Journal ArticleDOI
Efficient Inverse Modeling of Barotropic Ocean Tides
TLDR
In this paper, a relocatable system for generalized inverse (GI) modeling of barotropic ocean tides is described, where the GI penalty functional is minimized using a representer method, which requires repeated solution of the forward and adjoint linearized shallow water equations.Abstract:
A computationally efficient relocatable system for generalized inverse (GI) modeling of barotropic ocean tides is described. The GI penalty functional is minimized using a representer method, which requires repeated solution of the forward and adjoint linearized shallow water equations (SWEs). To make representer computations efficient, the SWEs are solved in the frequency domain by factoring the coefficient matrix for a finite-difference discretization of the second-order wave equation in elevation. Once this matrix is factored representers can be calculated rapidly. By retaining the first-order SWE system (defined in terms of both elevations and currents) in the definition of the discretized GI penalty functional, complete generality in the choice of dynamical error covariances is retained. This allows rational assumptions about errors in the SWE, with soft momentum balance constraints (e.g., to account for inaccurate parameterization of dissipation), but holds mass conservation constraints. Wh...read more
Citations
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Journal ArticleDOI
Estimating Uncertain Flow and Transport Parameters Using a Sequential Uncertainty Fitting Procedure
TL;DR: In this paper, the authors describe parameter uncertainties using uniform distributions and fit these distributions iteratively within larger absolute intervals such that two criteria are met: (i) bracketing most of the measured data (>90%) within the 95% prediction uncertainty (95PPU) and (ii) obtaining a small ratio (<1) of the average difference between the upper and lower 95PPU and the standard deviation of measured data.
Journal ArticleDOI
New elevation data triple estimates of global vulnerability to sea-level rise and coastal flooding.
Scott Kulp,Benjamin H. Strauss +1 more
TL;DR: A new digital elevation model utilizing neural networks is employed and it is shown that the new DEM more than triples the NASA SRTM-based estimates of current global population occupying land below projected sea levels in 2100, with more than 200 million people could be affected based on RCP4.5 and 2 degC of warming.
Journal ArticleDOI
Volume loss from Antarctic ice shelves is accelerating
TL;DR: Satellite data is presented showing that ice shelves in many regions around the edge of Antarctica are losing mass, which increases concern about how fast sea level might rise as climate continues to warm.
Journal ArticleDOI
The global flood protection savings provided by coral reefs
Michael W. Beck,Inigo J. Losada,Pelayo Menéndez,Borja G. Reguero,Pedro Díaz-Simal,Felipe Atienza Fernández +5 more
TL;DR: The authors show that the annual damages from flooding would double globally without reefs and they quantify where reefs provide the most protection to people and property.
Journal ArticleDOI
Profiling risk and sustainability in coastal deltas of the world
Z. D. Tessler,Charles J. Vörösmarty,Charles J. Vörösmarty,Michael Grossberg,Irina Gladkova,Hannah Aizenman,James P. M. Syvitski,Efi Foufoula-Georgiou +7 more
TL;DR: Changing flood risk due to extreme events is quantified using an integrated set of global environmental, geophysical, and social indicators to assess changes in regional vulnerability.
References
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Journal ArticleDOI
Global Sea Floor Topography from Satellite Altimetry and Ship Depth Soundings
TL;DR: In this paper, a digital bathymetric map of the oceans with a horizontal resolution of 1 to 12 kilometers was derived by combining available depth soundings with high-resolution marine gravity information from the Geosat and ERS-1 spacecraft.
Journal ArticleDOI
Abyssal recipes II: energetics of tidal and wind mixing
Walter Munk,Carl Wunsch +1 more
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.
Journal ArticleDOI
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.