"waves beneath the sea" phenomenon physics field experiment teaching aspects

"Waves beneath the Sea"

Phenomenon

Physics

Field Experiment

Teaching Aspects

Dan KelleyOceanography Dept.Dalhousie University

http://www.phys.ocean.dal.ca/~kelley/papers/

presentations/2001/AST

"Dead" water

Boat slows to a crawl...

... surfing internal wake

Nansen observation 189x

Ekman explanation 1904

External and Internal Waves: restoring forces

External waves: gravity g

Internal waves: reduced gravity g=gDr/r

0

Physics of Waves

Restoring force ...

... key to all oscillators!

Class Experiment [1]

Class Experiment [2]

Internal Waves in Atmosphere [1]

Wave crests ...

rising air ...

condensation...

... clouds.

Internal Waves in Atmosphere [2]

Banded Surface Slicks

Convergent zones over troughs

Sweeps oil into lines

Visible by eye, radar, satellite, etc.

Ocean from Airplane

Ocean from Space

Ship Radar

Internal waves yield banded slicks...

... banded roughness...

... surface signature of internal waves

SurfaceTidal Bore

Physics of (Tidal) Bore

Other Surface Bores [1]

Other Surface Bores [2]

Peter Galbraith

PhD at Dalhousie

Mixing, internal waves, estuarine physics

Works at DFO in Quebec

Internal Tidal Waves

Chopper - a new type of ship!

Daniel Bourgault

PhD at McGill

Estuarine physics, ocean modelling, internal waves

Works with me at Dalhousie

St. Lawrence Est. Internal Wave

Modelled Internal Wave

View from Shore

St. Lawrence Estuary

Geometrically Corrected View

Enhanced View

Internal Waves on Rotating Planet

Wave "phase" goes one way...

... wave "energy" goes another!

Important to climate...

Scientific Summary

Ocean/atmosphere has internal as well as external waves

These waves may break ...

... causing ocean mixing ...

... affecting biology,

... affecting chemistry,

... affecting climate...

Teaching Summary

Explains cloud patterns

Explains "dead water"

Illustrates universality of Physics (here, across Ocean & Atmosphere)

Illustrates idea of restoring force

Illustrates resonance