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Measurements are presented of the neutral wind field in the lower thermosphere over Mawson, Antarctica, made during the austral Spring of 1981. The Mawson Institute's Fabry-Perot spectrometer was used to study the OI lambda 588 nm emission in the night airglow and aurora. Wind velocities were inferred from Doppler shifts of this emission.
The 50-MHz Doppler radar installed at Syowa Station (69 deg 00'S, 39 deg 35'E), Antarctica, in 1982 can detect continuously a meteor echo if an operator assigns the meteor mode operation to the radar. The radar has two narrow antenna beams (4 deg in the horizontal plane), one toward geomagnetic south and the other toward approximately geographic south, with a crossing angle of about 33 deg. The minicomputer annexed to the radar controls the transmission and reception of a 50-MHz wave. If the receiver detects a meteor echo, the flag signal is sent to the computer. Then the computer begins to determine the echo range with a time resolution of 1 micro s and to sample every 200 microns/s for 1 s the Doppler signal and echo intensity at the particular range (R). The line-of-sight velocity (V sub D) of the echo trail is calculated from the output from the Doppler signal detection circuit having an offset frequency by using the so-called zero-crossing method. The echo amplitude decay time calculated by a least-mean square method is used to obtain the ambipolar diffusion coefficient (D) and then to calculate the echo height (H). About 120 day observations were made during 1982-1983. Some early results are presented. magnetic tapes together with V sub D, D, H and R for later analysis in Japan. About 120 day observation were made during 1982-1983. Some early results are presented.
Extensive attention has been directed to nitrogen dioxide (NO2) since its important role in the atmospheric chemistry relating to the stratospheric ozone (e.g., WMO, 1982) has been pointed out. However, the behavior of NO2 in the atmosphere has still not been fully confirmed, although ground-based, balloon and satellite measurements of NO2 have been reported by many scientists. Especially, only a few measurements made at high latitude in the Southern Hemisphere have been reported. The total atmospheric NO2 by ground-based visible absorption spectroscopy at Syowa Station (69 deg S, 39.6 deg E), Antarctica. The observation continued from March 1983, to January 1984. The principles of measurement, instrumentation and the method of data analysis are described in detail.
The mesospheric sodium layer has been observed at Syowa Station in Antarctica during the wintering period of the 26th Japanese Antarctic Research Expedition. A lidar observation of the polar middle atmosphere at the station has been performed as a part of the Middle Atmosphere Program since 1983. At first stratospheric aerosols have been observed by the system based on a ruby laser. In 1985 a new transmitting system consisting of a tunable dye laser was added to that system to observe the sodium layer, too. The characteristics of the lidar system are given. The results of the mesospheric sodium layer observed on 42 nights during the period from March to October, 1985 are also given.
Physical conditions in the 10-20 km region of the Antarctic stratosphere make the (NO2)/(NO) ratio particularly sensitive to high chlorine levels in the form of ClO. According to simple known photochemical relationships between NO2, NO, ClO, and O3, high ClO levels of 1 ppbv over Antarctica must be accompanied by large values of the (NO2)/(NO) ratio. At high ClO abundances, the (NO2)/(NO) ratio is approximately proportional to the ClO concentration. It is proposed that in-situ measurements of the (NO2)/(NO) ratio could be used to test the high chlorine hypothesis.
Data collected in the region of the mouth of ice stream B, West Antarctica, during three field seasons are presented. The physical characteristics of the mouth of ice stream B are described, and the dynamics in the vicinity of the DNB network are discussed. The dynamics of ice stream B from DNB to the grounding line is briefly considered, and a force analysis of the grounding line region is made. The results demonstrate that the dynamic situation of the region at the mouth of ice stream B is distinctly different from either the greater portion of the ice stream upstream or the Ross ice shelf downstream.
In the austral spring of 1986, a program of measurements of the ozone altitude profile (for the z values between 25 and 55 km), relevant to an understanding of the ozone hole, was conducted at McMurdo Station, Antarctica. The measurements were performed using ground-based millimeter-wave spectrometry. It was found that the ozone mixing ratio peaked at altitudes ranging from 28 to 34 km, with peak values between 5 and 9 ppm by volume. During the period between September 12 and October 29, the ozone mixing ratio decreased, with great variability, by about 15 percent at 25 km, with no significant decrease at higher altitudes. The observation of the depletion occurring only below 25 km is consistent with ozone-sonde observations during previous years.
Petrological data on mesosiderites from Reckling Peak (RKP) and Allan Hills (ALH), Antarctica, are presented. The results suggest that the Allan Hills mesosiderites A77219, A81059, and A81098 are probably paired (being of similar texture, modes, and mineral composition), and ALHA 81208 is, most likely, a clast from one of these mesosiderites. RKPA 80258 is a weakly poikilitic plagioclase-poor mesosiderite, completely different from ALHA 77219, 81059, and 81098. On the other hand, RKPA 79015, 80229, 80246, and 80263 are very similar, belonging to subgroup C diogenitic mesosiderites. These mesosiderites contain orthopyroxene and recrystallized orthopyroxenite clasts in a metal-troilite matrix. The silicate fraction of mesosiderites ranged from diogenitic (RKPA 79015) to analogous to polymict eurcrite (Dyarrl Island). On the basis of petrologic data, the mesosiderite subdivision scheme was amended, making it possible to classify the formerly 'anomalous' RKPA 79015.
This report presents data collected during three field seasons of glaciological studies in the Antarctica and describes the methods employed. The region investigated covers the mouths of Ice Streams B and C (the Siple Coast) and Crary Ice Rise on the Ross Ice Shelf. Measurements included in the report are as follows: surface velocity and deformation from repeated satellite geoceiver positions; surface topography from optical levelling; radar sounding of ice thickness; accumulation rates; near-surface densities and temperature profiles; and mapping from aerial photography.
The lunar Dobson observation is almost the only way to get the total ozone in or around the polar night season at high latitudes where the total ozone observation by solar Dobson is not available. The total ozone observations by lunar Dobson were carried out at Syowa Station (69 S, 40 E), Antarctica in 1969, and 1982 to 1986, in the months from March to October. The method, the accuracy and the results of the lunar Dobson observation carried out at Syowa Station from 1982 to 1986 are described.
The Total Ozone Mapping Spectrometer (TOMS) instrument on the Nimbus-7 satellite provides the primary source of total ozone data for the study of total ozone in the polar regions of the earth. There are two types of instrument related errors: a slowly developing drift in the instrument calibration since the launch of the instrument in October 1978 and an increase in the measurement noise beginning April, 1984. It is estimated that by October 1987, the accumulated error in the TOMS total ozone measurement due to instrument drift is about 6 m-atm-cm. The sign of the error is such that the TOMS is slightly overpredicting the long-term decrease of the Antarctica ozone. The increase in the measurement noise is more difficult to quantify, affecting some measurements by as much as 10 D.U. and others not at all. A detailed analysis of this error and its potential impact on the studies of total ozone from TOMS will be provided. There are three categories of algorithmic errors: (1) error due the unusual shape of the ozone profile in the ozone hole; (2) error caused by very low atmospheric temperatures in the ozone hole affecting the ozone absorption cross-sections at the TOMS wavelengths; and (3) errors resulting from occasionally thick stratospheric clouds that sometimes reach to 20 km in the ozone hole.
NASA's Goddard Space Flight Center/Wallops Flight Facility conducted a series of 52 balloon-borne measurements of vertical ozone profiles over the National Science Foundation (NSF) research facility at Palmer Station, Antarctica (64 deg 46 S, 64 deg 3 W) between August 9 and October 24, 1987. High resolution measurements were made from ground level to an average of 10 mb. While much variation was seen in the profile amounts of ozone, it is clear that a progressive depletion of ozone occurred during the measurement period, with maximum depletion taking place in the 17 to 19 km altitude region. Ozone partial pressures dropped by about 95 percent in this region. Shown here are plotted time dependences of ozone amounts observed at 17 km and at arbitrarily selected altitudes below (13 km) and above (24 km) the region of maximum depletion. Ozone partial pressure at 17 km is about 150nb in early August, and has decreased to less than 10nb in the minimums in October. The loss rate is of the order of 1.5 percent/day. In summary, a progressive depletion in stratospheric ozone over Palmer Station was observed from August to October, 1987. Maximum depletion occurred in the 17 to 19 km range, and amounted to 95 percent. Total ozone overburden decreased by up to 50 percent during the same period.
SRI International operated a dual wavelength (1.064 micrometer and .532 micrometer) aerosol lidar at McMurdo Station, Antarctica, as part of the National Ozone Expedition-2 (NOZE-2). The objective of the project was to map the vertical distributions of polar stratospheric clouds (PSCs), which are believed to play an important role in the destruction of ozone in the Antarctic spring. Altitude, thickness, homogeneity, and duration of PSC events as well as information on particle shape, size or number density will be very useful in determining the exact role of PSCs in ozone destructions, and when combined with measurements of other investigators, additional properties of PSCs can be estimated. The results are currently being analyzed in terms of PSC properties which are useful for modeling the stratospheric ozone depletion mechanism.
There have been a large number of suggestions made concerning the origin of the Antarctic 'ozone hole' since its discovery; these changes include stratospheric chemistry, or changes in the solar input, or combinations of these effects. Supporting or refuting these theories requires a wide variety of data for comparison with the predictions. In Aug. and Sept., 1987, a field observation expedition was made over Antarctica from a base in Punta Arenas, Chile. Two aircraft, an ER-2 with in-situ instruments flew at altitudes up to 18 km measuring ozone, water, ClO, BrO, NO sub x, particles, and meteorological parameters in the ozone layer. A DC-8 flew at altitudes of 10 to 12 km, below the ozone layer, using remote sensing instruments for measuring composition and aerosol content of the ozone layer, as well as in-situ instruments for measuring composition at aircraft altitudes. The obsevation of a number of chemical species and their correlation with each other and with meteorological parameters gives a useful set of data for comparison with various theories.
Ways of stopping the ozone depletion in the ozone hole over Antarctica were studied. The basic objectives were: (1) to define and understand the phenomenon of the ozone hole; (2) to determine possible methods of stopping the ozone depletion; (3) to identify unknowns about the hole and possible solutions. Two basic ways of attacking the problem were identified. First is replenishment of ozone as it is being depleted. Second is elimination of ozone destroying agents from the atmosphere. The second method is a more permanent form of the solution. Elimination and replenishment methods are discussed in detail.
Dust bands on blue ice fields in Antarctica have been studied and have been identified to originate from two main sources: bedrock debris scraped up from the ground by the glacial movement (these bands are found predominantly at fractures and shear zones in the ice near moraines), and volcanic debris deposited on and incorporated in the ice by large-scale eruptions of Antarctic (or sub-Antractic) volcanoes. Ice core studies have revealed that most of the dust layers in the ice cores are volcanic (tephra) deposits which may be related to some specific volcanic eruptions. These eruptions have to be related to some specific volcanic eruptions. These eruptions have to be relatively recent (a few thousand years old) since ice cores usually incorporate younger ice. In contrast, dust bands on bare blue ice fields are much older, up to a few hundred thousand years, which may be inferred from the rather high terrestrial age of meteorites found on the ice and from dating the ice using the uranium series method. Also for the volcanic ash layers found on blue ice fields correlations between some specific volcanoes (late Cenozoic) and the volcanic debris have been inferred, mainly using chemical arguments. During a recent field expedition samples of several dust bands found on blue ice fields at the Lewis Cliff Ice Tongue were taken. These dust band samples were divided for age determination using the uranium series method, and chemical investigations to determine the source and origin of the dust bands. The investigations have shown that most of the dust bands found at the Ice Tongue are of volcanic origin and, for chemical and petrological reasons, may be correlated with Cenozoic volcanoes in the Melbourne volcanic province, Northern Victoria Land, which is at least 1500 km away. Major and trace element data have been obtained and have been used for identification and correlation purposes. Recently, some additional trace elements were determined in some of the dust band samples, including Ir. Iridium determinations were made using INAA, with synthetical and natural (meteorite) standards. These findings are discussed.
Rare vitric volcanogenic ash but more abundant clay minerals considered volcanogenic in origin are associated with an expanded and essentially complete K-T boundary sequence from Ocean Drilling Project (ODP) Hole 690 C on Maud Rise in the Weddell Sea off East Antarctica. Results at this writing are preliminary and are still based to some extent on shipboard descriptions. Further shore-based studies are in progress. It would appear, however, that the presence of volcanic ash and altered ash in the Danian section beginning at the biostratigraphically and paleomagnetically determined K-T boundary on Maud Rise can be cited as evidence of significant volcanic activity within the South Atlantic-Indian Ocean sector of the Southern Ocean coincident with the time of biotic crises at the end of the Maestrichtian. This is a postulated time of tectonic and volcanic activity within this Southern Hemisphere region, including possible initiation of the Reunion hot spot and a peak in explosive volcanism on Walvis Ridge (1) among other events. A causal relationship with the biotic crisis is possible and volcanism should be given serious consideration as a testable working hypothesis to explain these extinctions.
It is possible to hypothesize that, if microbial life evolved on early Mars, fossil remnants of these organisms may be preserved on the surface. However, the cooling and drying of Mars probably resembled a cold desert and such an environment is not suitable for the process of fossilization. The frigid Ross Desert of Antarctica is probably the closest terrestrial analog to conditions that may have prevailed on the surface of the cooling and drying Mars. In this desert, cryptoendolithic microbial communities live in the airspaces of porous rocks, the last habitable niche in a hostile outside environment. The organisms produce characteristic chemical and physical changes in the rock substrate. Environmental changes (deterioration of conditions) may result in the death of the community. Although no cellular structures are fossilized, the conspicuous changes in the rock substrate are preserved as trace fossils. Likewise, microbial trace fossils (without cellular structures) may also be preserved on Mars: Discontinuities in structure or chemistry of the rock that are independent of physical or chemical gradients may be of biological origin. Ross Desert trace fossils can be used as a model for planning search strategies and for instrument design to find evidence of past Martian life.