Comment on “The origin of neap–spring tidal cycles” by Erik P. Kvale [Marine Geology 235 (2006) 5–18]

This paper comments on a recent publication by Erik P. Kvale [Marine Geology 235 (2006) 5–18], who underlines the importance of tropically driven neap–spring cycles. Here it is stressed that tropically driven neap–spring cycles feature a systematic asymmetry, prevalent in both flow velocity time series and sealevel records, which results from the angular frequency relationship between the K1, O1 and M2 tides. Persisting tidal asymmetry, in turn, can determine ebb or flood dominance and plays a prominent role in the depositional processes relevant for marine geological records. It is further argued that shoreline changes can alter the transitions from semidiurnal to diurnal tidal regimes, especially in narrow straits.