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A Complete Formula of Ocean Surface Absolute Geostrophic Current.
1Naval Ocean Analysis and Prediction Laboratory, Department of Oceanography, Naval Postgraduate School, Monterey, USA. pcchu@nps.edu.
Scientific Reports
|January 31, 2020
Summary
The absolute geostrophic current at the ocean surface is not solely determined by the dynamic ocean topography gradient. Current oceanography practices are inaccurate, requiring a reevaluation of surface current calculations.
Area of Science:
- Physical Oceanography
- Satellite Geodesy
- Geophysics
Background:
- The absolute geostrophic current at the ocean surface (S) is conventionally represented by a single component.
- This component is often simplified to the geostrophic shear derived from the horizontal gradient of dynamic ocean topography.
- This simplification overlooks other contributing factors to the surface current.
Purpose of the Study:
- To investigate the accuracy of using only the dynamic ocean topography gradient to represent the absolute geostrophic current at the ocean surface.
- To quantify the difference between the complete absolute geostrophic current and its commonly used approximation.
- To highlight the necessity of considering all components for precise ocean current estimation.
Main Methods:
- Utilized four publicly available datasets to compute the individual components of the absolute geostrophic current.
- Calculated the absolute geostrophic current at the geoid undulation (N).
- Determined the geostrophic shear components arising from dynamic ocean topography and density gradients.
Main Results:
- A significant discrepancy was observed between the calculated absolute geostrophic current (S) and the geostrophic shear due to dynamic ocean topography.
- Statistical analysis revealed a relative root mean square difference of 0.605 between these two measures.
- This indicates that the commonly used approximation is not representative of the true surface current.
Conclusions:
- The common practice in physical oceanography and satellite geodesy of equating the surface absolute geostrophic current with the horizontal gradient of dynamic ocean topography is incorrect.
- The horizontal gradient of dynamic ocean topography alone is insufficient to accurately represent the absolute geostrophic current at the ocean surface.
- Accurate ocean current modeling requires the incorporation of all contributing factors, including density gradients.
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