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Modelling the global ocean tides: modern insights from FES2004

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TLDR
A review of the state-of-the-art in the field of finite element solutions (FES) atlases can be found in this paper, where the authors introduce the FES2004 tidal atlas and validate the model against in situ and satellite data.
Abstract
During the 1990s, a large number of new tidal atlases were developed, primarily to provide accurate tidal corrections for satellite altimetry applications. During this decade, the French tidal group (FTG), led by C. Le Provost, produced a series of finite element solutions (FES) tidal atlases, among which FES2004 is the latest release, computed from the tidal hydrodynamic equations and data assimilation. The aim of this paper is to review the state of the art of tidal modelling and the progress achieved during this past decade. The first sections summarise the general FTG approach to modelling the global tides. In the following sections, we introduce the FES2004 tidal atlas and validate the model against in situ and satellite data. We demonstrate the higher accuracy of the FES2004 release compared to earlier FES tidal atlases, and we recommend its use in tidal applications. The final section focuses on the new dissipation term added to the equations, which aims to account for the conversion of barotropic energy into internal tidal energy. There is a huge improvement in the hydrodynamic tidal solution and energy budget obtained when this term is taken into account.

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The Multi-GNSS Experiment (MGEX) of the International GNSS Service (IGS) - Achievements, prospects and challenges

TL;DR: The status and tracking capabilities of the IGS monitoring station network are presented and the multi-GNSS products derived from this resource are discussed and the achieved performance is assessed and related to the current level of space segment and user equipment characterization.
Journal ArticleDOI

A geodetic plate motion and Global Strain Rate Model

TL;DR: The Global Strain Rate Model (GSRM v.2.1) as mentioned in this paper is a new global model of plate motions and strain rates in plate boundary zones constrained by horizontal geodetic velocities.
Journal ArticleDOI

Present‐Day Crustal Deformation of Continental China Derived From GPS and Its Tectonic Implications

TL;DR: In this paper, the authors process GPS data from continental China to derive site velocities and find that the deformation field inside the Tibetan plateau and Tien Shan is predominantly continuous and large deformation gradients only exist perpendicular to the Indo-Eurasian relative plate motion and are associated with a few large strike slip faults.
Journal ArticleDOI

Deceleration in the Earth's oblateness

TL;DR: For over three decades, satellite laser ranging (SLR) has recorded the global nature of the long-wavelength mass change within the Earth system as discussed by the authors, and the most recent time series of 30 day SLR-based estimates of Earth's dynamical oblateness, characterized by the gravitational degree-2 zonal spherical harmonic J2, indicates that the longterm variation of J2 appears to be more quadratic than linear in nature.
References
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Journal ArticleDOI

Abyssal recipes II: energetics of tidal and wind mixing

TL;DR: Using the Levitus climatology, the authors showed that 2.1 TW (terawatts) is required to maintain the global abyssal density distribution against 30 Sverdrups of deep water formation.
Journal ArticleDOI

Deformation of the Earth by surface loads

TL;DR: In this article, the static deformation of an elastic half-space by surface pressure is reviewed and a brief mention is made of methods for solving the problem when the medium is plane-strategized, but the major emphasis is on the solution for spherical, radially stratified, gravitating earth models.
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TOPEX/POSEIDON tides estimated using a global inverse model

Abstract: Altimetric data from the TOPEX/POSEIDON mission will be used for studies of global ocean circulation and marine geophysics. However, it is first necessary to remove the ocean tides, which are aliased in the raw data. The tides are constrained by the two distinct types of information: the hydrodynamic equations which the tidal fields of elevations and velocities must satisfy, and direct observational data from tide gauges and satellite altimetry. Here we develop and apply a generalized inverse method, which allows us to combine rationally all of this information into global tidal fields best fitting both the data and the dynamics, in a least squares sense. The resulting inverse solution is a sum of the direct solution to the astronomically forced Laplace tidal equations and a linear combination of the representers for the data functionals. The representer functions (one for each datum) are determined by the dynamical equations, and by our prior estimates of the statistics or errors in these equations. Our major task is a direct numerical calculation of these representers. This task is computationally intensive, but well suited to massively parallel processing. By calculating the representers we reduce the full (infinite dimensional) problem to a relatively low-dimensional problem at the outset, allowing full control over the conditioning and hence the stability of the inverse solution. With the representers calculated we can easily update our model as additional TOPEX/POSEIDON data become available. As an initial illustration we invert harmonic constants from a set of 80 open-ocean tide gauges. We then present a practical scheme for direct inversion of TOPEX/POSEIDON crossover data. We apply this method to 38 cycles of geophysical data records (GDR) data, computing preliminary global estimates of the four principal tidal constituents, M(sub 2), S(sub 2), K(sub 1) and O(sub 1). The inverse solution yields tidal fields which are simultaneously smoother, and in better agreement with altimetric and ground truth data, than previously proposed tidal models. Relative to the 'default' tidal corrections provided with the TOPEX/POSEIDON GDR, the inverse solution reduces crossover difference variances significantly (approximately 20-30%), even though only a small number of free parameters (approximately equal to 1000) are actually fit to the crossover data.
Journal ArticleDOI

Significant dissipation of tidal energy in the deep ocean inferred from satellite altimeter data

TL;DR: Satellite altimeter data from Topex/Poseidon is used to map empirically the tidal energy dissipation and shows that approximately 1012 watts—that is, 1 TW, representing 25–30% of the total dissipation—occurs in the deep ocean, generally near areas of rough topography.
Journal ArticleDOI

Tidal Spectroscopy and Prediction

TL;DR: In this paper, 19 years of hourly tide readings at Honolulu, Hawaii and Newlyn, England are analysed without astronomical prejudice as to what frequencies are present, and what are not, thus allowing for background noise.
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