Meteorological project in the polar regions

All Japanese Antarctic stations routinely observe and monitor meteorological conditions. Since MAP (Middle Atmosphere Program) (l982-85), various instruments have been used to analyze atmospheric constituents, radiation, and the dynamics of the stratosphere and mesosphere. These include meteorological sounding rockets, laser radar, and an infrared spectrometer. A five-year program was conducted from l987 to l99l mainly at Syowa Station and in the surrounding sea ice as part of the Antarctic Climate Research (ACR) project. The purpose of this research was to study year-to-year variations of the Antarctic atmosphere and sea-ice-atmosphere interaction. The program consisted of satellite data acquisition (NOAA data from l980 and MOS-1 from l989), observations of clouds and precipitation, observations by several newly established automatic weather stations, and monitoring of minor atmospheric constituents such as CO₂ , CH₄ , ozone, and aerosols. A new Antarctic Atmospheric Chemistry project was started in l992 in connection with the International Global Atmospheric Chemistry (IGAC) Program. The project consisted of several coordinated observations of greenhouse gases, tropospheric aerosols and stratospheric ozone and associated components. Stress is laid on the production, decay and transport of minor constituents from lower to higher latitudes, and from the stratosphere to the troposphere and snow surface. Atmospheric minor constituents and aerosols were observed at Dome Fuji Station in l997. Also, observations of greenhouse gases, aerosols and clouds have been started at Ny-Ålesund, Svalbard, in cooperation with the Norwegian Polar Institute.

Data analyses and laboratory experiments in the home institute

Cloud climatology in relation to sea ice extent and the radiation budget have been studied using satellite data. In order to estimate precipitation and the microphysical properties of clouds, data obtained by meteorological radars and microwave radiometers have been analyzed.
Investigation of the "ozone hole" from the viewpoint of the dynamic transport of heat, ozone, and other chemical species is undertaken with the data obtained at Syowa Station, Nimbus-7 TOMS data, and Southern Hemisphere gridded meteorological analysis data. Studies of temporal and spatial variations in CO₂ and CH₄ concentrations, the mechanisms of their transport and exchange between air and sea water have been carried out with the data obtained at Syowa Station, on board the icebreaker Shirase, and at the Arctic field laboratory in Svalbard. The dynamics of polar atmospheric disturbances is examined, based on observational and operational data as well as numerical simulations.

The polar cryosphere plays an important role in global climatic change through its water and energy cycles. The present climate decides the development of ice sheets and glaciers in polar regions, where the paleoclimate has been recorded as signals. The glaciological group concentrates on the following subjects to clarify the present and past status of the cryospheric system in polar regions.

lce core studies

lce core studies are conducted to clarify the paleo polar cryosphere in connection with past global climate. Ice cores have been obtained in the Shirase drainage basin, East Antarctica, and in Greenland and Svalbard, in the Arctic. Deep ice core was obtained at Dome Fuji Station, the highest point of the Dronning Maud Land ice sheet, East Antarctica (77°l8'34" S, 39°4l'5l" E, 3,8l0 m a.s.l.), to study past 350k year global climatic changes. This program is the Japanese contribution to the implementation of the "International Geosphere Biosphere Programme (IGBP)".
The group is responsible for the development of deep ice coring systems, one of which was sucessfully used at Dome Fuji Station, as well as core analytical systems. Ice cores from Antarctica and the Arctic are analyzed for stable isotopes, chemical and physical properties, gas components, and microparticles that reveal a relationship with past climatological factors.

Mass balance studies

Surface accumulation and ablation processes at the ice sheet surface and ice discharge from the ice sheet to the ocean are studied in the eastern part of Dronning Maud Land, Antarctica. The role of sublimation, condensation and drifting snow on surface mass balance is also evaluated.

lce sheet dynamics

The unstable flow regimes of the Shirase Glacier and its hinterland, the Mizuho Plateau, are studied. From l992, the study area in Dronning Maud Land was extended toward the inland area, Dome Fuji Station, and the measurement of 3D movement of the ice sheet and surface strain, and radio-echo soundings were started.

Snow chemistry

The present climate is affected by snow chemistry in the polar regions. Surface snow samples obtained in both Antarctica and the Arctic are analyzed for major ions, pH, stable oxygen isotopes, and microparticle radio isotopes to clarify transportation and depositional processes from various tropospheric and stratospheric sources onto the polar ice sheet.

Remote sensing of the ice sheet

To study Antarctic ice sheet conditions, satellite and airborne remote sensing techniques have been adopted. Satellite data from NOAA, ERS and so on are received at Syowa Station and used for the study of the movement, discharge and surface features of the ice sheet.

Southern Ocean processes
(S. Ushio, H. Ito, S. Aoki, M. Fukuchi, T. Odate)

Because of the sparseness of in-situ data in the Indian Ocean sector, the physical processes of the oceanic structure and circulation system are not yet fully understood. The track of the icebreaker Shirase corresponds to the Indian sector, and she sails every year during the austral summer. To clarify the characteristics of the ocean current fields, drifting ARGOS buoys and subsurface floats (ALACE) have been deployed en route to Syowa Station. This observation focuses on the eastern area of the Kerguelen Plateau and the Antarctic Divergence. Long-term mooring observations have been carried out in the area of the Antarctic Circumpolar Current. Based on these current and temperature data, the formation processes of Antarctic Bottom Water are studied. These study regions are of much interest as they reveal the water/heat/salt exchange system in a meridional section. This study is also a part of the "International Antarctic Zone Program (iAnZone)"

Sea ice variations
(S. Ushio, H. Ito, S. Kudoh, S. Aoki, T. Hirawake, G. Hashida)

The concentration and thickness of the sea ice are observed using a VCR system on board the icebreaker. The nature of seasonal ice distribution is regarded as an indicator of Antarctic climate variations. Oceanographic surveys were carried out in the fast ice region around Syowa Station throughout the years and 1998-2000 to detect seasonal variations in the water structure. Also, sea ice growth and melting processes are important factors for understanding the polar climate system. Satellite remote sensing is very useful in telling us about the ice condition over a wide area. Data from NOAA, ERS-1 and JERS-1 satellites are received at Syowa Station.