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: Capillary Effect in Grains Explained
Soft Matter

Synopsis: Capillary Effect in Grains Explained

Numerical simulations show that a previously observed capillary-like action in vibrating grain systems is due to convective motion of the grains.   Read More »

Synopsis: Drops Act Like Tension “Compasses”
Fluid Dynamics

Synopsis: Drops Act Like Tension “Compasses”

A liquid drop’s shape can be used to detect tension anisotropies in an underlying elastic membrane. Read More »

Focus: Why Sediments Are So Uniform
Fluid Dynamics

Focus: Why Sediments Are So Uniform

A new theory suggests that sedimenting particles of irregular shape will drift horizontally as they fall, a result that may resolve a long-standing puzzle. Read More »

More Articles