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Area of Science:

  • Oceanography
  • Geophysics
  • Fluid Dynamics

Background:

  • Ocean dynamics traditionally focuses on pressure gradient force, often neglecting horizontal gravity.
  • Existing models assume horizontal gravity's negligible impact on oceanic motion across various scales.
  • The vertical component of pressure gradient force and gravity is significantly larger than horizontal components.

Purpose of the Study:

  • To investigate the role and significance of horizontal gravity in large-scale ocean dynamics.
  • To introduce a new metric, the non-dimensional C number, to quantify the influence of horizontal gravity.
  • To develop revised ocean dynamic equations incorporating real gravity.

Main Methods:

  • Utilized community datasets of marine geoid height and ocean surface currents.
  • Calculated the non-dimensional C number, defined as the ratio of horizontal gravity to Coriolis force.
  • Derived new large-scale ocean dynamic equations.

Main Results:

  • The global mean C number was found to be approximately 24, indicating a substantial role for horizontal gravity.
  • Horizontal gravity, previously omitted, is shown to be a significant factor in ocean dynamics.
  • New equations were formulated for hydrostatic balance, geostrophic equilibrium, thermal wind, equipotential coordinate system, and vorticity.

Conclusions:

  • Horizontal gravity plays a more critical role in ocean dynamics than previously recognized.
  • The established omission of horizontal gravity in oceanography needs re-evaluation.
  • The presented revised equations offer a more comprehensive framework for understanding large-scale ocean dynamics.