Why is There a Difference in Tides Place to Place?

This is straight from wikipedia: http://en.wikipedia.org/wiki/Tide

The changing tide produced at a given location is the result of the changing positions of the Moon and Sun relative to the Earth coupled with the effects of Earth rotation and the local shape of the sea floor.^[1] Sea level measured by coastal tide gauges may also be strongly affected by wind.

Sun Moon position relative to earth is common for all places on earth. I know the mechanism of tide completely (including why High tide on opposite side of earth too).

Wind has nothing to do with tide level. It may affect only the measurement accuracy of the instrument.

Keeping aside measurement part, we can see great difference in tides place to place. These values are available for any location in Tide Tables for various locations on the earth. These tables give day by day tide level predictions for a place.

From these table books, you can see that at certain locations the tide is not big one and at certain locations it is really great.

As an example

Cochine a port from India has maximum tide of 0.9 metres, as against 8 metres tide at Kandla, another port from India.

Local shape of the sea floor is very general answer. I wish to know, how it affects the tide levels.

Sorry I wasn't able to respond to you earlier, I have been very busy today. I will dig through some of my sailing archive stuff and see if I can find some better references that answer your question.

With regards to wind...you are right, it has no affect on tides. However, it really can have a large impact on top of tide height. Here in San Francisco we have considerable summer wind ...20 -25knots which can push the tide height up quite a bit.

Although a general answer, I think the shape of the local sea floor has a lot more to do with tide height than most people think. Essentially, tidal action is just a cyclic wave pattern. Think about how a wave reacts when it reaches a shoreline. A one meter wave hitting a gradual upslope versus a sharp upslope. Or the same 1 meter wave hitting into a vertical ledge. Each resulting wave is different. I would think local topography would influence tide height just as well.

It would be interesting to look at the topographical differences between the ports you mentioned.

http://www.lhup.edu/~dsimanek/scenario/tides.htm - sorry, link no longer available

http://www.coas.oregonstate.edu/research/po/research/tide/index.html - sorry, link no longer available

Thanks Swi. The links you have sent are great. Those will add to my knowledge greatly.

The wind affects the wave pattern and amplitude, but not the tide amplidude. Wave is overlap of water movement on the tide. Tide is basic rise in water height.

The example you give of 1 meter wave is related to wave and not the tide. If no appreciable wind is there, may be waves will be less, but tide will take place which is rise of water level.

If the topology is too flat the spead of water will be more for the same tide level as against the spread of water at location with sharp gradient. But I do not understand basic reason of different tide amplitudes at different locations.

Think of the bay of fundy with tides of several meters or more.

The funnel shaped opening to the sea collects the water. The momentum of the incoming water is conserved. As the channel narrows, the water is squeezed laterally and expands vertically. The effect is so dramatic that frequently one can observe a tidal bore ... a wave the forms in front of the incoming tide.

To summarize, Conservation of Momentum and Conservation of Energy are the principles involved. As the gravitational energy pulls the tides into the Bay of Fundy, some of its kinetic energy is converted to potential energy in terms of the depth of the water.

Hope this helps.

Good answer by Jcrock

Tide levels are almost entirely due to local geographic differences.

Jcrock talks about the Bay of Fundy, in the UK we have the famouus Severn bore which is quite regular and reliably so, surfers use it for long rides!

Tide heights in the centre of the ocean are very low, although I have no data to hand, as soon as the water nears land the tide is modified considerably and the tide height is modified considerably.

Local heights are very different dependent upon the precise geography but Jcrock's analyis is broadly correct; precise predictions of tide heights are available for many, many, places.

The predictions are based upon the basic geography and the fundamental movements caused by the sun and the moon.

Wind also affects the tide height and can cause a large impact at particular times when a strong wind either pushes, or pulls, a large mass of water. The impact being most effective when the wind creates a surge by continuing in the same direction for a time.

I live by a tidal estuary and see the tide most days and I have a tide clock in my hall.

It should tell me when High and Low tide are but it is not as accurate as I would like it to be. It only takes into account the sun and the moon.

Sleepy

When you guys say that wind has no effect on tidal height, you have to also state the weather conditions. Along the U. S. east and gulf coasts, tidal storm surges can be several meters high, due to storm winds. The winter hurricane of 1978 (date ?) in the Boston area, the tide was high due to lunar/solar attraction, and the storm surge and high winds caused serious ocean/water property destruction along the coast. More recently, the hurricane that ravaged LA and MS coastal areas, etc.

Wind can definitely have an effect on tide height. I live on Lake Erie. At 60 mi NS and 250mi EW (about right), it's too small for tides. A strong wind, however, can raise the level at one end and lower the level at the other end by 2-3 ft.

In addition to the local geography, one must also consider the size of the basin in which the water is "sloshing" back and forth. A most dramatic demonstration of the effect of the size of the basin is here in Panama. In Panama City, on the Pacific side of the isthmus, we have 14-20 foot tides. Sixty miles away, on the Caribbean side of the isthmus, the tides range less than 3 feet. For those of you with limited geographic knowledge, the Caribbean is a bit smaller than the Pacific Ocean...In the "center" of a basin (i.e., Fiji, for the Pacific), one will experience next to no tide at all...