Friday, December 20, 2013

Water Avalanches.

Water Avalanches
Andre Willers
20 Dec 2013
Tsunami's can occur without tectonic movement . Massive shifts of water along the pycnocline causes large wave action on tsunami scale .

Discussion :
1.An illustrative example : see Appendix A

A large volume of cold , saline water suddenly erupts into the North Atlantic . The Richardson number drops far below 0.25 , then an avalanche of water occurs .
This displaces previous top layers of water and large , deep , high-energy waves occur . Tsunami's .
2.This triggers unstable mud-slides , adding to the mess .

3.The percussion effect on clathrates increases methane burps . The density of top seawater decreases , resulting in a runaway positive feedback reaction as the Richardson number drops even further .
An avalanche of water along the pycnocline , resulting in severe surface waves even in deep ocean .

4.Damping : funnily enough , the pycnocline will dampen the tsunami wave as it nears shore , because the Richardson number will increase from a very low level , causing turbulent mixing . This decreases wave amplitude . Neat .
Very rough surf and good fishing .
5.Also described as Rogue Waves
I always wondered why these monster waves never made it ashore .

6.Just be thankful they dampen out , otherwise coastal regions might become very dangerous .
7.As they were during the end of the last ice age .
See et al .
8.Ice cover .
I can intuit , but not prove that there is critical threshold of ice-cover from the arctic where reverberations between the oceanic pycnocline and the ice pycnocline will result in large mid-ocean tsunami's , with some overspill to land areas . Not really difficult in the North Atlantic , if clathrate burps are ignored . Otherwise , difficult . Experience .

9.Mid-Ocean surfing .
For really large and wild waves , forget coastlines . 300 foot mid-ocean waves are not unusual . See Satellite images . And they don't break quickly . You can surf as long as your knees hold out .

There's always room on the Board.

Appendix A
pycnocline is the cline or layer where the density gradient (ρ⁄∂z) is greatest within a body of water. 
 However, vertical mixing across pycnocline is a regular phenomenon in oceans, and occurs through shear-produced turbulence.[3] Such mixing plays a key role in the transport of nutrients.[4]


Pycnoclines become unstable when their Richardson number drops below 0.25. The Richardson number is a dimensionless number expressing the ratio of potential to kinetic energy. This ratio drops below 0.25 when the shear rate exceeds stratification. This can produce Kelvin-Helmholtz instability, resulting in a turbulence which leads to mixing.[11]

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