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"TIDES"
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Numerical study of baroclinic tides in Luzon Strait
The spatial and temporal variations of baroclinic tides in the Luzon Strait (LS) are investigated using a three-dimensional tide model driven by four principal constituents, O
1
, K
1
, M
2
and S
2
, individually or together with seasonal mean summer or winter stratifications as the initial field. Barotropic tides propagate predominantly westward from the Pacific Ocean, impinge on two prominent north-south running submarine ridges in LS, and generate strong baroclinic tides propagating into both the South China Sea (SCS) and the Pacific Ocean. Strong baroclinic tides, ∼19 GW for diurnal tides and ∼11 GW for semidiurnal tides, are excited on both the east ridge (70%) and the west ridge (30%). The barotropic to baroclinic energy conversion rate reaches 30% for diurnal tides and ∼20% for semidiurnal tides. Diurnal (O
1
and K
1
) and semidiurnal (M
2
) baroclinic tides have a comparable depth-integrated energy flux 10–20 kW m
−1
emanating from the LS into the SCS and the Pacific basin. The spring-neap averaged, meridionally integrated baroclinic tidal energy flux is ∼7 GW into the SCS and ∼6 GW into the Pacific Ocean, representing one of the strongest baroclinic tidal energy flux regimes in the World Ocean. About 18 GW of baroclinic tidal energy, ∼50% of that generated in the LS, is lost locally, which is more than five times that estimated in the vicinity of the Hawaiian ridge. The strong westward-propagating semidiurnal baroclinic tidal energy flux is likely the energy source for the large-amplitude nonlinear internal waves found in the SCS. The baroclinic tidal energy generation, energy fluxes, and energy dissipation rates in the spring tide are about five times those in the neap tide; while there is no significant seasonal variation of energetics, but the propagation speed of baroclinic tide is about 10% faster in summer than in winter. Within the LS, the average turbulence kinetic energy dissipation rate is O(10
−7
) W kg
− 1
and the turbulence diffusivity is O(10
−3
) m
2
s
−1
, a factor of 100 greater than those in the typical open ocean. This strong turbulence mixing induced by the baroclinic tidal energy dissipation exists in the main path of the Kuroshio and is important in mixing the Pacific Ocean, Kuroshio, and the SCS waters.
Journal Article
An introduction to tides
\"This textbook is a self-contained introduction to tides that will be useful for courses on tides in oceans and coastal seas at an advanced undergraduate and postgraduate level, and will also serve as the go-to book for researchers and coastal engineers needing information about tides\"-- Provided by publisher.
Book
Comparison of the tidal signatures in sporadic E and vertical ion convergence rate, using FORMOSAT-3/COSMIC radio occultation observations and GAIA model
Sporadic E or Es is a transient phenomenon where thin layers of enhanced electron density appear in the ionospheric E region (90–120 km altitude). The neutral wind shear caused by atmospheric tides can lead ions to converge vertically at E-region heights and form the Es layer. This research aims to determine the role of atmospheric solar and lunar tides in Es occurrence. For this purpose, radio occultation data of FORMOSAT-3/COSMIC have been used, which provide complete global coverage of Es events. Moreover, GAIA model simulations have been employed to evaluate the vertical ion convergence induced by solar tides. The results show both migrating and non-migrating solar tidal signatures and the semidiurnal migrating lunar tidal signature mainly in low and mid-latitude Es occurrence. The seasonal variation of the migrating solar tidal components of Es is in good agreement with those in the vertical ion convergence derived from GAIA at higher altitudes. Furthermore, some non-migrating components of solar tides, including semidiurnal westward wavenumbers 1 and 3 and diurnal eastward wavenumbers 2 and 3, also significantly affect the Es occurrence rate.
Journal Article
Tides : a very short introduction
The tide is the greatest synchronised movement of matter on our planet. Every drop of seawater takes part in tidal motion, driven by the gravitational pull of the moon and sun. At the coast, we see the tide as a twice-daily rise and fall of sea level that moves the edge of the sea up and down a beach or cliff-face. In some places, the tide is small but at others it can rise in a few hours by the height of a three storey building; it then has to be treated with greatrespect by those who live and work by the sea. 0In this Very Short Introduction David George Bowers and Emyr Martyn Roberts explore what we know about the tides. Blending clear explanations of well known tidal phenomena with recent insights in the deep ocean and coastal seas, Bowers and Roberts use examples from around the world, to tell the story of the tide, considering its nature and causes, its observation and prediction, and unusual tides and their relevance. They explore why tides have attracted the attention of some of the0world's greatest scientists, from the initial challenge of explaining why there are two tides a day when the moon and sun pass overhead just once; a problem that was solved by Isaac Newton. In the 19th century, scientists unravelled the rhythms of the tide; good tidal predictions in the form of tide tables were then possible. The predictions were made on beautiful tide predicting machines constructed of brass and mahogany, some of which can still be seen in maritime museums. In the 20th century, the importance of tides as mixers of sea water became evident. As Bowers and Roberts explore, tidal mixing of the ocean is essential for maintaining its deep circulation, a key part of the climate-control system of our planet. In inshore waters, tidal mixing enhances biological productivity, influences sea temperature and turbidity and creates dramatic features such as maelstroms and tidal bores.
BOOK
A Parameterization of Local and Remote Tidal Mixing
Vertical mixing is often regarded as the Achilles' heel of ocean models. In particular, few models include a comprehensive and energy‐constrained parameterization of mixing by internal ocean tides. Here, we present an energy‐conserving mixing scheme which accounts for the local breaking of high‐mode internal tides and the distant dissipation of low‐mode internal tides. The scheme relies on four static two‐dimensional maps of internal tide dissipation, constructed using mode‐by‐mode Lagrangian tracking of energy beams from sources to sinks. Each map is associated with a distinct dissipative process and a corresponding vertical structure. Applied to an observational climatology of stratification, the scheme produces a global three‐dimensional map of dissipation which compares well with available microstructure observations and with upper‐ocean finestructure mixing estimates. This relative agreement, both in magnitude and spatial structure across ocean basins, suggests that internal tides underpin most of observed dissipation in the ocean interior at the global scale. The proposed parameterization is therefore expected to improve understanding, mapping, and modeling of ocean mixing. Plain Language Summary When tidal ocean currents flow over bumpy seafloor, they generate internal tidal waves. Internal waves are the subsurface analog of surface waves that break on beaches. Like surface waves, internal tidal waves often become unstable and break into turbulence. This turbulence is a primary cause of mixing between stacked ocean layers—a key process regulating ocean currents and biology and a key ingredient of computer models of the global ocean. In this article, a three‐dimensional global map of mixing induced by internal tidal waves is presented. This map incorporates a large variety of energy pathways from the generation of tidal waves to turbulence, accounting for the conservation of energy. The map is compared to available observations of turbulence across the globe and found to reproduce with good fidelity the main patterns identified in observations. This relatively good agreement suggests that internal tidal waves are the main source of turbulence in the subsurface ocean and implies that the map may serve a range of applications. In particular, the three‐dimensional map provides an efficient and realistic means to represent mixing by internal tidal waves in global ocean models. Key Points A global three‐dimensional map of mixing induced by internal tides is presented The map can serve as a comprehensive and energy‐constrained tidal mixing parameterization in global ocean models The map compares well to available microstructure and upper‐ocean finestructure mixing estimates
Journal Article
The toy and the tide pool : a Stuffed bunny science adventure
A fluff-brained bunny named Bear gets lost at the beach where he befriends Princess Shelleena, a mermaid doll, who helps him learn about tides and the fascinating creatures who call tide pools their home.
Book
Interdependence of Internal Tide and Lee Wave Generation at Abyssal Hills: Global Calculations
The generation of internal waves at abyssal hills has been proposed as an important source of bottom-intensified mixing and a sink of geostrophic momentum. Using the theory of Bell, previous authors have calculated either the generation of lee waves by geostrophic flow or the generation of the internal tide by the barotropic tide, but never both together. However, the Bell theory shows that the two are interdependent: that is, the presence of a barotropic tide modifies the generation of lee waves, and the presence of a geostrophic (time mean) flow modifies the generation of the internal tide. Here we extend the theory of Bell to incorporate multiple tidal constituents. Using this extended theory, we recalculate global wave fluxes of energy and momentum using the abyssal-hill spectra, model-derived abyssal ocean stratification and geostrophic flow estimates, and the TPX08 tidal velocities for the eight major constituents. The energy flux into lee waves is suppressed by 13%–19% as a result of the inclusion of tides. The generated wave flux is dominated by the principal lunar semidiurnal tide (M2), and its harmonics and combinations, with the strongest fluxes occurring along midocean ridges. The internal tide generation is strongly asymmetric because of Doppler shifting by the geostrophic abyssal flow, with 55%–63% of the wave energy flux (and stress) directed upstream, against the geostrophic flow. As a consequence, there is a net wave stress associated with generation of the internal tide that reaches magnitudes of 0.01–0.1 N m −2 in the vicinity of midocean ridges.
Journal Article