A tidal model for eastern Juan de Fuca Strait and the southern Strait of Georgia

Abstract

A three-dimensional, barotropic, finite element model is used to calculate the tidal flows in eastern Juan de Fuca Strait and the southern Strait of Georgia. The harmonics of eight constituents are computed and compared with those from previous finite difference models and those from historical tide gauge and current meter observations. Root-mean-square differences between observed and calculated sea level amplitudes are within 2.0 cm for all constituents, and the phases are within 4.0 ø for all constituents except K2. Horizontal currents from the model are found to reproduce the observed vertical variations in shear except in regions where stratification effects and internal tides exist. In particular, the model representation of currents at six stations in the Canadian Tide and Current Tables (volume 5) is accurate. The pattern of tidal residual currents has much more detail than previous, coatset resolution models, and numerous eddies are predicted. Computed energy flux fields reveal that over a 29-day period only 38% of the tidal power entering Juan de Fuca Strait is transmitted into the southern Strait of Georgia, and of the 39% entering tIaro Strait, 36% is dissipated within the strait itself. 1. Introduction This paper describes the development and validation of a three-dimensional, barotropic, tidal model for eastern Juan de Fuca Strait and the southern Strait of Georgia (Figures 1 and 2). The tides in this region have been previously simulated by a series of finite difference models ICrcart, 1976, 1978; Crean et al., 1988; Stronach, 1991] whose finest resolution of 2 km was restricted by computer limitations. Although nested models with higher resolutions have been developed for regions such as Howe Sound [Stronach et al., 1993], the complicated coastline and numerous narrow channels through the Gulf (Canadian) and San Juan (American) Islands have had only crude approximations. As a consequence, the smaller-scale details of the tidal (and estuarine) flows in this region are not well modeled [oeeBlond et al., 1994] and are still poorly understood. The primary objective of this model is to provide a better resolution for this region and reproduce some of the smaller-scale tidal details. Given the success of finite element models for other sections of the British Columbia coast [Foreman and Walters, 1990; Foreman et al., 1993], a triangular grid was generated for the region and the harmonic, wave equation, finite element method was used to solve the tidal equations. Such a grid offers more flexibility than traditional finite difference grids by locally reducing numerical errors through provision of a better fit of the actual coastline and/or bathymetric features with elements of an arbitrary size, shape, and orientation (within certain regularity constraints). In particular, with the aid of the TRIGRID computer package [Henry and Walters, 1993] it is relatively easy to locally refine a grid by placing smaller elements in regions where the elevation or velocity field is changing rapidly and higher accuracy i...

Radiational tides at the southeastern coast of the Baltic Sea

“…The analysis of a 38 year long time series at Victoria (southern edge of Vancouver Island) demonstrated that the amplitude of harmonic M 2 at this site varies by approximately 6.5% (37.3 ± 2.4 cm). The maximum amplitudes of M 2 are consistently observed in JulyAugust, while the minimum amplitudes are in Febru ary-March [15]. M. Foreman introduced artificial har monics H 1 and H 2 to take into account the seasonal variability of M 2 and to increase the accuracy of tidal forecasting (such harmonics in the decomposition of the tidal potential are absent [9]) 1 , whose frequencies are related to the M 2 frequency as…”

Distribution and Cycling of Suspended Particles Inferred from Transmissivity in the Strait of Georgia, Haro Strait and Juan de Fuca Strait

“…The solid diamonds represent data, the line a linear regression on the data (r 2 = 0.6; n = 15). Tidal currents were computed with a three-dimensional, barotropic, finite element tidal model, including eight tidal constituents (Foreman et al, 1995).…”

A model study of tidal distributions in the Celtic and Irish Sea regions determined with finite volume and finite element models

“…Some recent applications to tidal problems are given in e.g. Foreman et al (1993Foreman et al ( , 1995, Fortunato et al (1997), Ip et al (1998), Legrand et al (2006Legrand et al ( , 2007, Levasseur (2007), Lynch et al (1993Lynch et al ( , 2004 and Walters (1992). A comparison of the performance of finite difference and finite element models for reproducing the M 2 tide and its higher harmonics in the English Channel was performed by Werner (1995).…”