Multibeam data of Chukchi sea in Arctic ocean Swath bathymetry and high-resolution reflection data (~3.5KHz) were collected during the ARA03B cruise. On the sea floating ices were not densely distributed and wind and waves were mild and calm. Because of the relatively good sea condition, we could be able to acquire geophysical data with high signal-to-noise ratio. When the ship was ramming to find a thick multi-year ice for an ice station, however, very noisy data were acquired due to the interference to the transducers by crashed ices. The survey tracks the western part of the Arctic Ocean ranging from Mendeleev Ridge to the Northwind ridge (Fig. 1). Most of the Arctic Ocean is poorly surveyed(Kristoffersen and Mikkelsen, 2003) so that new findings were expected through this cruise. The aim of the geophysical survey is to reveal the subsurface feature and sedimentary structures related to the climate change and geological evolution. For this aim, we focused geophysical survey on the following topics. The topics are: - to map subsurface structure on the unknown area - to characterize ice sheet lineation - to survey the distribution of pockmarks