Case study on minor tides - modeling, computation or estimation?

Wolfgang Bosch (DGFI, Germany)


Denise Dettmering (DGFI, Germany); Christian Schwatke (DGFI, Germany); Francesca Panzetta (DGFI, Germany)

Event: 2014 Ocean Surface Topography Science Team Meeting

Session: Tides, internal tides and high-frequency processes

Presentation type: Type Poster

In general, global ocean tide models provide tabulated amplitudes and phases for a few most dominant tidal constituents only, namely M2, S2, N2, K2, and K1,O1,P1,Q1. Often, the shallow water tide M4 as well as the long period tides Mf and Mm are also tabulated. The impact of minor tides are accounted for by applying admittance theory, assuming a rather smooth relationship between the tidal height and the amplitude of the tide generated potential within the same species (frequency band). The most recent hydrodynamic finite-element tidal solution FES2012 (Carrère et al. 2012) provides - beside the major tides listed above - quite a number of minor astronomical and compound tides in the diurnal, semi-diurnal and high frequency band. In coastal water some of the minor tides exhibit amplitudes of 5 cm or even higher. On the other hand, satellite altimetry did complete more than two decades with precise monitoring the sea level by two or more contemporaneous missions allowing to estimate and resolve empirically those minor tides with amplitudes above the altimeter noise level.
Thus, there are three alternatives to derive (some) minor tides: by hydrodynamic modeling, by admittance or by empirical estimation. In this study a few shallow water areas are selected to compare some minor tides derived by the three different approaches. We will discuss the differences and address the question if and to what extent modeling and/or estimation contradicts the usual assumption of a linear or quadratic admittance function.
Wolfgang Bosch