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Tides and Tidal Currents of the Inland Waters of Western Washington

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Tides and Tidal Currents of the Inland Waters of Western Washington NOAA Technical Memorandum ERL PMEL-56 ~ TIDES AND TIDAL CURRENTS OF THE INLAND WATERS OF WESTERN WASHINGTON Harold O. Mofje1d Lawrence H. Larsen School of Oceanography University of Washington Seatt1e t Washington Pacific Marine Environmental Laboratory Seatt1e t Washington June 1984 UNITED STATES NATIONAL OCEANIC AND. Environmental Research DEPARTMENT OF COMMERCE ATMOSPHERIC ADMINISTRATION Laboratories Mall:llll Baldrlg.. John V. Byrne, Vernon E. Derr Slcrlllry Administrator Director NOTICE Mention of a commercial company or product does not constitute an endorsement by NOAA Environmental Research Laboratories. Use for publicity or advertising purposes of information from this publication concerning proprietary products or the tests of such products is not authorized. ii CONTENTS Page Abstract .... 1 1. Introduction 2 2. Tides 4 2.1 Patterns of Tidal Curves 4 2.2 Geographical Distributions 11 3. Tidal Currents .. 23 3.1 Geographical Distributions 25 3.2 Vertical Dependence 31 3.3 Patterns of Tidal Current and Excursion Curves 33 4. Tidal Prisms and Transports 35 5. Small-Scale Tidal Features 38 5.1 Tidal Eddies. 38 5.2 Tidal Fronts . 41 5.3 Internal Waves 42 6. Summary 43 7. Acknowledgments 47 8. References ... 48 iii Figures Page Figure 1. Chart of Puget Sound and the southern Straits of . .. 5 Juan de Fuca-Georgia showing the locations of representative tide stations (Tables 1-3) and representative tidal current stations ST-l and 25 (Tables 4 and 5) for the Strait of Juan de Fuca. Figure 2. Predicted tides at Port Townsend and Seattle .. 6 (Fig. 1) based on the eight tidal constituents in Table 2. Also shown are partial diurnal and semi- diurnal tides at Seattle. The symbols along the time axis refer to positions of the moon: S = extreme southern declination, • = new moon, E = moon on the equator, t> = first quarter, P =moon at perigee, N =extreme northern declination, 0::: full moon, A = moon at apogee, () = last quarter. Figure 3. Empirical cophase lines of the M tide in the . 12 Straits of Juan de Fuca-Georgia ~ased on a dense net of coastal stations. Dashed lines indicate uncertainty in position. The numbers are phase lags in degrees since Greenwich transit. Modified from Parker (1977a). Figure 4. Empirical co-amplitude lines of the M tide in .. .. 13 2 the Straits of Juan de Fuca-Georgia based on a dense net of coastal stations. Dashed lines indicate uncertainty in position. The numbers are amplitudes in meters. Modified from Parker (1977a) . Figure 5. Empirical cophase lines of the tide in the ...• 15 K1 Straits of Juan de Fuca-Georgia oased on a dense net of coastal stations. Dashed lines indicate uncertainty in position. The numbers are phase lags in degrees since Greenwich transit. Modified from Parker (1977a). Figure 6. Empirical co-amplitude lines of the K tide in 16 the Straits of Juan de Fuca-Georgia bAsed on a dense net of coastal stations. Dashed lines indicate uncertainty in position. The numbers are amplitudes in meters. Modified from Parker (1917a) . Figure 7. Distribution in Puget Sound of M phase lag in .. 17 2 degrees relative to Greenwich transit. From harmonic analyses by the United States Coast and Geodetic Survey and the National Survey (obtained from various sources). iv Page Figure 8. Distribution in Puget Sound of M amplitude in 2 18 meters. Sources same as Figure 7. Figure 9. Distribution in Puget Sound of K phase lag in . 19 1 degrees relative to Greenwich transit. Sources same as Figure 7. Figure 10. Distribution in Puget Sound of K amplitude in 20 1 meters. Sources same as Figure 7. Figure 11. Profiles of M amplitude and M Greenwich .... 24 2 2 phase lag along the main axis of Puget Sound, plotted against the phase of a progressive M wave emanating from Shelton at one head of t~e Southern Basin in a manner consistent with Redfield's theory (1950) of tides in long embayments. After Rattray in Department of Oceanography, University of Washington (1954). Figure 12. Near-surface M tidal current ellipses ... 26 2 observed in the Strait of Juan de Fuca and the southern Strait of Georgia. The M 2 current velocity is a vector extending from the center of a given ellipse to the ellipse itself. The position at Greenwich transit of the velocity vector is indicated by the zero. As time progresses the tip of the vector travels around the ellipse in the direction shown by the arrow. The ellipses were obtained by harmonic analyses of 15- or 29-day series of observations. After Parker (1977a). Figure 13. Near-surface M tidal current ellipses ..•.. 27 2 observed in Puget Sound. Descriptions of symbols same as Fig. 12. The ellipses were obtained from several sources: 29-day analyses (Table 4) of observations by Cannon et al. (1979), ellipses supplied by Parker (private communication) obtained from a recent observation program by the National Ocean Survey, ellipses from Parker (1977a) and estimates (dashed lines) from the National Ocean Survey Tide Table (1977). Figure 14. Locations of MESA current stations (Tables 4 28 and 5) in Puget Sound. After Cannon et al. (1979). Figure 15. Vertical profiles of the M (solid circles) 32 2 and K (solid triangles) t1dal currents at 1 seleceed stations (Fig. 14 and Table 4) in Admiralty Inlet and the Main Basin of Puget Sound. (Asterisks indicate equal values v Page for M and K ). Shown are the amplitudes, 2 1 Greenwich phase lags and flood (toward the Southern Basin) direction. Values are from 29-day harmonic analyses of observations by Cannon et al. (1979). Figure 16. Predicted tidal currents (major component) . 34 and excursions at MESA 10 in Admiralty Inlet and MESA 2 in The Narrows (Fig. 14) based on the eight largest constituents observed at these stations. The symbols along the time axis are defined in the caption of Figure 2. 3 M transports (km ) across sections leading to .... 39 Figure 17. 2 tfie eastern Strait of Juan de Fuca defined as the water transported across a given section during the one flood interval of the M tidal 2 cycle. The tidal prism in the eastern Strait of Juan de Fuca is assumed to be negligible. After Parker (1977a). vi Tables Page Table 1. General tidal characteristics 1 at selected tide. 7 stations in the Puget Sound Region (Fig. 1) computed from the harmonic constants in Table 2. Table 2. Tidal harmonic constants for selected tide stations .. 8 in the Strait of Juan de Fuca and Puget Sound. Phase lags GO are relative to Greenwich transit. Values from various sources published by the United States Coast and Geodetic Survey and the National Ocean Survey. Table 3. Ratio of amplitude for the major tidal constituents 9 for selected stations in the Strait of Juan de Fuca and Puget Sound computed from the harmonic constants in Table 2. Table 4. Current harmonic constants at selected stations .. 29 (see Figs. 1 and 14 and Table 5) computed by 29-day harmonic analyses of current observations. Table 5. Tidal characteristics and amplitude ratios for the 30 major components of tidal current constituents at selected stations (see Figs. 1 and 14). Values are derived from current harmonic constants in Table 4. Table 6. Tidal excursions 1 and their Greenwich lag2 for 36 selected current stations (see Figs. 1 and 14) in the Puget Sound region. Values are derived from current harmonic constants in Table 5. Table 7. Tidal prism (volume between mean high water and . 37 mean lower low water) of Puget Sound. Estimates by Rattray in the Department of Oceanography, University of Washington (1954). vii Glossary amplitude maximum of a tidal constituent's tide or tidal current apogee condition when the moon is at its farthest distance from the earth apogean range semidiurnal range at apogee declination a~gular distance north or south of the equator diurnal occuring once a day diurnal age time elapsed from maximum diurnal forcing until the maximum diurnal tides diurnal inequality difference in successive low water - high water ranges on a given day ebb motion toward the entrance to the ocean epoch period of repetition (18.6 years) for long-term variations in the lunar tides equilibrium hypothetical tide that would occur if the ocean tide responded instantly to tidal forcing equinox condition when the sun is directly above the equator flood motion away from the entrance to the ocean fortnightly occuring every two weeks Greenwich phase time (in units of degrees) elapsed from Greenwich transit lag of a tidal constituent until its high water (or maximum flood current) Greenwich transit passage over the Greenwich meridian and phase reference for tidal constituents harmonic analysis method for estimating harmonic constants from time-series based on the sinusoidal nature of the tidal constituents high water temporary maximum in height of the sea surface internal seiche standing internal wave internal wave wave propagating in the interior of the water driven by the interior mass distribution isobath line of constant water depth principal diurnal declinational (luni-solar) tide low water temporary minimum in the height of the sea surface viii lunitidal interval time elapsed from Greenwich transit until high water of the M tidal constituent 2 M 2 principal semidiurnal lunar constituent major amplitude highest strength of a tidal constituent's current mean high water average of the high waters (usually two-occurring each day) over a 19 year period mean higher high averages of the highest waters occurring each day over a water 19 year period mean lower low average of the lowest waters occurring each day over a water 19 year period mean range average vertical displacement
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