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Based on radar. penetrating measmements and ana1ysis of sea ice in the Arctic Ocean, The potentia1 of radar wave to measure sea ice thickness and map the morphology of the underside of sea ice is investigated. The results indicate that the radar wave can penetrate Arctic summer sea ice of over 6 meters thick; and the propagation velocity of the radar wave in sea ice is in the range of 0.142 m.ns-1 to 0.154 m.ns-1 The radar images display the roughness and micro-relief variation of sea ice bottom surface. These features are closely related to sea ice types, which show that radar survev mav be used to identifv and classifv ice tvpes. Since radar images can simultaneously display the linear profile features of both the upper surface and the underside of sea ice, we use these images to quantify their actua1 linear length discrepancy. A new length factor is suggested in relation to the actual linear length discrepancy in linear profiles of sea ice, which may be useful in further study of the area difference between the upper surface and bottom surface of sea ice.
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A field work was conducted at Moshiri in Japan. The work included intensive snow pit work, taking snow grain photos, recording snow and air temperatures, as well as measuring snow water content. By treating the snow as a viscous fluid, it is found that the snow compactive viscosity decreases as the density increases, which is opposite to the relation for dry snow. Based on the measurements of snow grain size, it is shown that, similar to the watersaturated snow, the frequency distributions of grain size at different times almost have the same shape. This reveals that the waterunsaturated melting snow holds the same graincoarsening behavior as the watersaturated snow does. It is also shown that the waterunsaturated melting snow coarsens much more slowly than the watersaturated snow. The C value, which is the viscosity when the snow density is zero, is related to the mean grain size and found to decrease with increasing grain size. The decreasing rate of C value increases with decreasing graincoarsening rate.
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GIS is applied in glaciological research along the traverse route from Zhongshan Station to Dome A, one of the key routes in ITASE project, to display, process, manage and analyze the data obtained mainly by the 3rd Chinese Inland Expedition, together wilh Antarctic databases provided by ADD and BEDMAP project. The ways of ADD data merging and clipping, and coordinate projection transformation of field data and BEDMAP data are introduced. Elevation data derived by GPS navigator are corrected using ADD and ArcView's contour interpolation. Sub-ice topography and ice thickness along the route are extracted from BEDMAP database. Slope and aspect data are derived at each positioning station. GIS is a convenient and useful tool for us to record, query and display a variety of data in detail along the traverse route.
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The traverse route from Zhongshan Station to Dome-A is one of the most important expedition routes of ITASE Project. China carried out 3 inland traverses during the 1996/1997, 1997/1998, 1998/1999 austral summer field seasons. The field team reached inland 300 km, 500 km and 1100 km away from Zhongshan Station respectively. Some ice motion stakes were set up, occupied and reoccupied along the route by GPS technology. It showed that the ice along the traverse route flowed with an 8-25 ma-1 velocity to the northwest, the direction of the bottom of Lamhert Glacier Basin. They coincide with the results along the eastern section from LGB59-70 of the LGB route deduced by Australia in beth values and directions. Furthermore, the directions of the horizontal flow are perpendicular to the surface topography contour.The much larger velocity at the point of LT980 with an approximate value of 100 ma-1 was probed. It was caused by a 15 km wide trough on the bed beneath this point.
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A 211 m depth ice core observation was carried out at the top of the Vestfonna Ice Cap in Nordaustlandet, Svalbard, Norway in 1995. Chronology of the ice core was determined by tritium analysis and comparison to the volcanic eruption of Larki; the resulting accumulation rate is 0.34-0.35 m water eq.·yr-1 for the last 400 year. Concentrations of Al, V, Cr, Fe, Cu, Zn, As, Ag, Cd, Pb and U in an ice core have been determined by an inductively coupled plasma mass spectrometry (ICP-MS) with a desolvated micro-concentric nebulizer, which is a recent development and can achieve high sensitivity with low uptake rate of 60 mL/ min. The concentrations of Pb, Cu, and Zn had increased from 1940s declined from 1970s to present. However, the profiles of Pb, Cu, and Zn were different and they seem to be influenced by the difference of sources. Since the ratios between Cu, Pb, and Zn in Svalbard is similar to that in French Alps, the source area of these elements is estimated to be Europe.
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We measured the spatial variability of Cl- , Na+ , SO4- , NO3 and 7Be concentrations in snow cover along the traverse route from S16 to Dome Fuji station in east Dronning Maud Land, Antarctica. The concentrations of Cl- and Na+ at the coast exponentially decreased with distance from the coast up to 200 km inland. Between 200-1000 km inland, the concentrations of Na+ were nearly constant. On the other hand, the concentrations of Cl- increased with distance beyond 750 km inland. Furthermore, the contribution factors between Cl- and Na+ decreased and the Cl- / Na ratio and the nssCl- / Cl- ratio increased toward the interior of the continent. These results indicate that sea salt aerosols are transported from the coastal region toward the inland region of the Antarctic continent, and that a source of Cl- other than sea salt exists in the inland plateau of Antarctica. The concentrations of SO42- , NO3- and 7Be in snow were relatively high in the coastal region and the inland plateau region compared with those in the katabatic-wind region.
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This paper presents a model of isotopic fractionation by freezing under near equilibrium conditions in an open system and uses the model to predict the fractionation curve and slope gradient of δ18O versus δD. The simulation results show that 1) the fractionation curve and slope gradient are determined by lhe ratio of freezing rate to input rate, 2) the isotopic value in the initial stage of freezing is determined by the isotopic value of initial water; 3) in the latter half of freezing in an open system, the isotopic value converges to a certain value determined by that of input water. These rer suits suggest that the shape of the fractionation curve is the method to distinguish whether freezing occurred in a closed or open system. This analysis is applied to an isotopic curve observed in basal ice of Hamna Glacier, SOya drainage, East Antarctica. The isotopic curve indicates formation by regelation in an open system with a ratio of freezing/ input rates of about 10/ 4.
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Snow/ ice stratigraphic profile is one of the traditional and important research fields in glaciology. The profile drawn by hand, however, is a tough job. Using the Object Oriented Programming (OOP) Visual Basic (VB) , we developed a Drawing Software for Snow/ Ice Stratigraphic Profile (DSSISP). This paper introduces the functions, designing process and realizing methods of the drawing software. It presents the key techniques and aspects that should be payee! attention to during the soft?ware development. Moreover, it also proposes the ideas for complete development of this drawing system. Legend database is a key aspect in the software designing. The major functions of the software include the stratigraphic profile drawing, edition and data management, which can help researchers draw the stratigraphic profile (including the scale, stratigraphic figure, text note and legend) quickly in a computer. In addition, the database technique is used to manage drawing data, which makes the figure drawing convenient and efficient. The drawing data is also convenient to be preserved, exchanged, processed and used.
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Cloudy hands are typical stratigraphic structure in deep ice core. Detailed recording of cloudy bands is important for dating of ice core since pair of series cloudy band and clear layer is corresponds to annual layer and it sometimes corresponds to volcanic ash layer. We developed two type scanners, transmitted light method and laser tomograph method for the stratigraphic study. Measurements were carried out for NGRIP deep ice core, which containing many cloudy hands, using the two type scanners and digital camera. We discussed about the possibility of identification of cloudy bands by each method and about advantage and disadvantage of measurements and their results.
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