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An approximately 195 mm diameter firn/ice core, 234 m long, was thermally drilled in 1987 austral summer at DE08(66°43'S, 113°12'E) on Law Dome, East Antarctica, where the accumulation rate is about 1200 kg/(m2·a); 10 m ice temperature is about -18.8℃. Analysis was mainly made at the site immediately after drilling. The snow stratigraphy at DE08 is characterised by the lack of coarse-grained snow and other distinct visible feature normally corresponding to annual layers. There is a smooth transformation from fine-grained snow at shallow depth to ice at about 80-90 m which is greater than that at most other polar locations duo to its abnormally high accumulation rate. According to the marked change in the trend of density with depth and in the crystal properties four stages of the transformation of snow to ice and development of crystal structure can be distinguished; settling stage (0-10 m); sintering stage (l0-90 m); rapid crystal growth stage (90-170 m); and dynamic metamorphism stage (170-234 m). The rates of densification and crystal growth from the surface to the depth of the firn-ice transition closely depend on the general temperature. Below the transition zone, the crystal growth rate is higher by a factor of 4.3 in comparison with that at other sites. The very high vertical strain rate at DE08 compared to that at the other sites suggests that the crystal growth rate in the ice layer may increase by the associated deformation.
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Studies on Chinese loess and a comparison with Antarctic ice cores provided a general pattern of global environmental change and the regional differentiation over last 150,000 years. Climatic change revealed by magnetic susceptibility of Linxia loess section in China was paralled with temperature variation revealed by δD of Vostok ice core over last 150,000 years, which indicates a pattern of climatic change tendencies on a long-scale (thousand years). However, the ranges of variation at the same phase, especially, during the last Interglacial age (80,000-140,000 a.B.P.) were more different between Chinese loess sections and Antarctic ice cores.
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From the data of the pitting, geoelectrical prospecting, temperature measurement, salt content analysis and detection by layering frost-heaving instruments, the authors discuss firstly the structural features of sediments in the active layers in this region, and proves the presence of the bowl-shaped frost table in the stone-circles area, and then analyse the regulatities of temperature distribution in the active layer, effect of salt content on electric resistivity, thaw-settlement and frost-heaving, and their control on periglacial land-form development. It suggests that the five layers should exist in the subsurface structure, namely, active layer, frost sand and gravel layer, frost volcanic rock permeated by sea water, frost volcanic rock unpermeated by sea water, and unfrost ancient continental basement. Finally, the permafrost table and its vertical gradient are deduced.
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Based on detailed measurements of density and a numerous data on temperature in shallow boreholes (about 20m deep), the thermal properties and temperature distribution of snow/firn layer on the Law Dome ice cap, Antarctica, are discussed. According to a review of works on thermal properties of snow by
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The population dynamics of
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Fluorine content in bulk sediment and its pore water in Western Antarctic Ocean is 200~395 µg/g and 1.18~1.92 µg/ml respectively, far below the average reported previously in the world oceans (540 µg/g and 2.7 µg/ml, respectively). This study also shows that the distribution of fluorine in the sediments of the area is mainly controlled by the chemical composition of the material from the surrounding islands, and the element seems to be mostly incorporated in the hornblende, thus the correlation between the element and the hornblende amount in the sediments can be expressed statistically as following: F =217 + ln Vh. The low concentration of fluorine in the pore water is largely due to the weak weathering process on the islands and the precipitation of the element with calcium. It can be indicated well by the lower value of anion-exchangeable (HCO3-) F- in the studied area, which is only about one tenth of that in Pacific Ocean and a quarter in South China sea and a half in the sea east of Zhejiang. In addition, the decomposition of the organic matter in the sediment will probabally provide fluorine to the pore water, which can be easily captured by the solid phase. Therefore, the possible mechanism of the element's transition and redistribution in the sedimentary system can be preliminarily described as:
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In this paper, a distribution of the oxygen-minimum layer in the sea area adjacent to the South Shetland Islands and north of the Ardleyd Island, Antarctica, in summer is discussed.The vertical distribution of oxygen in oxygen-minimum layer has the following features: 1). The depth at which the oxygen content greatly decreases is coincident with the depth of pycnocline; 2). There is a thick water layer with low oxygen content; 3). The oxygen-minimum layer occurs below the thermocline and coincides wich the depth at which the temperature mostly increases. According to preliminary result of correlation analysis, the variation of oxygen-minimum layer is related to physical preperties of the circulation and biochemical process in deep layer of the ocean.
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Analysis and study of clastic and clay minerals of surface sediments and their chemical composition in the sea area northwest of the Antarctic Peninsula enable the authors to divide this area basically into four mineralogical provinces: (1)the mineral ogical province of coast and island shelf of the Southern Shetland Islands, (2)the mineral ogical province of the eastern Bransfield Strait, (3)the mineral ogical province of the western Bransfield Strait, and (4)the mineral ogical province of the western Antarctic Peninsula. Finally, the relationships between the mineral distribution and geologic, structure, material sources, glaciers, currents, and environments are briefly described.
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