AbstractIncreases in mean tidal range are observed at most tide gauges along the German North Sea coast. This increase is most pronounced since about the 1950s and is superimposed with strong inter-annual and decadal variability. Amplitudes and characteristics of the increases vary among tide gauges but generally, a large-scale increase in mean tidal high water relevant for design of coastal protection is observed. There are a number of local, regional and large-scale processes that, together with their interactions, may potentially account for the observed changes. The objective of this study is to assess potential contributions from regional and large-scale factors using a combination of modelling and statistical approaches and techniques. No process was identified that could solely account for most of the observed changes. Instead, an interplay between large-scale, regional as well as local factors and their interactions appears to be the most likely explanation for the observed changes.