RETRACTED ARTICLE: A Complete Formula of Ocean Surface Absolute Geostrophic Current

Abstract

A complete formula of ocean Surface Absolute Geostrophic current peter c. chu Absolute geostrophic current at the ocean surface (S) contains three components: (1) absolute geostrophic current at the geoid undulation (N), (2) geostrophic shear (between S and N) due to horizontal gradient of dynamic ocean topography, and (3) geostrophic shear (between S and N) due to horizontal gradient of density. However, only the second component is used to represent the surface absolute geostrophic current in physical oceanography and satellite geodesy. four public datasets are used to calculate each component. Evident difference between the surface absolute geostrophic current and the second component (i.e., geostrophic shear due to horizontal gradient of dynamic ocean topography) was found by the statistical characteristics with the relative root mean square difference of 0.605. It shows that the common practice in physical oceanography and satellite geodesy is not correct. the horizontal gradient of dynamic ocean topography alone cannot be claimed as the surface absolute geostrophic current. Ocean surface absolute geostrophic current (AGC) is the linkage between oceanography and satellite geodesy through dynamic ocean topography D, which is the sea surface height (S) (waves and tides filtered out) relative to the geoid undulation (N), D = S − N. Before satellites coming into practice, the two disciplines (oceanography and geodesy) were almost no connection. The gravity measurements over the ocean were very sparse. The marine geoid undulation N would coincide with the average level of sea surface height if the water were at rest. With such a theoretical hypothesis (no motion at N), it is a common practice in oceanography that the horizontal gradient of S relative to the level of no motion (to be considered as D) represents the AGC at S. At that time, the geodetic community did not use the surface AGC. After satellites coming into practice, S is measured by satellite altimetry (relative to ellipsoid) 1,2 ; N (also relative to ellipsoid) is determined by gravity models with satellite measurements, such as Gravity field and steady-state Ocean Circulation Explorer (GOCE) 3 , Gravity Recovery and Climate Experiment (GRACE) 4 , and combined GOCE-GRACE 5. The mean dynamic ocean topography (MDOT) is obtained through subtracting N from mean S. The MDOT calculated from satellite measurements is different from the classical conception (no motion at N) 6. Now, the two communities have common interest on MDOT through the surface AGC. The oceanographic community uses the satellite determined MDOT to get mean general ocean circulation, i.e., surface AGC. The geodetic community uses the surface AGC to verify the static gravity models. Questions arise: Is water at rest at the given N in the oceans? Does horizontal gradient of MDOT represent the mean surface AGC? To answer these questions, a complete formula of ocean surface AGC is presented on the base of geostrophic and hydrostatic balances. It contains three parts: (1) AGC at N, (2) geostro...

RETRACTED ARTICLE: Ocean dynamic equations with the real gravity

“…(4) and (5) the potential of the real gravity is given by From Eq. (6) the real gravity is represented by The horizontal gravity component at the reference ellipsoid surface (z = 0) is obtained using (7) and (10) 12,13 An approximate 3D gravity field for oceanography. According to Eq.…”

Mesoscale and Wind-Driven Variability in The East Auckland Current

“…These results suggested that volume transport estimated from altimeter measurements should be taken with care when considering the EAuC extending to the bottom 12,15 . Whilst geostrophic velocity estimates have their limitations 17 , they adequately represented long term variability of the upper-half water column on the continental slope (M4) and rise (M5), answering Wunsch's (1997) 18 main question: "given the surface geostrophic velocity as measured by an altimeter, how is the motion to be interpreted as a function of depth?" for the studied region.…”