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The Geoid and Ocean Cieculation
Published in Petr Vaníček, Nikolaos T. Christou, GEOID and Its GEOPHYSICAL INTERPRETATIONS, 2020
R. Steven Nerem, Chester J. Koblinsky
Obviously, there are significant time variations of the dynamic topography which must be considered when attempting to determine the mean dynamic topography. In addition to events such as the El Niño, the dynamic topography has large variations due to the seasonal heating and cooling of the ocean, which can have amplitudes as large as 10 to 15 cm for the western boundary currents. These variations have been detected in the hydrographic data as well as in GEOSAT altimeter data.19,47 These variations are more easily determined than the mean dynamic topography since the time variations of the geoid are small compared to the time variations of the dynamic topography.
Nonlinear Dynamics of the Oceanic Flow
Published in Christos H. Skiadas, Charilaos Skiadas, Handbook of Applications of Chaos Theory, 2017
S.V. Prants, M.V. Budyansky, M.Yu. Uleysky
Dynamic topography refers to the topography of the sea surface related to the dynamics of its own flow. In hydrostatic equilibrium, the surface of the ocean would have no topography, but due to the ocean currents, its maximum dynamic topography is on the order of 2 m and are influenced by ocean circulation, temperature, and salinity. A clockwise rotation (anticyclone) is found around “hills” in the northern hemisphere and “valleys” in the southern hemisphere. Conversely, a counterclockwise rotation (cyclone) is found around “valleys” in the northern hemisphere and “hills” in the southern hemisphere.
Phanerozoic history of the Pilbara region: implications for iron mineralisation
Published in Australian Journal of Earth Sciences, 2022
C. S. Perring, J. M. A. Hronsky, M. Crowe
Geodynamic processes in a relatively stable domain, such as the West Australian Craton, are restricted to long-wavelength, low-amplitude flexure of the craton (Cockbain, 2014; Cope, 1975). Tectonic strain is broadly distributed rather than localised, as is the case in active orogenic belts. There are two mechanisms that can produce this long-wavelength, distributed deformation. The first is referred to as dynamic topography and relates to variations in the buoyancy of the underlying convecting mantle, which typically manifest at the 103 km length scale. When continental plates move across relatively hot and buoyant mantle-upwellings, positive dynamic topography results. A good example is southern Africa, where this process produces a broad uplift, up to about 2000 m elevation (Lithgow-Bertelloni & Silver, 1998). Similarly, when plates move over areas of relatively cold, downwelling mantle, negative dynamic topography results in sag-basin formation and sediment deposition. The second mechanism is a propagating flexural response to orogenic events (such as continental collision) at a distal plate margin. Both mechanisms have affected the West Australian Craton throughout its Phanerozoic history (e.g. Czarnota et al., 2014; Mory, 2017).
Subduction geometry controls on dynamic topography: implications for the Jurassic Surat Basin
Published in Australian Journal of Earth Sciences, 2019
T. Smith, V. Bianchi, F. A. Capitanio
Vertical deviatoric stresses were used to determine the dynamic topography through the assumption of topography-compensated stresses σyy = Δρhg along the top, free-slip boundary, allowing for conversion of vertical stress to changes in mantle thicknesses, and by extension dynamic uplift. Therefore, we estimated the impact of the subduction geometry changes by calculation of the difference in dynamic topography. The role of elasticity in our models is neglected as we only account for dynamic topography, that is the component of the topography sustained by viscous stresses, not elastic stresses. Elastic flexure of the lithosphere might contribute to topography (Kaus & Becker, 2007; Mühlhaus, Olsen-Kettle, Shi, & Moresi, 2014; Waschbusch et al., 2009), however, this has an impact on the wavelength of the flexural perturbation once the sedimentary basin is formed, with no regard to the basin-forming mechanisms.