极地研究

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CHARACTERISTICS OF THE INITIAL DENSIFICATION PROCESSES OF SNOW/FIRN IN WILKES LAND,ANTARCTICA

Qin Dahe, N. W. Young

1991, 2 (1-English): 1-9.

摘要 ( 1035 )

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14 shallow snow / firn cores were taken by drilling with the PICO lightweight hand coring auger on Law Dome and Wilkes Land along a line approximately 111 °E longitude between 66°S and 74°S latitude. 5 of these cores, BJ, LJ24, GC30, GC40 and GC46, 20-30 m deep, are studied in detail in this paper. The densities of snow / firn were measured in a cold room at temperature between -18℃ and-14℃ by taking consecutive core samples and weighing the mass of each sample whose volume was known. The characteristics of the initial densification (till a density of 550 kg / m3) including the variation of snow / firn density with increasing depth, densification rate of snow / firn and the com-pactive viscosity coefficient of snow / firn are studied, and the factors affecting this initial densification process are discussed. From the obtained measurements, a relationship between compactive viscosity coefficient of snow / firn and mean annual temperature is found in case ρ=550 kg / m3 . For snow / firm on Wilkes Land, the relationship we found at a mean annual temperature below -25℃ (i.e. no melting features are present in stratigraphy) is very similar to that found by Nishimura and others (1983) on Mizuho Plateau, Antarctica.

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SURFACE MASS BALANCE AND ITS VARIATION ON THE MIZUHO PLATEAU, ANTARCTICA IN 1987-1988

Zhang Wenjing, Takashi Yamanouchi

1991, 2 (1-English): 10-21.

摘要 ( 978 )

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From the surface mass accumulation data in year of 1987 / 88, the distribution and variation of annual mass balance on Mizuho Plateau are discussed. The authors also analyze the effects of short-term climatic and topographical variations on the mass balance. It is found that there are some differences in spatial distribution and annual average state in the year of 1987 / 88 and other years. In the area at elevation lower than 550m near the coast, the mass balance appears to be negative. The annual mass balance over 80 km distance from S16 to inland is 0.84m snow depth. A low mass balance zone from 80 km site to Mizuho Station, is considered to be only 0.14 m snow depth. It is found from the comparison of mass balances that the mass-balance level on the glaciers in West China is 9 times higher than that on Mizuho Plateau, where the massbalance level appears to be low accumulative and low expensive, but inverse in middle and low latitude regions, such as on glaciers in West China. The effects of short-term climatic and topographical variations or the mass balance are more significant in this year than mean state in many years. In the high accumulation zone the effect of the short-term climatic variation is larger than that of topographical one, while in the low value zone the topographical effect is larger than the climatic variation.

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REPEATED COMPRESSION-ANNEALING EXPERIMENTS ON ANISOTROPIC CORE ICE

Huang Maohuan, Wang Wenti, Li Jun, Li Gang

1991, 2 (1-English): 22-29.

摘要 ( 1031 )

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Three runs (6 samples) of repeated uniaxial compressionannealing experiments were conducted on a creep testing machine with a loading accuracy of 1 % at-2±0.2℃. The tested samples were cut from BHQ ice core. Compression axes were parallel, at an angle of 45°and normal to the vertical of the core respectively. The initial orientation fabrics of samples were single-maximum pattern or approximate single-maximum pattern with different mean grain size. The sample was compressed with an initial axial stress of 0.8 MPa, until 10% axial strain was obtained, and then annealed for 72 hours. Such compression-annealing procedure was lepeated 6 times for a run. The experimental result shows that under a warm temperature and large load, the initial features of structure and fabric disappear finally, and n small circle girdle fabric with fine equigranular grains appears, and a multi maxima fabric developes to seme extent. Analysis of structure and fabric shows that the formation mechanism of new fabrics in these experiments is principally recrystallization. With the repetition of compression-annealing, the difference in the fabric of the six samples is reducing, their rheological behavior tends to be uniform, and their grain size decreases towards a steaty state value.

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SYSTEMATIC COVARIATION OF SR, BA, CA ELEMENTS IN CENOZOIC VOLCANIC ROCKS ON THE FILDES PENINSULA, WEST ANTARCTICA, AND ITS RELATION TO PEIROGENESIS

Zheng Xiangshen, Liu Xiaohan

1991, 2 (1-English): 30-38.

摘要 ( 1078 )

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Cenozoic volcanic rocks in the Fildes Peninsula are composed of High-Al basalt, basaltlc andesite, andesite, and dacite belonging to a calc-alkaline volcanic series with low-K and high-A1 characteristics. Using a new indicator, the Sr/Ca-Ba/Ca, systematics proposed by Onuma (1980, 1981) and Sr, Ba, Ca concentrations in volcanic lavas and subvolcanic rocks, the authors find that the high-A1 basaltic volcanic rocks either in volcanic strata or in subvolcanic intrusives were formed from a primary magma, in different stages through the fractional crystallization of clinopyro-xene(Cpx)and plagioclase (P1) in the process of magmatic evolution, resulting in the formation of basaltic-andesitic, andesitic and dacitic rocks.

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ECOLOGICAL OBSERVATIONS ON COLOURED LAYER OF COASTAL FAST ICE IN GREAT WALL BAY, KING GEORGE ISLAND, ANTARCTICA

Lu Peiding, Zhang Kuncheng, Huang Fengpeng, Kentaro Watanabe

1991, 2 (1-English): 39-45.

摘要 ( 864 )

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Marine biological and environmental investigations were carried out on the coastatl waters off Great Wall Station (62°13's, 58°58'W) on King George Island, Antarctica, from November 17, 1988, to March 3,1989. Coastal fast ice covered inner part of Great Wall Bay until mid-December 1988, which allowed us to take ice core sampling and observations from mid-November to early December 1988. During this period, ice thickness ranged from 90 to 70cm with baout 20cm of snow cover. About 5cm brown layer occured in the middle part of fast ice core collected on November 20, 1988 at site 2, and two brown layers occured in the interior of ice core collected on November 17,20 and 26, 1988 at site 5. In comparison to the water column, chlorophyll-a concentration in fast ice was higher, which ranged from 2.55 to 56.84mg/m8, and most of them were concentracted in the interior layers of sea ice rather than in the bottom layer often observed in other sea ice areas, such as in Syowa, Davis, Casey Station and McMurdo Sound areas, etc. This might be a result of the difference in structure and formation procese of sea ice. Meanwhile, temperature, transparency, nutrients and chlorophyll-a in water column were measured. Microalgal assemblages both in fast ice and water column of Great Wall Bay were reported.

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THE POLAR IONOSPHERE AND THE MAGNETOSPHERE-IONOSPHERE COUPLING

Zi Minyun, Shen Changshou

1991, 2 (1-English): 46-52.

摘要 ( 956 )

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EISCAT (the Incoherent System at the northern polar region) data are used in discussion of the magnetosphere-ionosphere coupling. Comperison between samples in geomagnetic quiet days and during magnetic storms shows a significant effect of the basic magnetospheric processes on the features of the polar ionosphere. It not only demonstrates that the polar ionosphere can be regarded as a 'panoramic screen' of these process, but also indicates an importance of the simultaneous observation of southern and northern polar regions (especially, at the magnetic conjugate points). A few topics concerned are suggested for the further study of the southern polar region.

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CHARACTERISTICS OF Sq VARIATION OF GEOMAGNETIC FIELD AT THE GREAT WALL STATION, ANTARCTICA IN WINTER

Liu Changfa, Zhang Ping, Jiao Chengmin

1991, 2 (1-English): 53-59.

摘要 ( 818 )

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In this paper the characteristics of Sq variation of geomagnetic field in the region of the Chinese Great Wall Station (CGWS), Antarctica, in winter are analyzed from geomagnetic data obtained at the Geomagnetic Observatory of CGWS. The result enables us to reveal the following aspects: (1) The pattern of Sq variation at CGWS in early (Apr.) and Late winter (Sep.) is similar to that at Beijing Geomagnetic Observatory (BJO) at the middle latitude in the Northern Hemisphere. It may be controlled by the midlatitudinal ionospheric dynamo current. Amplitude of Sq variation is very small, and the harmonics in 8 hours or shorter periods in midwinter (June and July) is predominant because of the decreased effect of solar ultraviolet radiation and the dominant geomagnetic disturbance at high latitudes. (2) The vectors of Sq-equivalent current in the daytime are about five times more than that in the night. The direction of the vectors is clockwise in the daytime (08-15h) and counterclockwise in the night in early and late winter. Both of the vectors are very small because of the effect of the current density in the ionosphere is relatively weak in midwinter. The direction of vectors of Sq-equivalent current at CGWS in early and late winter is different from that in midwinter. It may be affected by the ionospheric current and field-aligned current in the polar region.

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HF FIELD STRENGTH MEASUREMENTS OVER THE VERY LONG DISTANCE

Du Junhu, Sun Xianru

1991, 2 (1-English): 60-67.

摘要 ( 824 )

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It was ascertained that there is a great margin between the theoretical values and experimental medians of the field strength of RWM and RID signals during high solar activity period at Chinese Great Wall Station on Antarctica. The calculated values are, on average, less than the experimental, especially on the propagation path between RID and Antarctica. The field strength by the experiment may be used as the basic data for the research of HF propagation over the very long distance. Because of the large deviation it seems to be necessary to study HF propagation over the very long distance in details, especially the propagation model.

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