Sea ice conditions in Lützow-Holmbukta, Antarctica, have been investigated using ice navigation log from the Japanese icebreaker. Not only basic information such as ice thickness and snow depth, but also ramming icebreaking data are analyzed. The penetrating distances by ramming reflect difficulty for ice navigation and show distinctly interannual variations from 1983 to 2002. Characteristics of the distances variation properly coincide with frequencies of landfast-ice breakup events in the bay.
Antarctic sea ice plays an important role in air-sea interaction and global climate system through energy, water and gas exchange mechanisms. Recently, satellite remote sensing with high spatial/temporal resolutions has been remarkably developed for scientific monitoring. However, we have still much scientific issue on polar sea ice and oceanic processes because of insufficient in-situ data due to limited research cruise in the Antarctic region. Lützow-Holmbukta (Lützow-Holm Bay; LH) is located around 38E in the area off Dronning Maud Land, and the bay is covered with ice almost throughout the year. Japanese Antarctic Research Expeditions (JAREs) have supplied goods (scientific instruments, fuel, provisions, and others) to Syowa (69.0S, 39.5E), which is a continuous wintering station, every austral summer using icebreaker SHIRASE. On her way to the station in the LH, she makes every voyage at nearly the same season and along the same sailing route, which makes the ship a suitable ice-monitoring platform. However, there have not been enough sea-ice data following scientific measurements except for recent observation with video cameras or EMI devices (Uto et al., 2003), therefore it is difficult to estimate sea ice variation quantitatively. Ice navigation of SHIRASE in and around the LH has been recorded in her log since 1983. For example, ice-edge position (in latitude), ice thickness and snow depth on the ice floe are considered as basic information.
