<p>The Bay of Fundy is shaped like a funnel, which amplifies the tidal magnitude, as the water is &quot;squashed&quot; into the bay. There are several other funnel-shaped bays with a large tidal amplitude around the world, e.g. Bristol Channel in Wales, UK.</p>

CC BY-SA 4.0
2021-06-07T12:28:36.640Z
your answer partially explains why the tides are amplified inside the bay, but doesn't explain why the tidal range is large at the entrance to the bay, so it doesn't address my question.
user2554
CC BY-SA 4.0
2021-06-07T05:31:48.963Z
2021-06-07T05:31:48.963Z
Ingvar Lukas
<p>This question is a continuation of my previous question: <a href="https://earthscience.stackexchange.com/questions/21322/questions-about-the-validity-of-a-certain-model-for-tidal-resonance-at-the-bay-o">Questions about the validity of a certain model for tidal resonance at the Bay of Fundy</a>. I need to answer this question in order to return to my previously posted question and test the validity of the model described there.</p>
<p>As far as i understand, the northeastern part of the Gulf of Maine, also called the Bay of Fundy, is the only resonant part of the whole body of water in the Gulf of Maine (which means its natural period is very close to that of the M2 tide component). Therefore, it's logical to assume that the water level at its entrance is fixed to the Atlantic ocean water level, while the tidal range rises higher and higher as we go more and more into the bay; the water level inside the bay is a standing wave with a fixed end at its entrance and a free end at the coasts of its narrow part (this model is called &quot;<em><strong>open harbour</strong></em>&quot;). This description of the situation seems to fit all discussions of tidal resonance phenomenas that i found up to now.</p>
<p>According to this rational, the tidal range at the bay entrance should be similar to that of other coasts near the Atlantic, which is <span class="math-container">$1-2$$\text{m}$</span>. However, loooking into maps of the tidal range at the bay of fundy, like this one,</p>
<p><a href="https://i.sstatic.net/4l7gw.png" rel="noreferrer"><img src="https://i.sstatic.net/4l7gw.png" alt="enter image description here" /></a></p>
<p>reveals that already at the entrance to the bay, the tidal range is about <span class="math-container">$5-6\text{m}$</span>.</p>
<p>Therefore, my questions are:</p>
<ul>
<li>If the water level at the entrance to the bay of fundy is fixed to the Atlantic ocean water level, why is the tidal range there so large?</li>
<li>What are, and this is a general question, the physical effects that govern the enhancement of tidal waves? and i mean other effects than tidal resonance. Is Green's law (which is often used to explain the wave shoaling of tsunamies and other shallow water waves), which might be applied to tidal waves (as they are shallow water waves), relevant here? and if the answer is yes, than why is it relevant only to the Gulf of Maine and not to other US/Canadian coasts?</li>
</ul>

CC BY-SA 4.0
2021-06-06T15:15:27.777Z
The tide at the entrance to the Bay is not the tide of the North Atlantic. The entire Gulf of Maine is part of the resonance
arkaia
CC BY-SA 4.0
2021-06-07T12:24:27.787Z
@arkaia - thanks for the comment! If the entire Gulf of Maine is part of the resonance, can you recommend a website which gives reliable data on its period of resonance? And can you answer my second on Green's law? Because in wikipedia article on tidal resonance Green's law is mentioned...
user2554
CC BY-SA 4.0
2021-06-07T13:05:14.583Z
I doubt is the main factor. Here are some notes from Garrett: https://gfd.whoi.edu/wp-content/uploads/sites/18/2018/03/lecture04_21354.pdf
arkaia
CC BY-SA 4.0
2021-06-07T13:12:28.977Z
From David Brooks (Texas A&M): "When the tidal wave inside the Gulf ebbs and flows back to the Atlantic to begin another cycle, it arrives at the Northeast Channel and the offing of the banks almost exactly in step with the next Atlantic tidal impulse, which sweeps past the channel entrance at the propitious moment when the waters inside can most easily accept the next inrush. "
arkaia
CC BY-SA 4.0
2021-06-07T13:15:51.260Z
The Northeast Channel is likely the main constraint. https://en.wikipedia.org/wiki/Gulf_of_Maine#/media/File:GulfofMaine2.jpg
arkaia
CC BY-SA 4.0
2021-06-08T12:16:33.213Z
@arkaia - The Gerrett's notes you linked two where very useful. One useful formula which i took from Garrett's notes is the formula for resonance frequency of the "Helmholtz's mass exchange mode": $\omega_0 = \sqrt{\frac{gE}{AL}}$. According to information i found, the marine area $A$ of the bay of fundy is about 16,000 squared kilometers, but where can i find reliable information on the bay's entrance cross sectional area $E$?
user2554
CC BY-SA 4.0
2021-06-08T13:21:02.197Z
Well for a start the funnel shaped land that makes up the bay does not end were you are looking, landforms extend underwater.
John
<oceanography><tides>
Why is the tidal range at the entrance to the bay of fundy so high?
user2554
# Why is the tidal range at the entrance to the bay of fundy so high?

(Asked by: username_0 on 2021-06-06)

This question is a continuation of my previous question: [Questions about the validity of a certain model for tidal resonance at the Bay of Fundy](https://earthscience.stackexchange.com/questions/21322/questions-about-the-validity-of-a-certain-model-for-tidal-resonance-at-the-bay-o). I need to answer this question in order to return to my previously posted question and test the validity of the model described there.

As far as i understand, the northeastern part of the Gulf of Maine, also called the Bay of Fundy, is the only resonant part of the whole body of water in the Gulf of Maine (which means its natural period is very close to that of the M2 tide component). Therefore, it's logical to assume that the water level at its entrance is fixed to the Atlantic ocean water level, while the tidal range rises higher and higher as we go more and more into the bay; the water level inside the bay is a standing wave with a fixed end at its entrance and a free end at the coasts of its narrow part (this model is called "***open harbour***"). This description of the situation seems to fit all discussions of tidal resonance phenomenas that i found up to now.

According to this rational, the tidal range at the bay entrance should be similar to that of other coasts near the Atlantic, which is $1-2$$\text{m}$. However, loooking into maps of the tidal range at the bay of fundy, like this one,

[![enter image description here](https://i.sstatic.net/4l7gw.png)](https://i.sstatic.net/4l7gw.png)

reveals that already at the entrance to the bay, the tidal range is about $5-6\text{m}$.

Therefore, my questions are:

* If the water level at the entrance to the bay of fundy is fixed to the Atlantic ocean water level, why is the tidal range there so large?
* What are, and this is a general question, the physical effects that govern the enhancement of tidal waves? and i mean other effects than tidal resonance. Is Green's law (which is often used to explain the wave shoaling of tsunamies and other shallow water waves), which might be applied to tidal waves (as they are shallow water waves), relevant here? and if the answer is yes, than why is it relevant only to the Gulf of Maine and not to other US/Canadian coasts?

**Tags:** oceanography, tides

> **Comments:**
> **username_1**: The tide at the entrance to the Bay is not the tide of the North Atlantic. The entire Gulf of Maine is part of the resonance  
> **username_0**: @username_1 - thanks for the comment! If the entire Gulf of Maine is part of the resonance, can you recommend a website which gives reliable data on its period of resonance? And can you answer my second on Green's law? Because in wikipedia article on tidal resonance Green's law is mentioned...  
> **username_1**: I doubt is the main factor. Here are some notes from Garrett: https://gfd.whoi.edu/wp-content/uploads/sites/18/2018/03/lecture04_21354.pdf  
> **username_1**: From David Brooks (Texas A&M): "When the tidal wave inside the Gulf ebbs and flows back to the Atlantic to begin another cycle, it arrives at the Northeast Channel and the offing of the banks almost exactly in step with the next Atlantic tidal impulse, which sweeps past the channel entrance at the propitious moment when the waters inside can most easily accept the next inrush. "  
> **username_1**: The Northeast Channel is likely the main constraint. https://en.wikipedia.org/wiki/Gulf_of_Maine#/media/File:GulfofMaine2.jpg  
> **username_0**: @username_1 - The Gerrett's notes you linked two where very useful. One useful formula which i took from Garrett's notes is the formula for resonance frequency of the "Helmholtz's mass exchange mode": $\omega_0 = \sqrt{\frac{gE}{AL}}$. According to information i found, the marine area $A$ of the bay of fundy is about 16,000 squared kilometers, but where can i find reliable information on the bay's entrance cross sectional area $E$?  
> **username_2**: Well for a start the funnel shaped land that makes up the bay does not end were you are looking, landforms extend underwater.  

---

## 1 answers

### Answer by username_3 on 2021-06-07. Score: -1

The Bay of Fundy is shaped like a funnel, which amplifies the tidal magnitude, as the water is "squashed" into the bay. There are several other funnel-shaped bays with a large tidal amplitude around the world, e.g. Bristol Channel in Wales, UK.

> **Comments:**
> **username_0**: your answer partially explains why the tides are amplified inside the bay, but doesn't explain why the tidal range is large at the entrance to the bay, so it doesn't address my question.  

---

