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


Features

More Features »

Announcements

More Announcements »

Subject Areas

Fluid DynamicsGeophysics

Previous Synopsis

Next Synopsis

Quantum Information

A Quantum Microscope at High NOON

Read More »

Related Articles

Synopsis: Acoustic Waves Direct Particles in Microchannels
Fluid Dynamics

Synopsis: Acoustic Waves Direct Particles in Microchannels

Acoustic waves guided by the channels of a microfluidic device can precisely manipulate microscopic particles suspended in the liquid flowing through the device. Read More »

Synopsis: How Hairy Tongues Help Bats Drink Nectar
Fluid Dynamics

Synopsis: How Hairy Tongues Help Bats Drink Nectar

Experiments and theory show that hairs on a bat’s tongue allow the animal to drink 10 times more nectar than it could if its tongue were smooth. Read More »

Synopsis: Eyeing the Storm
Fluid Dynamics

Synopsis: Eyeing the Storm

Numerical simulations of a hurricane-like system have determined the conditions necessary for the formation of a calm “eye” in the center of the storm. Read More »

More Articles