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    30 June 1988, Volume 1 Issue 2 Previous Issue    Next Issue

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    THE HISTORY OF SPREADING OF DARKE PASSAGE AND ITS EFFECTS
    1988, 1 (2):  1-7. 
    Abstract ( 1337 )   PDF (473KB) ( 1680 )  

    In the paper the histroy of spreading of Darke Passage and its effects on Antarctic circumpolar current are discussed basing on the geophysical data obtained during first Chinese Antarctic Expedition. The spreading direction of Drake Passage is NW-SE. The spreading process could be distinguished into three stages: first stage was in 28-24 Ma B.P., the second in 24-16 Ma B.P. and the third in 16-8 Ma B.P. The spreading rates are 2.5cm/a, 1.8cm/a, and 1.0 cm / a repectively. The West Antarctica was separated form the South America by the spreading of Drade Passage. It is the last important geological event in Gondwanaland fragmertation. The Antarctic circumpolar current was formed in 24 Ma B.P. The development of the current was restrited by Shackleton Fault Zone. The current prevents warm current from Equator. Thus, it is the main cause for that the temperature of Antarctic continent became very cold.

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    CHEMICAL WEATHERING IN PERMAFROST REGIONS OFANTARCTICA——GREAT WALL STATION. CASEY STATION AND DAVIS STATION AREAS
    1988, 1 (2):  8-14. 
    Abstract ( 1323 )   PDF (482KB) ( 1393 )  

    Although it is cold and dry in permafrost region of Antarctica, chemical weathering and ion migration do occur. CaCO3 is leached downwards and deposited at a depth of about 1m in Great Wall Station area. Chemical weathering is stonger in the Great Wall Station area then in the Casey and Davis areas. This paper deals with the chemical weathering process of bed rocks in some areas of Antarctica. The samples were collected from the areas of the Great Wall Station of China by Xie Youyu and Zhan Qingsong in 1984 to 1986, Casey station by Xie Zichu in 1984 and the Davis station by Zhang Qingsong in 1980. We have known that types of weathering crust in different rareas by correlation analysis of the chemical elements, the characteristics of enrichemnt and migration of the elements in weathering process, the influence of grain size on element migration and clay minerals and the absorption of rare elements. (1) Great Wall Station area. According to the analysis of aggregation and dissemination of elements, it is known that some elements change from bottom upwards, such as the cation exchange capacity, which is a best indicator reflecting weathering intensity; contents of K, Na, Ca, and Mg all had dispersed during the weathering process, but Co, Ti, Fe and Mn are all concentrated upward. The content of CaCO3 is high at a certain depth. As mentioned above, an obvious differentiation of elements occurred in the weathering crust of volcanic andesite-basaltic agglomerate and tuff in this area. It appears that there is a stratified weathering crust type and can be named the carbonate-stratified weathering crust. (2) Davis Station Area. The distribution and migration of elements indicate that the chemical weathering process does occur in such a polar area, although it is rather weak and an initial stage, there is a tendency that the debris weathering crust is changing to the silica-alminium-chloride type. The weathering crust there can be termed the debris-carbonate type of weakly weathering crust. (3) Casey Station Area.There is no any secondary CACO3 in sediments and the weathering crust in Casey Station area. The content of soluble salt is also very low, 0.03 to 0.11% in salinity. It can be concluded that this area is still in an initial stage of weathering with a debris type of weathering crust.

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    SWARM STRUCTURE OF ANTARCTIC KRILL (Euphausia Superba DANA) IN WATER NORTHEAT OF KING GEORGE ISLAND, JANUARY 1985
    1988, 1 (2):  15-21. 
    Abstract ( 1512 )   PDF (553KB) ( 1147 )  

    During the First Chinese Antarctic Expedition, in water northeast of King George Island krill (Euphausia superba Dana) swarms were found and observed by echosounder (200 kHz) , and 15 IKMT (Isaacs-Kidd midwater trawl) tows were made in an area of 3 x 5 nautical mile. The population structure of 6 samples were analysed by means of L-F distribution and sexual maturity stage composition. The percent similarity indices of L-F distribution between samples are very high, 84.3% in average. That of sexual maturity stage composition is 75.6% in average. The population structures inside the searched area are quite similar. Echograms show that the swarms are distributed mainly in a layer at 20-50 m depth. Its upper limit is quite stable, but the lower limit varies greatly according to the thickness of the swarm. The highest density observed is 4418 individuals/ 1000 cubic meter, . only 1400 individuals / 1000 cubic meter in average, and much lower than that of swarms commercially harvested. The temperature of water in which swarms occurred ranges from 0.85 to 1.65℃, and the salinity 34.003-34.163‰. Adults constitute the great majority (96.5%) of the population. Among females, gravid female accounts for 33.6%, spent female 2.3% .Judging from the sexual maturity stage composition, the maximum spawning for the swarms in this area would occur in late February.

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    BIOCHEMICAL COMPOSITION OF ANTARCTIC KRILL(Euphausia superba Dana)
    1988, 1 (2):  22-27. 
    Abstract ( 1307 )   PDF (508KB) ( 1102 )  

    Biochemical composition of krill Euphausia superba sampled from three stations in Bransfield Strait and norh of king George Island in January 1985 during the First Chinese Antarctic Expedition was analysed. The krill was collected by oblique tow of IKMT, then washed with water and stored immediately at -25℃ in a deep freeze refrigerator. The analysis was carried out later in laboratory. The results are given in Table 1 and 2. Crude protein as a major constituent of the bodies of E. superba ranges from 61 to 70% dry weight (average 66%) . Crude lipid ranges from 5.8 to 16.9% (average 11.5%) . Carbohydrate is the lowest and ranges from 1.4 to 2.0% (average 1.7%) . Ash is 15.6% dry weight in the krill. There is an evidence that negative correlation exists between protein and lipid concentrations in male based on data of different sexual maturity. It seems that there is metabolic conversion from lipid to protein with the development of sexual maturity in male. Analysis of inorganic elements indicates that calcium, sodium, potassium, magnesium and strontium, which are the common elements in seawater, are rather high in the krill bodies. The calcium content is 48 to 56% of total amount of inorganic elements.

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    PRIMARY STUDY ON TEMPERATURE TOLERANCE OF TWO OVERWINTER ZOOPLANKTON SPECIES IN AN ANTARCITC LITTORAL LAKE (BURTON LAKE)
    1988, 1 (2):  28-36. 
    Abstract ( 1508 )   PDF (498KB) ( 969 )  

    Supercooling and thermal tolerance of two overwinter zooplankton species, Drepanopus bispinosus and a calanoida copepod, Cydlppida sp. in an Antarcitc littoral lake-Burton lake, were tested in both seasons. The results show that female adults of D. bispinosus and Cydippida sp. have quite stronger temperature tolerance. The upper thermal 12hrLD50 of female copepod and ctenophore is about 12℃ , and their supercooling 12hrLD50 is -8℃ and -10℃ respectively. The range of their temperature tolerance is wider than that of some other previously reported Antarctic marine invertebrates. The ability of animals in temperature tolerance evidently presented seasonal variation, and it suggests that the animals have good physiological regulation for adapting to enviromental temperature change. This may be resulted in naturel acclimatization in the lake.

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    A STUDY OF DIATOMS IN SURFACE SEDIMENTS FROM THE NORTHWESTERN SEA AREA OF ANTARCTIC PENINSULA
    1988, 1 (2):  37-43. 
    Abstract ( 1310 )   PDF (1170KB) ( 996 )  

    Diatoms in 22 surface sediment samples from the northwestern sea area of Antarctic Peninsula are studied. 82 species of diatoms are examined. The maximum abundance of diatoms ( > 50000 / g) were found in both the middle part of the Bransfield Strait and the deep sea area northwest of the South Shetlands. Medium abundance of diatoms (6000-50000 / g) is observed in the samples from the shallow area of Maxwell bay, the southern sea area of Livingston Island and northwestern shore zone of the Antarctic Peninsula. Low content of diatoms ( < 6000/g) was found in shallow sea area of South Shetlands and northern sea area of Parmer Islands. According to their abundance and ecological charcteristics the diatoms can be divided into three assemblages: 1. Thalassiosira antarctica-Charcatia actinochilus-Eucampia Balaustium. 2. Th. antarctica-Nitzschia kerguelensis-Coscinodiscus lentiginosus. 3. Cos. lentiginosus-E. balaustium -Nitzschia kerguelensisi-Schimperilla antarctica. On the basis of comparison of diatoms in the surface sediments with diatoms in the water and hydrodynamic condition as well as dissolution of diatoms, the sedimentation of the diatioms is discussed in this paper.

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    SYNOPTIC ANALYSIS AND FORCASTING OF HEAVY WINDS OVER ANTARCTIC PENINSULA AND NEIGHBOURING AREA
    1988, 1 (2):  44-53. 
    Abstract ( 1601 )   PDF (904KB) ( 1185 )  

    Basing on the fax surface synoptic maps transmitted by Frei Meteorological Center, Antarctica, Chile, and 500hPa isobaric charts of southern hemisphere in the period of January, 1985 to October, 1987, drown by Beijing Meteorological Center, the heavy winds phenomena occurred over the Antarctic Peninsula and neighbouring area are studied. According to the relative locations of polar cyclones, Antarctic continental high and sub-tropical high, the weather situations producing heavy winds over this area are classified into four models: 1.strong polar cyclones; 2.strong sub-tropical high; 3.high centered on the southern America continent; 4.spreading southwardly of su-tropical high. The methoud of frocasting heavy winds in connection with the models over this areas are put forward.

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    THE DIURNAL AND SEASONAL VARIATIONS OF THE AURORAL ABSORPTIONS
    1988, 1 (2):  54-58. 
    Abstract ( 1243 )   PDF (313KB) ( 1170 )  

    Macquarie Island and Davis Station is located at the centre and the edge of auroral oval respectively. The auroral absorptions over these stations freqently occur in the night. Among them most of sudden ionospheric absorption events occur in pre-midnight (MLT) and most of slow ionospheric absorption events occur in post-midnight. The auroral absorptions are related to the solar activity. Energetic particles of solar wind precipitate mainly in the centre of auroral oval near magnetic midnight, then they spread in all directions, mainly in form of westward jet and less in form of eastward jet .The westward jet is weaker and its spreading velocity is slower, but the eastward jet is stronger and the velocity is higher. With the increasing solar activity, especially after large X flare, the westward jet increases and strengthens. Moreover, at higher latitudes, as over the Davis Station, the auroral absorption increases and strengthens in winter. But at the centre of auroral oval, as over the Macquarie Island, there is not such a seasonal effect. It is possible that the auroral oval shifts southerly and hence produces this effect in winter (for Southern Hemisphere) .

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    SHORT-WAVE COMMUNICATION EXERIMENT AT ANTARCTIC GREAT WALL STATION AND XINSIANG, HENAN PROVINCE,AND THE PROBLEM OF PROPAGATION BEARINGS
    1988, 1 (2):  59-65. 
    Abstract ( 1489 )   PDF (611KB) ( 1104 )  

    In the paper first persented are the results of the SW- communication experiment including received signal quality levels in both stations, available time segments in one day and operational frequency bandwidth, which have been obtained in the compaign of experiment taken from Dec.1985 to Mar.1986.A comparison of the communication frequency bandwidth and the calculated MUF have been made.It is found that the upper limit of the operational frequency bandwidth along the short great circle path which crosses the south-polar, region is approximately in accord with the calculated MUF and the other one along the long great circle path which crosses the north- polar region is different from the calculated MUF. Furthermore, in the paper the results of the bearings measurements taken from Jan.to Feb.1986 are presented in detail.The waves propagated along the great circle path are.of major propagation mode between the Antarctic Great Wall Station and Xinciang Station. But there are some non-great-circle path propagations in certain hours. It is proposed that the resultant non-great-circle path propagation is probably due to the wave scatering effects on , the earth's surface. Intense side lobes of antenna and weak ionospheric absorption help to form the non-great-circle path propagation.

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