Sea ice surveys are conducted along the Okhotsk Sea coast of Hokkaido, Japan using a bottom-mounted IPS and ADCP. This paper reports on the analysis of a 180km long "ice draft profile" of deformed pack ice moving past the mooring site in 2001. The maximum draft during the observation period was 3.6 m. Although the ice draft profile as a wave profile has non-stationary characteristics, the normalized power spectrums of the profile in locally stationary span were roughly the same and the peak wavelength was approximately 100 m. In addition, simulation methods for deformed sea ice draft depth and plane unevenness of sea ice bottom by using one-point measurement data as in this measurement are also discussed.
The Okhotsk Sea coast of Hokkaido is known as the southern limit of sea ice, which forms in high-latitude waters and arrives at Hokkaido between January and March every year. When designing and constructing offshore/coastal structures, pipelines and other underwater and buried structures or winter navigation through pack ice, interaction with sea ice must be fully taken into consideration. It is also necessary to acquire information on the ice draft profile or plane unevenness of ice bottom, ice thickness distribution and pack ice properties in advance for oil spill contingency plans such as prediction of the diffusion range or recovery of oil in ice-infested waters. In particular, with the recent progress of oil and natural gas development along the Sakhalin continental shelf, transport of oil and natural gas to Japan by pipelines and vessels as well as accompanying oil spills or other accidents are expected in the future. Increased understanding of ice conditions in Okhotsk Sea coast of Hokkaido and other engineering studies concerning the above issues will therefore be increasingly necessary in the future.