Local diurnal wind‐driven variability and upwelling in a small coastal embayment

Walter, Ryan; Reid, Emma; Davis, Kristen A.; Armenta, Kevin J.; Merhoff, Kevin; Nidzieko, Nicholas J.

doi:10.1002/2016jc012466

Cited by 31 publications

(26 citation statements)

References 51 publications

(95 reference statements)

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“…At the SMB shelf latitude, the diurnal frequency is subinertial (

ω_{K 1} < f

). All three SMB simulations underrepresent the observed diurnal peak in the temperature and velocity spectra, likely due to the lack of diurnal wind‐forcing (sea‐breeze), which has been shown to drive diurnal temperature and velocity variability on the SMB shelf (Cudaback & McPhee‐Shaw, ; Pidgeon & Winant, ; Walter et al, ). Subinertial internal diurnal tidal motions can also be generated by abrupt topography (e.g., Beckenbach & Terrill, ).…”

Section: Methodsmentioning

confidence: 94%

The Effect of Barotropic and Baroclinic Tides on Coastal Stratification and Mixing

2017

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The effects of barotropic and baroclinic tides on subtidal stratification and vertical mixing are examined with high‐resolution, three‐dimensional numerical simulations of the Central Californian coastal upwelling region. A base simulation with realistic atmospheric and regional‐scale boundary forcing but no tides (NT) is compared to two simulations with the addition of predominantly barotropic local tides (LT) and with combined barotropic and remotely generated, baroclinic tides (WT) with ≈ 100 W normalm−1 onshore baroclinic energy flux. During a 10 day period of coastal upwelling when the domain volume‐averaged temperature is similar in all three simulations, LT has little difference in subtidal temperature and stratification compared to NT. In contrast, the addition of remote baroclinic tides (WT) reduces the subtidal continental shelf stratification up to 50% relative to NT. Idealized simulations to isolate barotropic and baroclinic effects demonstrate that within a parameter space of typical U.S. West Coast continental shelf slopes, barotropic tidal currents, incident energy flux, and subtidal stratification, the dissipating baroclinic tide destroys stratification an order of magnitude faster than barotropic tides. In WT, the modeled vertical temperature diffusivity at the top (base) of the bottom (surface) boundary layer is increased up to 20 times relative to NT. Therefore, the width of the inner‐shelf (region of surface and bottom boundary layer overlap) is increased approximately 4 times relative to NT. The change in stratification due to dissipating baroclinic tides is comparable to the magnitude of the observed seasonal cycle of stratification.

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“…At the SMB shelf latitude, the diurnal frequency is subinertial (

ω_{K 1} < f

Section: Methodsmentioning

confidence: 94%

The Effect of Barotropic and Baroclinic Tides on Coastal Stratification and Mixing

2017

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“…However, much larger diurnal cycles in wind speed are found in data from some coastal land stations. These occur due to local sea and land breeze effects, which at locations in the tropics can extend 10s of km from the coast (Miller et al 2003;Gille et al 2005), and can affect many physical and biological processes including the local ocean circulation (e.g., Walter et al 2017) and conceivably sea level to some extent. Inevitably, the sea and land breezes are not represented well in the large-scale meteorological products that are used for storm surge modelling.…”

Section: Daily Coastal Sea Level Variabilitymentioning

confidence: 99%

Forcing Factors Affecting Sea Level Changes at the Coast

et al. 2019

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We review the characteristics of sea level variability at the coast focussing on how it differs from the variability in the nearby deep ocean. Sea level variability occurs on all timescales, with processes at higher frequencies tending to have a larger magnitude at the coast due to resonance and other dynamics. In the case of some processes, such as the tides, the presence of the coast and the shallow waters of the shelves results in the processes being considerably more complex than offshore. However, 'coastal variability' should not always be considered as 'short spatial scale variability' but can be the result of signals transmitted along the coast from 1000s km away. Fortunately, thanks to tide gauges being necessarily located at the coast, many aspects of coastal sea level variability can be claimed to be better understood than those in the deep ocean. Nevertheless, certain aspects of coastal variability remain under-researched, including how changes in some processes (e.g., wave setup, river runoff) may have contributed to the historical mean sea level records obtained from tide gauges which are now used routinely in large-scale climate research.

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“…The HFIW signal observed in the seasonal thermocline is likely associated with forcing by a combination of the local winds and tidal flows within the fjord. HFIWs, with frequencies near the maximum buoyancy frequency, have been observed in lakes (Antenucci & Imberger, ; Boegman et al, ), on continental shelves (Curtin & Mooers, ), in the high‐latitude Arctic (Rippeth et al, ), and in a coastal embayment (Walter et al, ). A variety of processes can generate HFIWs including internal wave‐wave interactions, topographic effects, and shear instabilities.…”

Section: Summary and Discussionmentioning

confidence: 99%

Observations of Shelf Exchange and High‐Frequency Variability in an Alaskan Fjord

2018

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High-frequency observations collected over 3 years are used to describe upper-ocean variability in Behm Canal, a nonglacial fjord in Southeast Alaska. The fjord is sheltered by surrounding topography and connected to the outer continental shelf by a 400-m-deep strait. Summer conditions are characterized by strong near-surface stratification, a sea breeze wind regime, and tidally dominated flows. In nonsummer months, baroclinic subinertial flows exceeding 0.5 m/s dominate the velocity record. The flow events represent a wind-driven response to low-pressure systems that impact the coast as they propagate across the Gulf of Alaska. The observations suggest that the storm systems generate downwelling events that propagate into the fjord with a mode-one-like vertical structure in the upper 60 m. Following the initial up-fjord current pulse lasting approximately a day, a down-fjord flow occurs lasting several days, the duration of the downwelling anomaly. These subinertial downwelling events likely are the dominant mechanism of shelf-fjord exchange, with estimated fjord-flushing times of 50 days. The downwelling events are accompanied by enhanced near-inertial shear, which exhibits downward energy propagation. Evidence for enhanced energy near the maximum buoyancy frequency in the thermocline suggests high-frequency internal wave trapping, with the primary energy source in the semidiurnal band associated with tidal and wind forcing. The observations highlight the importance of shelf-fjord coupling through meteorological forcing and the existence of internal wave energy at a range of frequencies, which have implications for mixing and transport within the fjord.

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Local diurnal wind‐driven variability and upwelling in a small coastal embayment

Cited by 31 publications

References 51 publications

The Effect of Barotropic and Baroclinic Tides on Coastal Stratification and Mixing

The Effect of Barotropic and Baroclinic Tides on Coastal Stratification and Mixing

Forcing Factors Affecting Sea Level Changes at the Coast

Observations of Shelf Exchange and High‐Frequency Variability in an Alaskan Fjord

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