Variability of subtidal current structure in a fjord estuary: Puget Sound, Washington

Bretschneider, Dale E.; Cannon, G. A.; Holbrook, James R.; Pashinski, David J.

doi:10.1029/jc090ic06p11949

Cited by 27 publications

(19 citation statements)

References 14 publications

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“…2a,b). Flood currents are faster than ebb currents at TTP because of topographic siphoning of the ebb currents through Colvos Passage rather than through the channel where TTP is located (Bretschneider et al 1985). The experiment took place during neap tide; therefore, it is likely that our estimates for form drag are lower than they would be during spring tides.…”

Section: Experiments Detailsmentioning

confidence: 44%

Measurement of Tidal Form Drag Using Seafloor Pressure Sensors

Warner

MacCready

Moum

et al. 2013

Journal of Physical Oceanography

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As currents flow over rough topography, the pressure difference between the up-and downstream sides results in form drag-a force that opposes the flow. Measuring form drag is valuable because it can be used to estimate the loss of energy from currents as they interact with topography. An array of bottom pressure sensors was used to measure the tidal form drag on a sloping ridge in 200 m of water that forms a 1-km headland at the surface in Puget Sound, Washington. The form drag per unit length of the ridge reached 1 3 10 4 N m 21 during peak flood tides. The tidally averaged power removed from the tidal currents by form drag was 0.2 W m 22, which is 30 times larger than power losses to friction. Form drag is best parameterized by a linear wave drag law as opposed to a bluff body drag law because the flow is stratified and both internal waves and eddies are generated on the sloping topography. Maximum turbulent kinetic energy dissipation rates of 5 3 10 25 W kg 21 were measured with a microstructure profiler and are estimated to account for 25%-50% of energy lost from the tides. This study is among the first to measure form drag directly using bottom pressure sensors. The measurement and analysis techniques presented here are suitable for periodically reversing flows because they require the removal of a time-mean signal. The advantage of this technique is that it delivers a continuous record of form drag and is much less ship intensive compared to previous methods for estimation of the bottom pressure field.

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Section: Experiments Detailsmentioning

confidence: 44%

Measurement of Tidal Form Drag Using Seafloor Pressure Sensors

Warner

MacCready

Moum

et al. 2013

Journal of Physical Oceanography

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“…In Puget Sound, winds and net seaward-flowing surface currents interact with river outflow to produce a freshwater lens near the surface (Winter et al 1975;Bretschneider et al 1985). The temporal stability of these lenses and the lower variation in irradiance encountered by cells within the lens allow acclimation of photosynthetic absorption to the local irradiance.…”

Section: Discussionmentioning

confidence: 99%

“…10), and cells in these regions are subject to greater variations in irradiance. Subsurface currents in Puget Sound are correlated with tidal cycle (Bretschneider et al 1985). If tides disrupt density gradients within the water column, then acclimation of a ps : a phy occurs on time scales of Ͻ6 h. This acclimation time is consistent with estimates for the time scales for photoacclimation by Thalassiosira pseudonana of 6-8 h for maximal rates of photosynthesis and 2-6 h for photosynthetic efficiency (Lewis et al 1984a), although time scales for acclimation of a given parameter may vary depending on whether irradiance is increasing or decreasing (Cullen and Lewis 1988).…”

Section: Discussionmentioning

confidence: 99%

The response of photosynthetic absorption coefficients to irradiance in culture and in tidally mixed estuarine waters

Culver

Perry

1999

Limnology & Oceanography

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The accuracy of models for primary production and light propagation depends on correct assignment of absorption to photosynthetic pigments. The phytoplankton absorption coefficient is comprised of two components: photosynthetic and photoprotective absorption coefficients. A method based on the fluorescent excitation of chlorophyll a is used to quantify the photosynthetic absorption coefficient for phytoplankton grown in culture and sampled from Puget Sound, Washington. The difference spectrum between total phytoplankton and photosynthetic absorption should be equivalent to photoprotective absorption. For cultures, the difference spectra exhibit peaks near 460 and 490 nm and broad-band absorption between 400 and 450 nm. However, for field samples an additional pronounced peak is observed around 440 nm, similar in shape to the chlorophyll a Soret peak. If the 440-nm peak were associated with photosystem I chlorophyll a, the photosynthetic absorption coefficient will be underestimated by Ͻ15% for these samples.Variability in both coefficients is predictable as a function of irradiance. The photosynthetic coefficient varies inversely with growth irradiance, and the photoprotective coefficient varies directly with irradiance. This direct relationship with irradiance accounts for much of the variability in the spectral shape of the total phytoplankton absorption coefficient. The ratio of the photosynthetic absorption coefficient to the total phytoplankton absorption coefficient increases as a function of decreasing irradiance for cultures and for field samples collected from stratified regions of the water column. This ratio is a photoadaptive parameter that can serve to integrate physiological response to irradiance and has the potential to provide estimates of mixed layer dynamics.Modeling light propagation through the water column and determining a photon budget for the euphotic zone requires an estimate of the phytoplankton absorption coefficient. The phytoplankton absorption coefficient often is the most variable optical component of the water column. The composition and quantity of the phytoplankton assemblage affect both the spectrum and the magnitude of the absorption coefficient. Phytoplankton adapt the composition and concentration of photosynthetic and nonphotosynthetic pigments in response to variations in irradiance intensity and spectral composition (Yentsch and Yentsch 1979;SooHoo et al. 1986;Mitchell and Kiefer 1988;Johnsen and Sakshaug 1993). The accuracy of photon budgets and of bio-optical models for ocean productivity is improved by the incorporation of spectral information into the irradiance and absorption coefficient measurements (e.g., Bidigare et al. 1987Bidigare et al. , 1992Smith et al. 1989). The accuracy also is improved by 1 Present address: Technology, Planning and Management Corporation,

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“…These two time series are highly correlated (0.98), and this suggests that the cross-channel averaged transport does not contain components corresponding to EOF mode 2 or higher EOF modes. This implies that the computation of transports with the separation depth at 30 m filters out components such as bottom water intrusion (Bretschneider et al, 1985). Also, wind stress may not be uniform over the region.…”

Section: Solution Of Initial Value Problem Applied To Puget Sound 32mentioning

confidence: 98%

“…However, several authors (Cannon and Laird, 1978;Cannon, 1983;Bretschneider etal., 1985) noted that wind has significant effects on sub-tidal circulation. Among them, Bretschneider et al (1985) used empirical orthogonal function (EOF) analysis applied to the along channel currents near Three Tree Point (Line B, Fig. 1 (a)).…”

Section: Introductionmentioning

confidence: 99%

An application of a two-layer model to wind driven sub-tidal currents in Puget Sound

Matsuura

1995

J Oceanogr

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A two layer model of an infinitely long channel, with one end closed, is applied to study the sub-tidal response to wind forcing of Puget Sound. The model uses a linear friction parameterization. Data show that the acceleration of current near the surface responds to the wind event almost instantaneously, however, acceleration tends to start decreasing at later times and eventually changes sign even though the wind blows in one direction throughout. Analysis of the model results show that when the forcing frequency is high, the phase lag between forcing and friction causes this phenomena, and as forcing frequency increases, phase lag between forcing and friction approaches td2. When the forcing frequency is low, phase lag between forcing and friction decreases almost linearly with forcing frequency and at extremely low frequency, they almost balance each other. Analysis of the model results show also that the amplitude of baroclinic pressure gradient increases rapidly as forcing frequency decreases and when the forcing frequency is low, the baroclinic pressure gradient becomes important. Effects of baroclinic pressure gradient propagate as a wave from the boundaries and it takes about one day to take effect at the point where the observations were made.

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Variability of subtidal current structure in a fjord estuary: Puget Sound, Washington

Cited by 27 publications

References 14 publications

Measurement of Tidal Form Drag Using Seafloor Pressure Sensors

Measurement of Tidal Form Drag Using Seafloor Pressure Sensors

The response of photosynthetic absorption coefficients to irradiance in culture and in tidally mixed estuarine waters

An application of a two-layer model to wind driven sub-tidal currents in Puget Sound

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