Abstract:Preliminary results of the analyses on 700 m ice cores retrieved from Mizuho Station, Antarctica, in 1983 and 1984 are presented. The majority of the physical properties, density, grain-size and shape, and total gas content, were measured at the drilling site. Fabrics, microparticle concentration, electrical conductivity, and stable-isotope concentration 6 18 0 were measured in laboratories after the cores had been taken to Japan.In spite of inaccuracy in measuring both density and total gas content in the i… Show more
“…As has been mentioned in the preceding section, there appear to be increasing fluctuations in the number concentration of microparticles at certain depth ranges shown in Figure 1 These depth ranges are compared with δ18O records of the Mizuho ice core (Fujii and Watanabe, 1988, 1992) (Fujii and Watanabe, 1988, 1992). ∆δ18O in Figure 1 is defined as the deviation of δ18O values at every 5 m in the ice core from the smoothed curve of the depth profile as shown in figure 5 of the paper byHigashi and others (1988) This is an index expressing colder (minus value of ∆δ18O) or warmer temperatures (plus value of ∆δ18O) than the average in the Holocene. The curve shown on the righthand side of Figure 1 was obtained by taking the running mean of every five successive values of ∆δ18O for obtaining a long-term trend of climate change.…”
SEM observations of microparticles in ice-core samples retrieved by the Japanese Antarctic Research Expedition in east Dronning Maud Land have been carried out since 1987. Morphology and elemental composition by EDS of many microparticles taken from various depths of the 700 m Mizuho ice core were compared with each other and with those of stratospheric microparticles in NASA Cosmic Dust Catalogs and microparticles hitherto found in deep ice cores retrieved in Antarctica. Number concentrations of microparticles were measured on all samples throughout the 700 m Mizuho ice core. Remarkable fluctuations found in the depth profile of the concentration seem to coincide with cold climates indicated by δ18O of the same core. Compositional analysis of volcanic ash at a depth of 500.7 m in the Mizuho ice core, dated at approximately 6000 years BP, indicates that the ash originated from the South Sandwich Islands.
“…As has been mentioned in the preceding section, there appear to be increasing fluctuations in the number concentration of microparticles at certain depth ranges shown in Figure 1 These depth ranges are compared with δ18O records of the Mizuho ice core (Fujii and Watanabe, 1988, 1992) (Fujii and Watanabe, 1988, 1992). ∆δ18O in Figure 1 is defined as the deviation of δ18O values at every 5 m in the ice core from the smoothed curve of the depth profile as shown in figure 5 of the paper byHigashi and others (1988) This is an index expressing colder (minus value of ∆δ18O) or warmer temperatures (plus value of ∆δ18O) than the average in the Holocene. The curve shown on the righthand side of Figure 1 was obtained by taking the running mean of every five successive values of ∆δ18O for obtaining a long-term trend of climate change.…”
SEM observations of microparticles in ice-core samples retrieved by the Japanese Antarctic Research Expedition in east Dronning Maud Land have been carried out since 1987. Morphology and elemental composition by EDS of many microparticles taken from various depths of the 700 m Mizuho ice core were compared with each other and with those of stratospheric microparticles in NASA Cosmic Dust Catalogs and microparticles hitherto found in deep ice cores retrieved in Antarctica. Number concentrations of microparticles were measured on all samples throughout the 700 m Mizuho ice core. Remarkable fluctuations found in the depth profile of the concentration seem to coincide with cold climates indicated by δ18O of the same core. Compositional analysis of volcanic ash at a depth of 500.7 m in the Mizuho ice core, dated at approximately 6000 years BP, indicates that the ash originated from the South Sandwich Islands.
“… Fig. 5. Vertical profile of total gas content and δ 18 O (Higashi and others, 1988) in the 700 m deep ice core at Mizuho Station. A solid line of total gas content is fitted to the measured data (solid circles and triangles).…”
Section: Relation Between Total Gas Content and Elevation At Pore Clomentioning
A linear relation between total gas content in ice and the elevation of ice formation (i .e. pore close-off) was obtained from seven shallow ice cores in Mizuho Plateau, Antarctica. The derived relation was applied to the vertical profile of total gas content in a 700 m long ice core at Mizuho Station . A general trend of gradual increase in total gas content was observed from 600 to 200 m in depth, from which toward the upper layer it showed a steep increase. After eliminating the effect of down-slope flow of ice around Mizuho Station, it was estimated that the thickness of the ice sheet decreased by about 350 m at maximum during the last 2000 years. This tendency also appears in the S 18 0 profile of the same ice core.
We measured the Raman spectra of Mizuho and Nansen ice
recovered from Antarctica, and Dye-3 ice recovered
from Greenland, to observe the translational lattice vibrations in
polar ice. Since we investigated the effect
of the aging on the ice and the ice temperature on the spectra, we
chose to study the ice from three different
sites. The ages of the ice Ih range from 4.6 to 100 kyr. The
ice temperatures at the depth it was located
range from 231 to 260 K. The results were compared with the
measurements taken of the Vostok ice by
Fukazawa et al. We found that the relative intensity of the peak
at 300 cm-1 increased as the temperature
at
which the ice was kept for a long period increased from 214 to 237 K.
Since this peak is assigned to a
translational lattice vibration traveling along the hydrogen-bonding
network, we conclude that the structure
of the network in the polar ice varies with time at a very slow rate to
attain an equilibrium state that has
never been found on the laboratory time scale.
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