Giorgio Fiocco, Universita ''la Sapienza'', Rome, Italy (S-257B) The lidar is designed to take vertical profiles of the upper atmosphere. From these data, scientists are able to infer the molecular and aerosol concentration of air and, under some conditions, measure such parameters as atmospheric temperature. This information, which is useful in climate studies, is relevant to studies of atmospheric radiation, structure, and composition and may help us understand the mechanisms involved in ozone depletion. This is a cooperative project between the U.S. and Italian antarctic programs. Atmospheric halos and ice crystals Walter Tape, University of Alaska (S-264) The refraction and reflection of sunlight by ice crystals produce atmospheric halos. Different halos arise from different classes of crystal orientations and from different light-ray paths through the crystals. The unique atmospheric conditions of the antarctic interior frequently produce beautifully-formed simple, prismatic ice crystals that create strong, well-defined halo displays. Because these well-formed crystals typically occur near the surface, they can be collected easily for examination and comparison with the halos that they create. Extending the work performed at Amundsen-Scott South Pole Station, this austral summer investigators will photograph halos and simultaneously sample falling ice crystal at the Soviet station Vostok. By comparing computer simulations of halos with observed halos and crystals, they hope to clarify the relationship between crystal types and halo types. While sampling crystals, the investigators will measure the distribution and intensity of polarized light intensity from associated halos. Theoretically, the distinctive shapes formed by the distribution of polarized light should help define the size and orientation of the crystals. Data on crystal size and orientation obtained from the samples and from the halo simulations will enable verification and calibration of polarimetric techniques. Investigators will also conduct controlled experiments, such as seeding the atmosphere with dry ice, to produce simple, well-formed single-type crystals artificially. These artificially-produced crystals of known source, age, and growth conditions will help to clarify the special atmospheric conditions that produce the crystals for the elaborate halos in Antarctica. The research results have potential for remote sensing of atmospheric conditions. Climate studies at the South Pole Stephen G. Warren, University of Washington (S-265) Investigators will conduct an integrated study of the optical and physical properties of the antarctic snow surface. The four major objectives of the study concern the processes by which global climatic variability is imprinted into the antarctic ice record. Over the course of the austral summer, investigators will measure the effect of surface roughness (sastrugi orientation) on the angular distribution of reflected sunlight to provide information necessary for interpreting satellite remote-sensing data from the Earth Radiation Budget Experiment. These measurements will also be compared with the theoretical model of atmospheric radiation. By operating instruments during the austral
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United States Antarctic Research: Report No. 32 to the Scientific Committee on Antarctic Research (SCAR) 1 April 1989 - 31 March 1990 winter, investigators also will assist an ongoing experiment that involves measuring the spectral distribution of thermal infrared radiation from the atmosphere. To study the mechanism of dry deposition of atmospheric aerosols in the snow surface, they will measure the flow of air in and out of the permeable upper layers of firn and in samples of hoar frost; firn and hoar frost samples also will be examined for their isotopic composition. The measurements of airflow through the firn will enable investigators to evaluate the extent to which the concentration of aerosols in the firn and ice represent contemporaneous concentrations in the atmosphere. The hoar frost samples will provide data for a comparison of isotopic ratios to ambient air temperatures. Spectral bi-directional reflectance of antarctic snow and ice Robert W. Carlson, Jet Propulsion Laboratory, California Institute of Technology (S-266) Remote sensing of terrestrial and planetary polar areas is hindered by an incomplete understanding of the snow reflectance. The project objective is to contribute to a comprehensive understanding of the optical properties of antarctic snow and ice-information that can be extended to other regions. With this information, investigators hope to develop an experimental base, or "ground-truth," for remote sensing of glacial and snowpack regions. Such an experimental base will enable researchers to interpret more accurately aircraft and satellite observations to determine properties of snow surfaces, including such features as particle size and shape (properties that relate to the "age" of the snow surface), impurity content, and liquid-water content. Working near Amundsen-Scott South Pole Station, they will measure the spectral bi-directional reflectance of various snow and ice surfaces in the visible and near-infrared (0.4 to 5.0 microns), as well as the polarization effects. They will focus on how surface and subsurface grain properties influence spectral and angular variations of reflectance patterns. Antarctica provides several advantages for this type of investigation. First, the temperature of this continent, which is important to global climate, is determined largely by the optical properties of the snow and ice surface. Secondly, in contrast with temperate regions, the antarctic snow surface does not radically change during the day; consequently, lengthy measurements can be taken. Additionally, contamination from natural and manmade sources is greatly minimized in Antarctica. Operation of an aerosol sampling system at Palmer Station Gail dePlanque, Environmental Measurements Laboratory, Department of Energy (S-275) In March 1990, a team from the U.S. Department of Energy installed a surface-air sampling station at Palmer Station to measure manmade radionuclides, generate data messages, and transmit these data through National Oceanic and Atmospheric Administration satellites to Department of Energy receiving stations. The sampling station is part of a global array of automated stations, and its position in Antarctica fills a significant gap in this vital global data set. Boundary-layer dynamics over West Antarctica David H. Bromwich, Ohio State University (S-282) The antarctic surface wind field is highly irregular, is strongly affected by the surface slope, and has marked areas of convergence and divergence inland from the coastal margins. The interior provides large reservoirs of cold air that produce a persistent, gravity-driven (or katabatic) wind system. These convergent features appear to dominate the antarctic surface climate. This austral summer will be the first phase of this project. In October and November 1990, investigators will test atmospheric sensing equipment on
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United States Antarctic Research: Report No. 32 to the Scientific Committee on Antarctic Research (SCAR) 1 April 1989 - 31 March 1990 the Ross Ice Shelf near McMurdo Station at a site that has climate conditions similar to the Siple Coast. During the 1991-92 austral summer, this equipment will be moved to the Siple Coast, which offers a different dynamical setting from earlier experiments in the Terra Nova Bay region of East Antarctica. The overall objectives of the project are to describe and simulate both the downslope and cross-slope variations of the surface winds and temperatures in the Siple Coast confluence zone, to describe and model the impact of synoptic forcing along the terrain slope on the behavior of the surface winds, to investigate the interaction between the surface wind field and the potential temperature gradient along the snow surface, and to measure and simulate boundary layer wind and temperature profiles along terrain contours under the opposing factors of mass convergence and decreasing terrain slopes. Automatic weather stations: operation and research Charles R. Steams, University of Wisconsin (S-283) Although information taken from satellites on antarctic weather patterns is valuable, surface data are needed for confirmation. Automatic weather stations (AWS) measure surface pressure, air temperature, wind speed, and wind direction and transmit the data to satellites for interrogation by ground stations. The weather stations are used to study the barrier wind along the Transantarctic Mountains, vertical motion and sensible and latent heat flux from the Ross Ice Shelf, foehn winds flowing from the Beardmore and Byrd Glaciers onto the Ross Ice Shelf, katabatic flow in East Antarctica, and propagating weather systems at the South Pole. The weather stations also gather continuous and reliable meteorological data that support aircraft operations at McMurdo Station. During the 1990-91 field season, existing AWS units at South Pole Station, near McMurdo Station, and at sites accessible via the U.S. Coast Guard icebreaker Polar Sea will be checked, serviced, and relocated. Astronomy And Upper-Atmosphere Studies Support for operating an extra-low-frequency/very-low-frequency (ELF/VLF) radiometer at Arrival Heights, Antarctica Robert A. Helliwell, Stanford University (S-100) Controlled wave injection of low-frequency radio waves into the upper atmosphere from the ground enables scientists to study magnetosphere wave-particle interactions as well as observe and analyze the behavior of these waves and the response of ionized particles in the magnetosphere. With these techniques, scientists have acquired important quantitative information on the nature of wave-particle interactions in the magnetospheric plasma (low-energy, ionized gas that permeates the magnetosphere) under conditions that cannot be created in a laboratory. During the 1990-91 austral summer, observations will be made from the Arrival Heights upper-atmosphere facility near McMurdo Station. Information will be recorded about background magnetospheric wave activity in the extremely-low-frequency/very-low-frequency (ELF/VLF) range, as well as other effects produced by or associated with magnetospheric waves and particle precipitation. These experiments provide data that further our understanding of coherent radiation from magnetospheric plasma. These data are important to laboratory plasma physics and astrophysics. The results also can be applied to communications, remote sensing of magnetospheric plasma, and modification of the magnetosphere and the ionosphere by wave-induced particle precipitation.
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United States Antarctic Research: Report No. 32 to the Scientific Committee on Antarctic Research (SCAR) 1 April 1989 - 31 March 1990 High-latitude magnetic pulsation studies in the Antarctic and Arctic Roger L. Arnoldy, University of New Hampshire (S-102) This project will continue the collection and analysis of data from magnetic pulsation sensors located at high-geomagnetic-latitude stations in the Arctic (Sondre Stromfjord, Greenland) and Antarctic (McMurdo and South Pole stations). The pulsations measured, which range in frequency from a few millihertz to a few hertz, are used in conjunction with similar data acquired from a number of satellites and are vital to scientists' understanding of the mechanism by which energy is transferred from the solar wind to the earth's magnetosphere. Measurement of vertical atmospheric electric current at a network of sites in Antarctica including manned stations and automatic geophysical observation Edgar A. Bering III, University of Houston (S-103) During this field season, a network of eight atmospheric current sensors will be deployed in Antarctica-two at manned stations and six at automatic geophysical observatories. The scientific objectives of this project fall into two broad areas: atmospheric electricity and ionospheric electrodynamics. For a study of atmospheric electricity, the network will provide a measure of the power and voltage level in the global circuit and a preliminary estimate of the "geoelectric index." With the ionospheric electrodynamics data, scientists will be able to interpret the differences in the air-earth current at various sites in terms of differences in the electrostatic potential of the ionosphere above the sites. If most stations in the network are installed and operating, more or less continuous "snapshots" of the ionospheric electrostatic potential, and, therefore, convection patterns in the polar cap, should be obtained. Studies of the relationship of statistical patterns to instantaneous patterns, substorm responses, and hemispheric differences are anticipated. Auroral imaging Stephen B. Mende, Lockheed Palo Alto Research Laboratory (S-104) Installed in 1982 at South Pole Station, an image-intensified all-sky camera has enabled scientists to monitor cusp auroral activity. This camera produces images of weak optical emissions at the latitude of the cusp, an important but poorly understood boundary region of the earth's magnetosphere. For data analysis, data have been used from a two-channel photometer at Siple Station, from other projects at South Pole and Siple stations for correlation, and from the auroral imagery on the Dynamics Explorer satellite (DE-1). The primary interest is in the extent to which aurora seen by DE-1 in the Northern Hemisphere mirror those observed at the South Pole. During this austral summer, a research team will inspect and service this equipment. The system will be operated and maintained by South Pole personnel during the austral winter. Very-low-frequency sensing of thunderstorms and radiation-belt coupling Umran S. Inan, Stanford University (S-106) Recent research results suggest that lightning and thunderstorms may have a major role in the precipitation of trapped particles from the radiation belts surrounding Earth. By using ground-and satellite-based observations researchers have established that detectable lightning-induced electron precipitation and associated ionospheric perturbations do occur. Such precipitation is evidence of a fundamental coupling mechanism between the magnetosphere-ionosphere system and the middle atmosphere. The project focuses on the bursts of precipitation that lightning discharges induce at middle to low latitudes. The results help to determine the role of lightning and
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United States Antarctic Research: Report No. 32 to the Scientific Committee on Antarctic Research (SCAR) 1 April 1989 - 31 March 1990 thunderstorms in relation to magnetospheric electrons and the way in which the atmosphere, ionosphere, and magnetosphere are coupled. To study this phenomenon, scientists will use the ionospheric density enhancements that it produces. These enhancements are detected as amplitude and phase perturbations on very-low-frequency, low-frequency, and middle-frequency radio signals that propagate along geomagnetic field lines. From recent research, scientists know that such measurements are a powerful and possibly unique ground-based tool for detecting particle precipitation at mid-and low-latitudes. While working at Palmer Station, technicians will conduct simultaneous, high-resolution measurements of the amplitude and phase of subionospheric very-low-frequency, low-frequency, and middle-frequency signals to determine the spatial distribution, temporal signatures, and magnetic conjugacy of lightning-induced precipitation. High-resolution helioseismology from the South Pole Martin A. Pomerantz, Bartol Research Institute, University of Delaware (S-109B) During the 1981-82 austral summer, a solar observatory about 4 miles (6.5 kilometers) from South Pole Station was utilized. With this telescope and a modified version used during the 1982-83 and 1984-85 austral summers, global solar oscillations have been observed and recorded. These observations have helped to extend our understanding of the structure and dynamics of the solar interior. During the 1981-82 austral summer, simultaneous, high-resolution photographs were obtained at two different wavelengths over protracted periods. During austral summer 1990-91, using an enhanced camera, new photographs will be taken for comparison with the earlier ones. With these data, possible changes in the level of solar activity will be investigated, as well as exploration for new solar features. Observations of ultra-high-energy, gamma-ray sources from the South Pole Martin A. Pomerantz, Bartol Research Institute, University of Delaware (S-109D) Since early in this century when cosmic rays were discovered, scientists have sought to determine their point of origin. Initially, they believed that cosmic rays were energetic electromagnetic radiation. More recent data have shown that cosmic rays are electrically charged particles, mainly hydrogen nuclei and more particularly protons. The circumpolarity of the sky over South Pole Station makes this site one of the few from which continuous observations can be made for 200-teraelectronvolt gamma-rays from a large number of X-ray binaries and related compact objects-potential emitters of primary cosmic rays. Because of the station's location, scientists will be able to search for regularities of what are, in the few cases confirmed to date, somewhat episodic sources. The continuous exposure, coupled with the favorably high altitude, will also enable the discovery of weaker sources in the southern sky where there is a preponderance of potential ultra-high-energy, gamma-ray sources. To obtain directional data, an array of detectors that respond to extensive air showers produced by ultra-high-energy, gamma-rays incident on the earth's atmosphere will be used. Antarctic neutral thermospheric and mesospheric dynamics and thermodynamics Gonzalo J. Hernandez, University of Washington (S-110) The dynamics and thermodynamics of the antarctic mesosphere and thermosphere-those regions above the stratosphere beginning at 50 kilometers altitude and extending to the outer edge of the atmosphere-will be studied through the use of a high-resolution, high-luminosity spectrometer near Amundsen-Scott South Pole Station. The station's location in relation to the south magnetic pole makes it possible to study the southern
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United States Antarctic Research: Report No. 32 to the Scientific Committee on Antarctic Research (SCAR) 1 April 1989 - 31 March 1990 hemisphere cusp during three months in the winter season. Because of the greater degree of symmetry between the geographic and geomagnetic poles in the southern hemisphere, solar ultraviolet radiation and solar-wind particle effects interact and influence the dynamics and temperature in the upper atmosphere differently than they do in the northern hemisphere. Data from this investigation will help to determine the extent of this interplay during the solar activity minimum. Other studies include the determination of the ion-neutral coupling in the upper thermosphere and its variation. The data from the optical station in Antarctica, integrated with data from other southern hemisphere locations, will give a picture of southern hemisphere thermospheric circulation not previously possible. Direct measurements of ion drifts will provide a measure of the ion-neutral coupling in the thermosphere near the station. Finally, optical measurements of the antarctic mesosphere will continue to be made to study the dynamics and thermodynamics of this very important atmospheric region. Polar experiment network for geophysical upper-atmosphere investigations (PENGUIN) Ted J. Rosenberg, University of Maryland (S-111) A comprehensive investigation of the polar ionosphere at high geomagnetic latitudes in Antarctica will be carried out by using automatic geophysical observatories and selected manned stations. These arrays of instruments will be used to study the energetics and dynamics of the high-latitude magnetosphere on both large and small scales. One of the objectives is to develop a polar-cap magnetic index to provide the first continuous characterization of polar-cap variability. The research will be carried out coincident with in situ observations of the geospace environment by spacecraft, in close cooperation with other nations working in Antarctica, and in conjunction with conjugate studies performed in the northern hemisphere. Cosmic background isotrophy measurements from the South Pole Mark Dragovan, Princeton University (S-113) The cosmic microwave background comprises thermal radiation that fills the universe. It originated about 100,000 years after the Big Bang when electrons and protons recombined into hydrogen, thereby causing the gas to become transparent to thermal radiation. Any density inhomogeneity in the universe at that time should have left an imprint on the background radiation. Detecting this imprint has so far been unsuccessful, because more sensitive equipment and longer integration times were required. The measurements taken for this project, however, will be made at wavelengths both longer and shorter than the peak in the cosmic background radiation spectrum in hopes of detecting even slight variations, which theory tells us should be present but which measurements, thus far, have failed to detect. Because these radio waves are strongly absorbed by the atmosphere, especially water vapor, South Pole Station, which is the second driest inhabited place on Earth, is the best place to make these measurements. Another great advantage of this location is that the circumpolar motion of the sky makes it possible to observe any spot in the sky through a constant thickness of atmosphere for any length of time. South Pole studies of the cosmic background radiation Philip M. Lubin, University of California at Santa Barbara (S-115) Measuring fluctuations (or anistropy) in cosmic background radiation is one of the few experimental inputs available to atmospheric physicists for comparison with cosmological models. Because large-scale (greater than 10°) measurements of these variations can be disrupted by emissions from our galaxy, particularly by high-galactic latitude dust
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United States Antarctic Research: Report No. 32 to the Scientific Committee on Antarctic Research (SCAR) 1 April 1989 - 31 March 1990 emissions, the objective is to make observations at the 3-millimeter-wavelength level, where galactic emission is near its minimum. Atmospheric fluctuations, particularly water vapor, generally create problems for ground-based anistropy measurements, but results from earlier antarctic studies indicate that the extreme cold and low water-vapor content of the atmosphere at South Pole provide an excellent environment for this type of measurement. During the 1990-91 austral summer, investigators will again collaborate with Princeton University researchers (S-113) in their study of cosmic background radiation by using a liquid-helium-cooled detector that operates at a 3-millimeter wavelength. A 1-meter telescope, developed as a part of the balloonborne program, will allow them to make measurements on the order of 1°. Measurements will be made in an angular region that has not been well investigated, that is complementary to other experiments, and where the predicted fluctuations are expected to be near maximum. These measurements will also help scientists to understand better the atmospheric fluctuations, useful information for future millimeter and submillimeter wave astronomical investigations. Cosmic and solar hard X-ray and gamma-ray spectroscopy from Antarctica Robert P. Lin, University of California at Berkeley (S-116) Astrophysicists believe that supernova explosions produce most of the heavy elements in the universe through the processes that occur as a star's core collapses and explodes during supernova. Observing and recording the spectral properties of gamma-rays appear to be the best ways to study this process because many of the heavy elements are first produced as unstable nuclei that emit gamma rays of characteristic energies as they decay. On 23 February 1987, astronomers and astrophysicists observed Supernova 1987A in the Large Magellanic Cloud, a companion galaxy to the Milky Way. This was the closest supernova to Earth in more than 300 years and offers astronomers and astrophysicists a unique opportunity to study in detail a supernova explosion, to learn more about the process of explosive nucleosynthesis, and to search for cosmic gamma-ray bursts and astronomical events that occur during supernovas. To accomplish this, investigators will participate in a multi-institute project to launch a 28.4-million-cubic-foot high-altitude helium balloon equipped with detectors. It is anticipated that the balloon will reach an altitude of between 120,000 and 130,000 feet and that it will stay aloft for 20 days. Measurement of cosmic-ray composition and spectra using emulsion chambers-Japanese-American Cooperative Emulsion Experiment Thomas A. Parnell, National Aeronautics and Space Administration, George C. Marshall Space Flight Center, and R.J. Wilkes, University of Washington (S-119) Since 1979 there have been collaborations with Japanese investigators in a series of experiments to study the composition, spectra, and interactions of cosmic-ray nuclei. Although initially NASA personnel worked to develop an electronic counter and performed calculations to support data analysis, the focus during the last seven years has been to perform passive detector analysis, specifically using x-ray film densitometry and emulsion chambers. As participants in the antarctic long-duration balloon project, NASA investigators use similar passive techniques to trace and measure cosmic-ray events and perform calculations for data analysis. Over the last three years, the group has analyzed data from six balloonborne experiments and has produced unique data on nucleus-to-nucleus interactions at high energies (greater than 1,000 gigaelectron volts).
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United States Antarctic Research: Report No. 32 to the Scientific Committee on Antarctic Research (SCAR) 1 April 1989 - 31 March 1990 Solar and heliosphere studies with antarctic cosmic-ray observations John W. Bieber, Bartol Research Institute, University of Delaware (S-120) Cosmic rays provide a powerful tool for studying exotic astrophysical processes that occur on the Sun and in its far-reaching atmosphere that controls space near Earth. Antarctic monitoring stations are crucial for probing interplanetary plasma dynamics through observations of variations in relativistic (over 1 gigaelectronvolt) galactic cosmic rays. At McMurdo and South Pole stations, investigators will continue year-round observations of cosmic radiation and collaborate with the magnetospheric cusp program. To enhance understanding of the solar physical processes that control the electromagnetic conditions in the earth's environment, these data are used in conjunction with data from other ground-based instruments and spacecraft. The objectives are to explore the nature of long-term variations and North-South asymmetries of solar activity; to investigate the acceleration, coronal transport, and interplanetary transport of energetic solar particles; to learn more about the three-dimensional structure of interplanetary magnetic turbulence; and to improve understanding of the solar modulation of galactic cosmic rays. All-sky camera measurements of the aurora australis from Amundsen-Scott South Pole Station Frank T. Berkey, Utah State University (S-122) Amundsen-Scott South Pole Station, located at the south geographic pole, is a unique platform from which to undertake measurements of the polar ionosphere. Because of the configuration of the geomagnetic field in the Southern Hemisphere, the station is situated in such a way that dayside auroras can be viewed for several hours each day. Research has shown that the precipitation of low-energy particles, which enter the magnetosphere by means of the solar wind, cause these auroras. The objective is to continue making winter observations of the aurora by operating a 35-millimeter all-sky camera system that has been used since 1967. The data that are acquired will be used to investigate dayside auroral structure, nightside substorm effects, and polar-cap arcs. These studies can also be used to obtain further insight into the physics of the magnetosphere, the convection of plasma in the polar cap, and winds in the thermosphere. Measurements of iron-group isotopic composition in cosmic rays with a lightweight, balloonborne spectrometer launched from Antarctica P. Buford Price, University of California at Berkeley (S-124) An extraordinary amount of astrophysical information can be extracted by determining the amount of isotopes of iron, nickel, and neighboring elements in cosmic rays. Unfortunately, inadequate statistics and poor mass resolution have limited past efforts to study these isotopes. The objective is to measure isotopic composition of iron, manganese, cobalt, and nickel in galactic cosmic radiation using balloonborne instruments launched near McMurdo Station as part of the Long-Duration Ballooning Program. These measurements will provide information about cosmic-ray origin and acceleration, the structure of interstellar medium, and stellar evolution. The balloons will carry a special glass to an altitude between 120,000 (36,580 meters) and 130,000 feet (39,624 meters), where the glass will be exposed for as long as 20 days. After the glass is recovered, investigators will etch it with a strong acid. This process reveals the tracks left by energetic cosmic rays that penetrate the glass. By studying the etched tracks, investigators can accurately determine the mass, charge, and energy of the isotope that caused them.
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United States Antarctic Research: Report No. 32 to the Scientific Committee on Antarctic Research (SCAR) 1 April 1989 - 31 March 1990 Observation of very-high-energy gamma-ray sources from the South Pole Robert M. Morse, University of Wisconsin, and James A. Gaidos, Purdue University (S-125 and S-126) Although cosmic radiation was discovered more than 75 years ago, its origin remains a mystery. Gamma rays represent only a small fraction of the total cosmic-ray flux, but they propagate undeflected from their sources to Earth, while the dominant, electrically charged component is deflected by magnetic fields. The objective is to identify sources of cosmic radiation which, according to some theories, may have been created by a modest number of supernova. To do this, an atmospheric Cherenkov telescope will be installed near the South Pole. The telescope consists of an array of parabolic mirrors with photomultiplier tubes at their foci that can detect light from very-high-energy (VHE) interactions in a small amount of atmosphere. The geographic South Pole is an ideal site for this research because it is possible to view a single object for extended periods through a constant thickness of atmosphere. At a mid-latitude site, observations are limited to a few hours of viewing at a time. Sodium-lidar studies of the antarctic upper atmosphere at Amundsen-Scott South Pole Station Chester S. Gardner, University of Illinois (S-127) The antarctic upper atmosphere is a region of diverse, complex interactions where chemistry and dynamics are greatly influenced by the tropospheric and thermospheric vortices. This region is attracting considerable attention because of the springtime depletion of ozone above Antarctica. Although the lower atmosphere has been explored for many years using various balloonborne, rocketborne, and ground-based instruments, the relative isolation of Antarctica and the paucity of suitable instruments has inhibited the study of the antarctic mesosphere (50 to 80 kilometers) and lower thermosphere (above 80 kilometers). A sodium lidar is a powerful tool for exploring upper atmosphere structure and dynamics, including stratospheric aerosols, mesospheric temperatures, gravity waves, tides, and vertical transport near the mesopause, the boundary between the mesosphere and thermosphere where there is a temperature minimum. The lidar can detect the sodium layer at about 56 miles (90 kilometers) altitude and, by measuring the height and density of this layer, determine the vertical motion of the upper atmosphere. The objective is to install and operate a sodium lidar at Amundsen-Scott South Pole Station so that information relevant to ozone depletion can be obtained, particularly data concerning the dynamics of upper atmospheric regions. Low-frequency/high-frequency programmable frequency receiver to the antarctic automatic geophysical observatories James W. LaBelle, Dartmouth College (S-128) For decades, intermittent ground observations have given tantalizing hints that the Earth's high-latitude ionosphere emits radio waves in the low-frequency to high-frequency band (0.15-9.6 megahertz). Rocket and satellite observations in the upper regions of the ionosphere and magnetosphere commonly indicate the existence of such terrestrial radio signals, particularly in the lower portion of this frequency range. Theoretical studies have indicated that some of these emissions should be able to penetrate the ionosphere and be detected at ground level, but there is a need for a ground-based recording effort to study this much-neglected radio band to confirm these theories and provide insight into auroral emission and wave-propagation processes. The unmanned automatic geophysical observatories (AGOs) are ideal for this effort because the sensitivity at these frequencies is greatly affected by human-produced transmissions,
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United States Antarctic Research: Report No. 32 to the Scientific Committee on Antarctic Research (SCAR) 1 April 1989 - 31 March 1990 Center of Ohio State University, the U.S. Geological Survey will conduct a combined airborne radar and aeromagnetic survey of these two regions to gather specific information about their nature and origin as well as the relationship between Cenozoic volcanism and the tectonic and glacial history in the regions. The grid spacing will be 5 kilometers and navigation will be by radio-positioning. In addition to constructing maps of subglacial topography and magnetic intensity, investigators will also try to reconstruct the position of subglacial diffractors in three dimensions. This reconstruction, especially when combined with the magnetic results, should give new information about the distribution of escarpments and, therefore, the tectonic relationships within the region. Diversity and distribution of fossil floras from southern Victoria Land Edith L. Taylor and Thomas N. Taylor, Ohio State University (S-068) The research objectives of this project are to make detailed and systematic collections of fossil floras ranging from Devonian to Jurassic (between 405 million to 135 million years old) from the ice-free valleys of southern Victoria Land. Once the fossils collected from these areas are returned to the laboratory, the sites (logged at the time of collection) will be assessed for the quality of preservation, diversity and types of plants present, and the potential for further collecting. Throughout the fieldwork, some reconnaissance for additional fossil plant localities will also be undertaken. Geological and geophysical studies in the Ford Range of Marie Byrd Land, West Antarctica Bruce P. Luyendyk and David L. Kimbrough, University of California at Santa Barbara (S-070) In Gondwanaland reconstructions, Marie Byrd Land is juxtaposed with portions of New Zealand and the Campbell Plateau. The breakup of the Pacific margin of Gondwanaland is reflected in well-documented Cretaceous and Early Tertiary extension and rifting in the region. A sequence of magnetic anomalies records the opening of the Tasman Sea and the splitting off of New Zealand about 85 million years ago. Events in Marie Byrd Land may relate to the tectonics of the Gondwanaland Pacific margin before and following this rifting. Although there are many geologic parallels between New Zealand and Marie Byrd Land, it is unclear whether these similarities indicate that the two regions were part of the same unit. From previous research in New Zealand's Western Province, scientists know that a sequence of Cretaceous metamorphic events that are related to the rifting of Gondwanaland exist. Through paleomagnetic studies, they also have identified a Permian terrane that formed during the Early Jurassic just before Gondwanaland broke up. By studying the tectonic history of the Ford Range in Marie Byrd Land, the investigators hope to determine whether or not similar events occurred in this part of Antarctica. Other geologists have described West Antarctica as a collage of microplates that appear to have been closely related to each other and Antarctica since the Jurassic, but the relationship of Marie Byrd Land to these microplates during this time is less clear. Paleomagnetic data for the region do indicate that Marie Byrd Land was at a higher latitude about 100 million years ago and that since this time it has rotated independently of East and West Antarctica. The project objective is to sample and study exposed Late Precambrian and Early Paleozoic metasediments, gneisses, and migmatites, carboniferous and Cretaceous plutonic rocks, and Cenozoic and Quaternary volcanic rocks. Data from petrologic, geochronologic, and paleomagnetic studies also will be used to reconstruct the tectonic evolution of Marie Byrd Land.
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United States Antarctic Research: Report No. 32 to the Scientific Committee on Antarctic Research (SCAR) 1 April 1989 - 31 March 1990 Geochemistry and petrology of the lower crust, Antarctica: evaluation over space and time Jonathan H. Berg and Ruth I. Kalamarides, Northern Illinois University (S-071) During previous field seasons, the research team has investigated the nature of the upper and lower crust in southern Victoria Land as recorded in alkaline magmas of the Erebus Volcanic Province over the last few million years. This austral summer, they want to expand their knowledge of the antarctic crust by sampling contemporaneous alkaline magmas of the Hallett Volcanic Province that extend about 600 kilometers to northern Victoria Land. Recently, they discovered that 450- to 500-million-year-old dikes, such as those found in southern Victoria Land, have inclusions of igneous rock from the lower crust and possibly the mantle. Consequently, the investigators have the opportunity to study two suites of samples of the earth's crust and mantle brought to the surface in the same location but separated by about 500 million years. By also extending the southern Victoria Land studies, they will be able to see how the upper mantle and lower crust have changed over the last 500 million years. Samples from northern and southern Victoria Land will help to understand better the geologic and tectonic history of the Transantarctic Mountains, as well as the tectonic history of Gondwanaland. Fundamental knowledge of the earth's upper mantle and lower-crust composition and evolution will be increased. Because less. is known about the lower crust than the portions above and below it, these data will enhance understanding of the earth's evolution and contribute information critical to completing cross-sections in the Global Transect Program and to geophysical studies of the Ross Sea. Mesozoic and Cenozoic kinematic evolution of the Transantarctic Mountains Terry J. Wilson, Ohio State University (S-072)The study objective is to examine the crustal structures produced during two phases of uplift of the Transantarctic Mountains. Along the front of the mountains near the Ross Sea are structures from the more recent of these two uplift phases. Near the Beardmore Glacier, rock formations associated with older periods of magmatic intrusion and fracturing are best developed in and around the Marshall Mountains. Rock formations produced during the more recent phase of uplift are found in the Dominion Range and along the front of the mountains adjacent to the Ross Ice Shelf. This austral summer the field party will concentrate on measuring and mapping the orientation of faults, fractures, and igneous dike swarms (large groups of linear, parallel, or radially oriented igneous rocks that cut across or through other rocks) near the Beardmore Glacier. These observations and measurements will be compared to those that were made during the 1989-1990 austral summer in southern Victorian Land. As a result of last year's field studies, the investigators have already identified critical areas for establishing the regional significance of fault and fracture patterns. Cosmic-ray exposure-age dating applied to antarctic glacial geology Mark D. Kurz, Woods Hole Oceanographic Institution (S-077) Dating surface rocks by exposure-age dating techniques has great potential for glacial geology. Although scientists have used extensively the accumulation of elements produced in situ to date meteorites, they have only recently begun to use this technique to date terrestrial rocks. Isotopes of helium in surface rocks are produced by cosmic-ray-induced, high-energy nuclear reactions that release large numbers of protons or neutrons. Recent studies of radiocarbon-dated lava flows have shown that measurements of helium produced this way can be used to determine exposure ages. The study goal is to use this technique, for the first time, to date glacial deposits in the ice-free areas of
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United States Antarctic Research: Report No. 32 to the Scientific Committee on Antarctic Research (SCAR) 1 April 1989 - 31 March 1990 southern Victoria Land, which provide an ideal testing site for this method because of uniquely exposed, well-dated glacial moraines. Investigators hope not only to resolve some questions about the helium exposure-age method but also to define better the history of the antarctic ice sheet and its relationship with global climate. Initially, they will focus on collecting samples and measuring quartz from sandstone boulders in dated moraines of Arena Valley. Extensive sampling by the field team will enable them not only to gain sufficient data to help elucidate the history of the ice sheet but also to understand better the distribution and retention of helium with quartz. Because quartz is common worldwide, the study results also should interest glacial geologists not working in Antarctica. Degassing and crystallization of anorthoclase phonolite magma, Mount Erebus Phillip R. Kyle, New Mexico Institute of Mining and Technology (S-081A) Mount Erebus contains a persistent convecting lava lake of magma that is composed predominantly of alkali feldspar. The lake is the top of a magma chamber and functions as a window through which the processes operating within a magma chamber can be observed. Because of the magma's mineral composition, the activity and convection complement studies at other volcanoes such as Kilauea and Mount St. Helens. Observations of sulfur-dioxide emissions are providing new insights into sulfur solubility in this type of magma and how degassing occurs. Beautiful, large crystals of feldspar (or anorthoclase phenocrysts), often over 88 millimeters long, are well developed in older lavas and in the active lava lake. To date, no studies have addressed the nucleation and growth of such large crystals. The objectives of this study are to continue surveillance of the volcanic activity of Mount Erebus, to monitor the latest eruptive cycle, and to estimate the growth of the anorthoclase phenocrysts. Investigators will also address several fundamental questions regarding sulfur-dioxide degassing and the contribution of Mount Erebus to the nearly pristine antarctic atmosphere. By sampling the plume from the crater rim, they will be able to collect samples of volatile acid gases and trace metals. West antarctic volcano exploration (WAVE) Phillip R. Kyle, New Mexico Institute of Mining and Technology (S-081B) Marie Byrd Land, one of the world's largest alkali volcanic provinces, contains a unique record of the Late Cenozoic glacial and volcanic history of Antarctica; however, investigations of this region have been limited to reconnaissance studies and recent studies of Mount Takahe and Mount Murphy. From this limited data set, investigators know that the earlier reconnaissance interpretations of the subglacial origins of these volcanoes are incorrect. The study objective is to examine the glacial and volcanic history of the region and the origin of the volcanoes. Working as part of a U.S., British, and New Zealand investigation, these scientists will study the geochemistry, volcanology, and tectonic history of these Marie Byrd Land volcanoes. During the 1990-91 austral summer, the team will focus on volcanoes near the Toney Mountain and Mount Hampton. Geochemical, tectonic, and glaciovolcanic investigations will be made using geochemical and isotopic analyses, argon-40/argon-39 dating, scanning electron micrograph studies, and paleo-and rock-magnetic analysis. Study of sediment, glacier ice, and silicate spherules, Walcott Névé, Antarctica Gunter Faure, Ohio State University (S-089) Subglacial bedrock ridges disrupt the flow of the east antarctic ice sheet and make the margin a very sensitive area. The resulting ice fields expose a stratigraphic section of
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United States Antarctic Research: Report No. 32 to the Scientific Committee on Antarctic Research (SCAR) 1 April 1989 - 31 March 1990 the ice sheet that includes very old basal ice, which ablates to form supraglacial moraines. The study objectives include mapping the surface elevation and thickness of ice entering the Walcott Névé and Law Glacier from the Beardmore Glacier area to document what effect bedrock topography has on local ice-flow patterns; identifying by oxygen-isotope composition the Pleistocene-Holocene boundary in exposed ice; studying selected fragments from supraglacial moraines to learn about the geology of the ice-drainage basin on the east antarctic craton; and studying the geochemistry, mineralogy, and isotopic composition of silicate spherules that are found abundantly in the area's glacial sediments. Investigators also will integrate geologic and glaciologic information to explain the occurrence of meteorites and silicate spherules along the east antarctic ice sheet margin and elsewhere in Antarctica. Determining exposure ages and erosion rates of bedrock surfaces in Antarctica Roy Middleton and Robert Giegengack, University of Pennsylvania (S-092) Determination by accelerator mass spectrometry of concentrations of the cosmogenic radionuclides beryllium-10 and aluminum-26, produced by cosmic rays in quartz on exposed bedrock surfaces through high-energy nuclear reactions, has been demonstrated to provide valuable data on exposure times and rates of erosion for those surfaces. The oldest exposure times found using this method are those measured in bedrock samples from Antarctica. During the course of this study, investigators will measure concentrations of beryllium-10 and aluminum-26 in bedrock samples from previous expeditions, as well as from their own collections, and interpret those measurements in terms of exposure ages, erosion rates, and Quaternary glacial history. Stratigraphy, paleontology, structural geology, and paleoglaciology of the late Neogene Sirius Group of the Dominion Range/Beardmore Glacier region of the Transantarctic Mountains Peter N. Webb, Ohio State University (S-093) Previous studies have convinced investigators that the Dominion Range/Beardmore Glacier area has a highly significant Late Neogene climate record of Antarctica. In this study, field and laboratory work will focus on determining pre-Sirius paleotopography and structural geology; taking measurements and recording observations; collecting macro-and microplant material; searching for fossil insect, crustacean, bivalve, and fish material; collecting additional samples from the Sirius Group with the aim of expanding the collection of Cretaceous/Paleogene/Neogene microfossils which were transported from the interior basins of East Antarctica during the Late Pliocene/Early Pleistocene; and continuing to test the hypothesis that Pliocene glaciation in this part of Antarctica involved high-frequency variations of relatively small ice sheets, the development of protracted warm periods, and major marine invasions of the antarctic interior associated with periodic higher sea levels. Geochemistry of Paleozoic granites of the Transantarctic Mountains: phase 2 Donald J. DePaolo, University of California at Berkeley (S-094) One of the most important advances in plate tectonics is the realization that the mantle of the Earth behaves like a fluid. It transports, by convection, the internal heat of the Earth to the surface. This convection drives both plate tectonics and magmatism. Since the mantle represents about two-thirds of earth's mass, understanding the fluid-like nature of the mantle is tantamount to understanding the evolution of the planet. This project, a systematic study of the portion of Early Paleozoic granitic rocks of the central Transantarctic Mountains that may have been formed from magma, seeks to increase the
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United States Antarctic Research: Report No. 32 to the Scientific Committee on Antarctic Research (SCAR) 1 April 1989 - 31 March 1990 body of knowledge about the mantle by focusing on three objectives: understanding the origin and structure of the granitic rocks; investigating the age and origin of the Precambrian basement rocks; and constructing tectonic-magmatic models of the Early Paleozoic evolution of the antarctic continental margin. Quaternary climate record from the Antarctic Peninsula regions, Antarctica David H. Elliot and Scott E. Ishman, Ohio State University (S-208) Preliminary analyses of benthic foraminiferal distribution, sediment distribution, and water-column profiles from the Bellingshausen/Pacific sector of the Antarctic Peninsula have suggested that the observed patterns are influenced by oceanographic, glacial, and climatic conditions. This study will supplement these preliminary findings and will provide new information on the microhabitat and geochemical associations between the surface sediments and benthic foraminifera. Investigators will analyze modern sediment flux and distribution, water-column profiles, and benthic foraminiferal distribution. The faunal and environmental associations observed in the modern setting will then be used to formulate an interactive model which can be Used, in turn, to infer paleoceanographic and paleoclimatic conditions in downcore sediments, thus helping to reevaluate the Cenozoic marine records from samples previously collected in the antarctic margin region. SOLID EARTH GEOPHYSICS Paleomagnetic studies designed to test the Mesozoic paleoposition of the Antarctic Peninsula and test models of the Weddell Sea opening Ann M. Grunow, Ohio State University and Ian W.D. Dalziel, University of Texas at Austin (S-063A) Investigators will continue examining the geologic history of West Antarctica and the relationship of West to East Antarctica by collecting paleomagnetic samples from Mesozoic-age rocks on the Antarctic Peninsula. Resolving the position of the different West Antarctic crustal blocks is critical for understanding when and how the Weddell Sea opened and for understanding the resulting paleoclimatic, paleoceanographic, and paleobiological implications. By systematically collecting paleomagnetic samples ranging in age from the Triassic through Late Cretaceous, they hope that a more complete apparent polar wander path can be constructed for the Antarctic Peninsula. Such a polar wander path can help constrain the position of the Antarctic Peninsula with respect to East Antarctica and provide information on the time of opening of the Weddell Sea. Dry valley seismograph project Nicholas A. Orsini, U.S. Geological Survey, Albuquerque Seismological Laboratory (S-078) Increasing the availability of high-quality seismic data from Antarctica is a long-term objective of many investigators. Such data, when combined with data from the Worldwide Standardized Seismological Network, would provide needed azimuthal control for locating seismic events in both the Northern and Southern Hemispheres. During several austral summers, investigators surveyed sites and installed equipment in southern Victoria Land's ice-free valleys. Eventually, data will be transmitted in real time via a geosynchronous satellite to the U.S. Geological Survey's Albuquerque Seismological Laboratory as part of a larger seismic data collection network. During the 1990-91 austral summer, investigators will perform maintenance on telemetry-radio equipment
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United States Antarctic Research: Report No. 32 to the Scientific Committee on Antarctic Research (SCAR) 1 April 1989 - 31 March 1990 and clean and check the operation of the Wright Valley station. Support for the global seismic station at Amundsen-Scott South Pole Station Rhett Butler, Incorporated Research Institutions for Seismology (IRIS) (S-090) Amundsen-Scott South Pole Station is uniquely located for long-term global seismic studies. The station is a seismically quiet platform, which lies on the earth's rotational axis and can be used as a site to measure long-period oscillations of the Earth. Its location on the Great Circle Paths coincides with portions of the Mid-Atlantic Ridge and the East Pacific Rise and includes active seismic regions and other features of intense geophysical interest. IRIS, a non-profit consortium of 57 U.S. universities, creates and manages research facilities for seismology. Currently, IRIS is funding the University of California at Los Angeles to operate the South Pole seismic facility. GLACIOLOGY Polar Ice Coring Office drilling projects John J. Kelley, University of Alaska (S-150) Ice cores provide valuable information on past atmospheric constituents and climate. During the 1990-91 austral summer, the Polar Ice Coring Office will support U.S. and New Zealand investigators (S-159 and S-165) who will be conducting a seismic investigation along the boundary of East Antarctica and the Ross embayment and near the Beardmore Glacier. Antarctic ice-sheet response to global Pliocene warming George H. Denton, University of Maine (S-156) Glacial geologic evidence, including high-elevation trimlines, striated bedrock, and basal tills, from strategic positions in the Transantarctic and Ellsworth Mountains, implies that massive overridings by a temperate ice sheet occurred more than two million years ago in the Late Tertiary. From other data, scientists infer numerous fluctuations with maximum ice volumes in East Antarctica greater than those existing during the last two million years. Evidence from the ice-free valleys of southern Victoria Land and near the Beardmore Glacier also indicate that a younger massive overriding by a polar ice sheet occurred in the later Tertiary. Glacial geologic and soil studies of lateral moraines suggest a less massive, later Quaternary (two million years ago) expansion that featured peripheral thickening and interior thinning in comparison to the present. The study objectives are to develop a glacial chronology, stratigraphy, and description of tectonic uplift through critical time intervals represented by these glaciations. To do this, investigators will acquire data for argon-40/argon-39 isotopic dating of McMurdo volcanic eruptive centers that simultaneously date overriding and monitor tectonic uplift, stratigraphy of dated volcanics and silty overriding tills through a wide range of elevations, radiocarbon dates of late Wisconsin moraines in eastern Taylor Valley, and uranium-series dates of moraines in Taylor Valley. This austral summer, investigators will continue sampling of volcanic deposits and interbedded glacial tills in Taylor Valley and in the nearby Asgard and Quartermain Ranges. The results of this research will improve antarctic glacial chronology and associated tectonic history of the Transantarctic Mountains and will allow numerical ice-sheet reconstructions that help scientists to develop atmospheric modeling experiments of the influence of these ice sheets on southern hemisphere climate.
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United States Antarctic Research: Report No. 32 to the Scientific Committee on Antarctic Research (SCAR) 1 April 1989 - 31 March 1990 Seismic investigation of the plate boundary between east and west antarctica Uri ten Brink; Stanford University (S-159) The Seismic Experiment-Ross Ice Shelf (SERIS) program will examine the plate boundary between East Antarctica and the Ross embayment. Investigators will first acquire a 150-kilometer-long multichannel seismic reflection line starting on the Ross Ice Shelf and entering the Transantarctic Mountains front through one of the outlet glaciers. A reversed-refraction profile and several wide-angle reflection profiles will be collected along this multichannel seismic line. Interpretation of the data, flexural modeling of the uplift and the subsidence, analysis of the seismic stratigraphy and modeling of the gravity will then be done. This cooperative experiment is designed to serve as a prototype for large-scale seismic experiments in the interior of Antarctica in the next decade. Broadband seismic imaging of lithospheric structure: application to the Transantarctic Mountain front and Bentley Subglacial Trench Daniel R.H. O'Connell, Ohio State University (S-165) The tectonic relationship between the east antarctic Precambrian craton and the west antarctic assemblages of deformed Paleozoic sedimentary rocks, Jurassic granites, and Mesozoic and Cenozoic intrusive and extrusive rocks remains a fundamental problem of Gondwanaland geology. To explore this question, this study will focus on determining the lithospheric signature of the Bentley Subglacial Trench in West Antarctica. Investigators will deploy an array of portable, digital broadband seismographs at a Beardmore Glacier site and at a site close to the Bentley Subglacial Trench. Seismic waveform modeling of broadband body waveforms will be used to describe constraints on Transantarctic Mountain and Bentley Subglacial Trench lithospheric velocity structures. Further, the portable seismic packages used in this project will provide a long-term capability for studying lithospheric structure throughout the antarctic interior. Oxygen-isotope climate record from McMurdo dome and its relation to the geological climate record of the McMurdo Dry Valleys Pieter M. Grootes, University of Washington (S-167) During this study, investigators will obtain a climate record of the Holocene and the last part of the last glaciation from the McMurdo dome, a small ice dome near the head of Taylor Valley in southern Victoria Land. Comparison of this isotope proxy climate record with a radiocarbon-dated proxy record derived from perched deltas, strandlines, and moraines in the nearby McMurdo Dry Valleys will provide data that could be crucial for interpreting both the isotopic oxygen-18 fluctuations observed in ice cores during the Holocene and the lake levels and ice positions during this time. These comparisons should reveal the response of the east and west antarctic ice sheets to the glacial-interglacial temperature increases and sea-level rise. HUMAN BIOLOGY AND MEDICINE The influence of prolonged polar residence on the cellular distribution of thyroid hormones H. Lester Reed, U.S. Naval Medical Research Institute (S-030) Thyroid hormones are important for maintaining basal metabolism; however, adaptations to the environment can alter the concentrations of these hormones. Data from earlier investigations have shown that thyroid activity changes after prolonged residence in
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United States Antarctic Research: Report No. 32 to the Scientific Committee on Antarctic Research (SCAR) 1 April 1989 - 31 March 1990 Antarctica. In a 1986 study, investigators found that after 42-weeks residency in Antarctica, the responsiveness of the pituitary that stimulates thyroid activity to the hypothalamic-releasing hormone (TRH) increased by 50 percent. Additionally, the rate of production of another thyroid-related hormone (triiodothyronine or T3), the rate of metabolic clearance, and the volume of distribution increased by 150, 160, and 230 percent, respectively, when compared with a control group. How these changes occur and what physiological and psychological significance they have is yet unknown. By continuing the earlier investigation, researchers hope to begin answering these questions. They will investigate human circulating blood lymphocyte as a model for human-tissue response to alterations in thyroid hormones found after prolonged antarctic residency. From blood samples taken from 20 volunteers, the investigators will isolate circulating lymphocytes, which reflect accurately system-wide thyroid activity at the tissue level. Sampling will be done before, during, and after the volunteers have been in Antarctica for 42 weeks. To determine the concomitant cellular and sub-cellular changes that are associated with changes in peripheral T3, the volume of distribution, the T3-production rates, and the metabolic clearance rates, investigators will analyze these lymphocytes for alterations in the T3 receptor number and affinity and in RNA. OCEAN PHYSICAL SCIENCES Antarctic bottom water formation Theodore D. Foster, University of California at Santa Cruz (S-206) This project will investigate the dynamics and processes of deep-water formation in the western Weddell Sea, combining physical and chemical oceanographic techniques to produce a coherent picture of the importance of this unique region to the structure of the world ocean. In the global context, this area is a major water mass modification site, involving open-ocean convection, the continental margin, and the ice cover. At this time, the various water types that combine to form Weddell deep water and Antarctic bottom water and the conditions under which these water masses form are not known well enough to establish direct physical links and volumetric budgets. Investigators expect that the outflow from the Weddell Sea is restricted to quite narrow boundary currents flowing near the base of the continental shelf and, consequently, could be observed with conventional current-meter moorings from the shelf into the deep ocean. Two oceanographic expeditions to the western Weddell Sea are planned as part of this study. The objectives will be to measure the flow of the newly-formed bottom water and to explore the sinking process of the near-surface waters in the open ocean to see how these affect the deep water flows. Marine geology of the Antarctic Continental Margin John B. Anderson, Rice University (S-207) Since 1979, scientists have collected and described sediments that blanket the antarctic seafloor; with these data, they have related sedimentary facies to glacial and oceanic conditions. During the 1990-91 austral summer, investigators will gather seismic reflection data and collect piston core samples in the Bransfield basin (north of Palmer Station to King George Island) and along the continental margin (north of the South Shetland Islands). Working aboard the Polar Duke, they will use sedimentologic analysis of deposits and high-resolution seismic methods to map the distribution of marine ice sheets and ice shelves on the continental shelf during the last glacial maximum. By detailed study of lithofacies in areas representative of antarctic glacial-marine environments, scientists will increase their understanding of glacial-marine sedimentation.
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United States Antarctic Research: Report No. 32 to the Scientific Committee on Antarctic Research (SCAR) 1 April 1989 - 31 March 1990 Additionally, they will examine the deep-sea hemipelagic and turbidity record to see how glacial changes are manifested in deep-sea deposits and conduct high-resolution seismic stratigraphic studies of the continental shelf to learn more about tectonic and glacial evolution. This year's work and the results of studies conducted over the last 11 years will be combined and published as a folio series on the Antarctic Continental Margin. Sinking and suspended particulate matter on the antarctic continental margin Robert B. Dunbar, Rice University (S-216) As much as 25 to 40 percent of silica in the southern oceans may be removed through sedimentation on the continental shelf. Despite high levels of oxygenation in the water column, organic carbon accumulates at high rates, often equal to those found in low-latitude basins lacking oxygen. The processes producing such widespread and rapid deposition are poorly understood. Surface-water production appears relatively low over most of the area most of the time. High production does occur within and below the sea ice, but few sea-ice diatoms are preserved on the seafloor. Large-scale productivity in the open ocean has been recorded from December through January but not studied in detail. The objective of this study is to resolve the major features of the carbon and silica cycles along the continental shelf in the western Ross Sea area. Investigators will examine the vertical flux and water column dissolution/decomposition of opal and organic matter as part of a multidisciplinary investigation with investigators from North Carolina State University (S-268). From the Polar Sea, time-series sediment traps, current meters, and transmissometer arrays deployed during the 1989-90 austral summer will be recovered. These arrays, which will be redeployed, enable investigators to measure and characterize both vertical and horizontal fluxes of particulate debris during a complete annual cycle of production and sedimentation. From these data and those obtained by other researchers, they will quantitatively assess surface-, mid-, and deep-water column processes that determine sedimentation rates on the antarctic continental shelf. The results of this study should improve understanding of the influence of antarctic shelf sedimentation on ocean chemistry, as well as our ability to interpret the shelf sediment record from the last glacial period during the Pleistocene epoch. Sources and fluxes of biogenic and anthropogenic carbon compounds in antarctic marine sediments M.I. Venkatesan, University of California at Los Angeles (S-219) Preliminary organic geochemical data from antarctic sediment cores indicate that organic matter in Holocene sediments is well preserved. Information regarding the occurrence, source, and preservation of several lipid components, however, is lacking. In this project, investigators will undertake detailed geochemical analyses of free and bound lipids from sediments and particulates and of total lipids from the potential source materials. It is their goal to characterize the sources, estimate the fluxes, and to study the incorporation of organic compounds into seafloor sediments. These data should help scientists understand the paleoceanographic conditions and biogeochemical processes in the region by resolving sediment provenance; identify chemical tracers of global pollution by providing a baseline measurement for future monitoring studies; and evaluate the historical migratory routes and habitats of marine mammals (particularly, cetaceans and pinnipeds) in the region. Significance of bacterial exoenzymes in organic matter cycling in the Southern Ocean James T. Hollibaugh, University of California at San Diego (S-230) Coupling of carbon flows from primary producers to bacteria can significantly influence
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United States Antarctic Research: Report No. 32 to the Scientific Committee on Antarctic Research (SCAR) 1 April 1989 - 31 March 1990 the patterns of vertical flux of organic matter in the ocean. Bacteria must breakdown particles and mix them with water before uptake; thus, excreted enzymes (bacterial exohydrolases) assume a central role in carbon flux from particulate organic matter into the microbial loop. Investigators hypothesize that during the austral winter, bacterial-exohydrolase production ceases in the high latitudes. Therefore, particles and polymers produced during the early spring bloom cannot be used by bacteria. Investigators will test this hypothesis in the waters off Palmer Peninsula, where they will sample the euphotic zone pre-bloom through the development and decline of the spring phytoplankton bloom. Field and laboratory manipulations will examine environmental cues that regulate enzyme activity. This knowledge should contribute to the understanding of biological production mechanisms and variability in the pathways of organic matter cycling in the Southern Ocean. Preservation and accumulation of biogenic silica and organic carbon in a high-latitude environment: the Ross Sea David J. DeMaster, North Carolina State University (S-268) Antarctic deep-sea and continental shelf environments are the world's major repository for silica in the marine environment. Annually, about 75 percent of all silica deposited in the world's oceans by rivers and hydrothermal emanations occurs in antarctic waters; however, antarctic sediments account for less than 10 percent of the global organic-carbon budget. A significant element of the differences in these two global budgets may relate to how efficiently the water column and seabed preserve particulate material. Continuing an investigation begun during the 1989-90 austral summer, investigators will measure rates of production in surface waters, water-column regeneration, vertical flux, seabed regeneration, and accumulation to determine the preservation efficiency for silica and carbon fluxes in the Ross Sea. They will collect various types of cores from sediments in the northwest and southwest Ross Sea and will measure pore-water profiles of dissolved silica, total dissolved carbon dioxide, nitrate, nitrite, ammonia, sulfate, and phosphate to evaluate biogenic silica dissolution and organic matter degradation in the seabed. By using radiochemical chronologies and biogenic-silica and organic-carbon measurements, investigators hope to determine silica and organic-carbon accumulation rates. In addition to collecting and redeploying current meters and transmissometers installed last year, they will use towable seismic instruments to obtain profiles of the seafloor. Depositional processes and stratigraphy of antarctic fjords and ice-shelf environments Eugene W. Domack, Hamilton College (S-285) This project is a study of sediment transport on the antarctic continental margin near floating glacier tongues and restrictive fjord environments. It is concerned with determining the importance of mid-water and deep-cold-water tongues in the transport processes, and whether precise links can be established between the observed glacial-climatic regime and the resulting depositional record. The depositional record will be reconstructed from a coring program and from high-resolution seismic reflection profiles. The expected thick Holocene sections, with pronounced internal changes in texture and composition, will be analyzed for their implications with respect to the responses of antarctic fjord glacier systems to Holocene climate changes. The field work will be carried out on the Antarctic Peninsula.
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United States Antarctic Research: Report No. 32 to the Scientific Committee on Antarctic Research (SCAR) 1 April 1989 - 31 March 1990 Physical properties and structural stratigraphic variation of frazil, platelet, and congelation sea ice, Ross Sea, Antarctica Martin O. Jeffries, University of Alaska (S-290) Frazil ice may play a key role in the complex Southern Ocean regime, yet the formation, growth, and behavior of frazil ice in both horizontal and vertical dimensions are the least understood components of the ocean/sea-ice system. Investigators will examine the physical and structural properties of antarctic sea ice to determine the quantities of frazil, platelet, and congelation ice in Ross Sea pack ice. With these data, investigators will determine whether frazil, platelet, and congelation ice have different levels of salinity, and whether observed salinity variations are related to ice structure and stratigraphy. Additionally, they will document grain size and structure variations in frazil and platelet ice, examine their relationships to ice salinity, and complete a detailed study of the substructure of frazil and platelet ice to determine how and where brine and other materials are included and subsequently lost from the ice. Ice cores will be tested for salinity and temperature, as well as analyzed by thick/thin section techniques for structural and stratigraphic variations. Ice crystal size and structure variations will be studied using optical and scanning electron microscope techniques.
Representative terms from entire chapter: