NavList:

Fred H wrote:

"but I believe the rate of sedimentation from a
big river such as the Mississippi, Amazon, Rhine, etc, can be fast
enough to change the tidal frequency in enclosed bays, such as Fundy,
over periods of thousands of years."

 

Yes, there will be changes in small areas. That's very true.

 

And:

"This would be a shorter time scale
than what I envision for the "geological time scale," which I see as
ranging between tens of thousands to tens of millions of years.  Now
whether these changes in tidal frequency in local bays would have a
significant effect on global tides is an additional question."

 

Very little effect.

 

And:

"However, the ice ages would have had a profound, global effect on tidal
modulation of the earth's angular momentum.  The end of the last ice
age was rather sudden, but the onset depended on accumulation of snow
over extended periods, and would have been longer, I expect: imagine
building a mile thick sheet of ice at the rate of 20 inches per year."

 

The global tide pattern would have been roughly the same even with sea level so much lower. The tidal friction would have been lower since the shallows over the continental shelves would not have existed. How much, I don't know...

 

The geophysicists who worry about these matters talk about changes in tidal braking occurring over the very-long geological time scale and that the changes arise from re-arrangements of the continents and ocean basins themselves.