The Antarctic ice sheet preserves paleoclimate information in the form of physical and chemical stratigraphy. A deep ice core down to 2503 m depth was drilled at Dome Fuji station, East Antarctica, during the 1993-96 Japanese Antarctic Research Expedition inland operations. Oxygen isotope measurements were conducted on 50 cm long samples selected from the entire core length. A palco-temperature profile was obtained for the past 340 ka by assuming the same conversion factors for the past relation as exist today between isotope ratio and both surface temperature and accumulation rate, in the inland region of Dronning Maud Land. The environmental-index profiles such as major chemical and dust contents coincide quite well withVostok ice-core data in general but not in detail. Detailed analysis of these climatic and environmental signals is in progress.

To determine annual layers for reconstructing the past environment at annual resolution from ice cores, we employed snow-stake data back to 1972, tritium content, solid electrical conductivity measurements (ECM) and stratigraphic properties for the 73m ice core at the H72 site, east Dronning Maud Land, Antarctica. the average annual surface mass balance at H72 is 307 mma–1w.e. during the last 27 years from continuous accumulation data, 317 mma–1 w.e. according to the densification model and 311 mma–1 w.e. according to the average surface mass balance for 167 years based on annual-layer counting. the ECM age is closely coincident with tritium age, and corresponds with the snow-stake record back to AD 1972 from the surface to 15 m depth. the H72 ice core is dated as AD 1831by ECMat 73.16 mdepth.The time series of yearly surface mass balance at H72 shows an almost constant 311 mm a–1 w.e. for the last 167 years. the oxygen-isotope records indicate a significant trend to lower values, with negative gradient of 1.7% (100 years)–1.

Densification of firn at the North Greenland Eemian Ice Drilling (NEEM) camp is investigated using density surrogates: dielectric permittivities ∊v and ∊h at microwave frequencies with electrical fields in the vertical and horizontal planes, respectively. Dielectric anisotropy Δ∊ (= ∊v − ∊h) is then examined as a surrogate for the anisotropic geometry of firn. Its size, fluctuations and mutual correlations are investigated in samples taken at depths from the surface to ~90 m. The initial Δ∊ of ~0.06 appears within the uppermost 0.2 m. After that, Δ∊ decreases rapidly until 21–26 m depth. Below this, Δɛ decreases slowly. Layers with more ions of fluorine, chlorine and some cations deposited between the autumn and the subsequent summer deform preferentially during all these stages. This layered deformation is explained partly by the textural effects initially formed by the seasonal variation of metamorphism, and partly by ions such as fluorine, chlorine and ammonium, which are known to modulate dislocation movement in the ice crystal lattice. Insolation-sensitive microstructure appears to be preserved all the way to the pore close-off, within layers of the summer-to-autumn metamorphism. Like previous authors, we hypothesize that calcium is not the active agent in the reported deformation– calcium correlations.

Recently, a 700 m long ice core was drilled at Mizuho Station (2230 m a.s.1.), 270 km south-east of Syowa Station and situated in a typical katabatic-slope region.

In order to obtain basic knowledge for dating the core and for interpreting climatic change and depositional environment change along the core, a study of the regional characteristics of the snow-deposition regime on Mizuho plateau has started. Surface-firn cores 10–30 m deep and snow-stake data obtained along the traverse routes on Mizuho plateau since 1970 were analyzed.

The general trend of annual snow accumulation and the regional characteristics of the δ18O profile of snow cover were obtained.

The amount of acidity in precipitation has been measured in heavy-snowfall regions facing the Sea of Japan. The average pH value of precipitation measured throughout the year at Nagaoka was 4.80 during 4.5 years, 1987–92. During winter the pH value is lower and electric conductivity higher. The spatial distribution of chemical components in new-fallen snow was studied along a 55 km-long sampling route. Results from four surveys showed that acidic snows have average pH values of 4.63–4.90. From the distribution of anion and cation concentration in new-fallen snow, it is concluded that strong northwest monsoons during winter bring an abundance of snow with salt components and many non-salt components from the Sea of Japan and also, possibly, from the Asian continent.

We have investigated two 30 m cores at two different spots in the most heavy snow-accumulation regions on Mizuho Plateau, East Antarctica. Marked seasonal variations periodically appear in oxygen isotope records of the cores. We analyzed one core with no trace of snow melting and found it had a complete record showing a yearly change of annual net snow accumulations from 1920 through 1980. The analysis shows that a yearly variation of annual net accumulation (N.A.) has some relations with that of the annual maximum value (δmax) of δ18O and that of the annual amplitude (Δδ) of the δ18O-change in an annual snow layer. Power spectral analyses with respect to the variation of N.A., δmax and Δδ also indicate that there is commonly a predominant periodicity of about five years.

Characteristics of annual net accumulation were studied in time and space in Mizuho Plateau, Antarctica. Annual variation of net accumulation was obtained from 1914 to 1981 from the analysis of a 30 m core bored in a high accumulation zone. Power spectral analysis of the annual accumulations shows two predominant periodicities, one of 45 years, and the other of 18 years.

Inland, with small accumulation and strong temperature gradient at the surface, developments of depth hoar and the metamorphism of oxygen isotope composition (δ18O) profile of snow take place near the snow surface. From experimental results, the authors propose some models of the metamorphism of δ18O profile of snow with temperature gradient. These models can be divided into two groups: one where a cap, such as an ice crust, is present, and the other without.