Home
University of Bergen
Geophysical Institute

24 days of kitchen oceanography

Each day a new experiement will be posted here. Reveal what is hidden behind the windows by clicking on the arrows below.

Introduction
Day 1
Day 2
Day 3
Day 4
Day 5
Day 6
Day 7
Day 8
Day 9
Day 10
Day 11
Day 12
Day 13
Day 14
Day 15
Day 16
Day 17
Day 18
Day 19
Day 20
Day 21
Day 22
Day 23
Day 24

Main content

Surface waves and internal waves

Day 6
06.12.2020

Why is the left wave much smaller than the right one?

Overflatebølger og indre bølger
Photo:
Mirjam Glessmer, GFI

Experiment 6:

We fill two bottles: One is filled half with oil, half with water; the other one is only filled half with water. Make sure both bottles are safely closed!

If both bottles are now moved in a similar way, we see that the waves at the interface between oil and water are larger and move slower than those at the interface between air and water. This is because the force bringing the surface back to the horizontal is much stronger at the air-water interface than at the oil-water interface, because the density difference there is much lower. A smaller restoring force means that waves can grow taller, but on the other hand they run slower.

Chapter 6: Surface waves and internal waves

Overflows can happen either continuously as more dense water is formed, or in bursts. At the interface between the dense water that fills the reservoir to threshold level and the less dense water above it, internal waves can form. Waves propagate much slower on this interface than waves on the sea surface do, but otherwise they behave very similarly. When wave crests reach the threshold, dense water is flushed over. Wave troughs lower the level of dense water at the threshold so that little or none of the dense water spills over the ridge.