Synopsis: Motion in the Ocean

A new study suggests only the topmost part of the seafloor is relevant in determining the conversion of tidal energy to wave energy in the ocean.
Synopsis figure
L. Zhang et al., Phys. Rev. Lett (2014)

The Earth’s climate is strongly affected by the ways in which energy moves into, out of, and around the oceans. One important component of energy flow is the conversion of tidal motion—changes in sea levels caused by gravitational effects of the Moon—into internal ocean waves. Such waves directly influence mixing of water from regions with different temperature and salinity, as well as overall circulation. In a paper in Physical Review Letters, Likun Zhang and Harry Swinney at the University of Texas at Austin, present numerical simulations of how tidal flow over seafloor ridges is transformed into wave energy. They find that only the topmost parts of seafloor topography contribute to wave generation, in effect creating a “virtual seafloor.” It is only above it that tidal energy can be converted to wave energy.

The efficiency of tidal-to-wave energy conversion is difficult to calculate owing to the complex structure of the seafloor: When sea levels rise and fall, water moves up and down on top of underwater mountains and ridges; the vertical motion of the sea bounces off the slopes of these topographic features to create sideways oscillations that form a complex structure of internal ocean waves. Zhang and Swinney carried out simulations on both sinusoidal and random seafloor topographies and discovered that, some distance below the peaks of these structures, no conversion takes place. The reason is that wave interference cancels out tidal-to-internal energy conversion below this virtual seafloor. As a result, the authors suggest that future simulations of this important process can be simpler and more accurate because any topography below the virtual seafloor can be ignored. – David Voss


More Announcements »

Subject Areas

Fluid DynamicsGeophysics

Previous Synopsis

Next Synopsis

Quantum Information

A Quantum Microscope at High NOON

Read More »

Related Articles

Synopsis: Twisted Fluid Flows
Fluid Dynamics

Synopsis: Twisted Fluid Flows

Liquids can follow twisted paths when flowing through porous media. Read More »

Synopsis: Cracking Up

Synopsis: Cracking Up

A new model explains why cracks in cooling lava tend to form hexagonal patterns. Read More »

Focus: The Difference Between Round and Square Pipes
Fluid Dynamics

Focus: The Difference Between Round and Square Pipes

Calculations of the motion of particles carried by a fluid flowing through a pipe find a surprising effect of the pipe's shape. Read More »

More Articles