The impact of sea ice on the periodic currents in the eastern Laptev Sea was evaluated in 19981999 within the framework of the Russian-German project Laptev Sea System 2000. Acoustic Doppler current profiler (ADCP) records from two moorings deployed for one year were analyzed. Ice conditions, as derived from remote sensing and ADCPdata, were shown to significantly affect surface circulation down into the pycnocline layer. With fall freeze-up, the tidal currents shift from a barotropic to a baroclinic regime and are furthermore amplified in the pycnocline. Opening of polynyas induces a return to the initial barotropic mode with surface water dynamics primarily controlled by atmospheric forcing.