During the RV Polarstern cruise ARK-XXIII-3 in summer of 2008, a nearly 1000 km long seismic transect along 81° N including the Amundsen Basin, Lomonosov Ridge, Makarov Basin, Mendeleev Ridge and Mendeleev Basin was acquired. The objective was to understand the tectonic evolution of the Makarov Basin in relation to the evolution of the ridge system in the Amerasia Basin. The survey set-up included a300 m streamer and a 32 ltr airgun cluster. Because of ice conditions, gaps remained between the profiles.In addition to reflection seismic data with a 300 m streamer, 8 sonobuoys were deployed along the profiles to better resolve the seismic velocities in the sedimentary column. Initial results show high velocities near the surface in the Makarov Basin with values around 2.6 2.9 km/s. The flat-lying well-stratified units are most likely of Cenozoic age. Towards the ridges, the seismic velocities decrease to 2.2 2.4 km/s. The seismic velocities of the acoustic basement vary from >5.0 km/s in the centralbasin (5.5 s TWT) to 4.1 km/s (3.5 4 s TWT) close to the Mendeleev Ridge. The entire transect is dominated by a partly erosional unconformity, which may mark the break-up of the Lomonosov Ridge from the Siberian/Barents shelves. It divides the sediments into a Cenozoic and Mesozoic portion. First results of the data analysis will be shown.