A 47-yr (1958-2004) model simulation has been analyzed to identify changes of the southern North Sea hydrodynamic regime in the past. A time series analysis revealed time points of changes in volume transports which correspond to recently described changes in the North Sea ecosystem (‘regime shifts’). The strengths of these hydrodynamic changes are shown to vary on a regional scale. Being interested in the analysis of long-term time series (starting in 1962) of hydrophysical and biological parameters measured at the island of Helgoland (54°11.3’ N, 7°54.0’ E, German Bight) we studied seasonal and interannual variations of the North Sea hydrodynamic regime with respect to their effects on the Helgoland area. An Empirical Orthogonal Function (EOF) analysis of spatial patterns of passive tracer Lagrangian transports has been carried out to describe the temporal variability of water mass advection. It could be shown that the southern inflow to the North Sea (via the English Channel) has strengthened since the end of the 70s and that the degree of its impact in the Helgoland area has changed. These regional effects of large-scale hydro-meteorological changes are also discussed in terms of its connection with variations of the NAO index.