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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
To introduce the reader to the problem, we briefly mention those oceanographic notions and terms we will be using. A geostrophic current is an oceanic flow in which the pressure gradient force is balanced by the Coriolis effect. Its direction is parallel to the isobars, with the high pressure to the right of the flow in the northern hemisphere, and the high pressure to the left in the southern hemisphere. Geostrophy allows to infer ocean currents from measurements of the sea-surface height by satellite altimeters. The major currents, the Gulf Stream, the Kuroshio Current, the Agulhas Current, and the Antarctic Circumpolar Current, are examples of geostrophic currents.
Oceanographic Factors
Published in Ronald C. Chaney, Marine Geology and Geotechnology of the South China Sea and Taiwan Strait, 2020
When the Coriolis effect and the pressure gradient force are in balance, they are said to be in geostrophic balance. The movement of surface waters around an oceanic gyre is therefore called geostrophic currents. The geostrophic currents are responsible for the circular movement of waters in oceanic gyres and conceivably would serve to maintain the gyres for extended period of time even if the global winds suddenly ceased.
Surface currents in operational oceanography: Key applications, mechanisms, and methods
Published in Journal of Operational Oceanography, 2023
Johannes Röhrs, Graig Sutherland, Gus Jeans, Michael Bedington, Ann Kristin Sperrevik, Knut-Frode Dagestad, Yvonne Gusdal, Cecilie Mauritzen, Andrew Dale, Joseph H. LaCasce
The estimation of geostrophic currents via Sea Surface Height (SSH) from satellite altimeter has a long standing (e.g. Bernstein et al. 1982). To first degree, the SSH is equivalent to the earth's geoid and is highly correlated with seafloor variability. By combining all data collected over several years, models of the static geoid gradually improved (Marsh and Martin 1982). This allowed more accurate determination of the residual: the dynamic variation of the topography which is due to ocean circulation. Thus, under the assumption of geostrophically balanced large-scale currents, the current is inferred from the gradient of sea surface elevation. Le Traon et al. (2015) provides a summary of recent progress and future challenges. Jeans and Lefevre (2008) describe the successful industry application of altimeter-derived currents to quantify variability in Agulhas current impact at particular sites of interest. However they stressed how in situ measurement was critical for reliable quantification of current velocities, even in regions where geostrophic currents are very strong and dominant. In another industry application, Harrington-Missin et al. (2009) explained how altimeter-derived currents can provide valuable quantification of seasonal and interannual trends, complementing deficiencies in relatively short duration in situ measurements.
Seasonal forecasting of winds, waves and currents in the North Pacific
Published in Journal of Operational Oceanography, 2018
The satellite altimeter surface current speed data used are Armor-3D L4 reprocesses satellite altimeter Geostrophic Surface Currents (Guinehut et al. 2012). The data are given on 0.25° for monthly mean values (1993–2015). Altimeter sea height anomalies and mean dynamic topography are provided by the Segment Sol Multimissions d’Altimétrie, d’Orbitographie et de Localisation Précise of the Data Unification and Altimeter Combination (SSALTO/DUACS) to compute surface geostrophic currents. Preliminary analysis has shown surface current speed in Armor-3D to be in reasonable agreement with the drifter data of Lumpkin et al. (2012).