Seasonal variability in M2 and M4 tidal constituents and its implications for the coastal residual sediment transport

Abstract

We use an observational data set of tidal gauges in the North Sea to investigate the annual cycle of the M2 and M4 amplitudes and phases. The sea surface elevation amplitude of the M2 can vary by 8-10% and the M4 amplitude by 12-30% over the course of the year, with larger amplitudes in summer. The annual phase variations are in the range of 3-15°. The reason for these variations is the thermal structure of the North Sea: a well-developed thermocline in summer and well-mixed water column during winter. The interaction of the M2 and M4 tides is one of the main drivers of the residual sediment transport. Using an analytical model, the seasonal variability in residual sediment transport is estimated. This transport can vary by 10-50% over the course of the year. These variations are mainly related to the seasonal variability of the M2 and M 4 amplitudes. Key Points Amplitude of the M2 can vary by 8-10% and the M4 amplitude by 12-30% Annual phase variations of M2 and M4 are in the range of 3-15° Residual sediment transport can vary by 10-50% © 2014. American Geophysical Union. All Rights Reserved.