A Fresh Look at Fundy
By “Awake!”correspondent in Canada
MY PREVIOUS visit to the Bay of Fundy was in childhood, but the same first impression remained: one of disbelief. The wharf stood about thirty feet in height but the ship tied to it was high and dry, or, more accurately stated, seated on a sea of mud.
“Who pulled the plug?” I jokingly commented to a fisherman working on his gear. Stifling a look of resignation, he quietly stated: “Tide’s out. It will be back at 2:30 this afternoon.” This was my reintroduction to Fundy, titleholder to the world’s most mammoth tides.
The Bay of Fundy, a spur off the North Atlantic, is located between Canada’s maritime provinces of Nova Scotia and New Brunswick. The inland end, or “head,” is split by a wedge of land into two smaller bays, Minas Basin and Chignecto Bay. It is here that Fundy flexes its muscles tidal in earnest, displaying ranges in the vicinity of fifty feet.
Tides, Their Causes
The tides roll in and the tides roll out: flood tide, then ebb tide. Fundy, as do most Atlantic coastal areas, sees this pattern repeated twice each lunar day, or period of 24 hours and 50 minutes. Day after day this endless cycle continues, as it has since the days of Noah. Why? What causes this predictable pulselike rhythm?
Basically, the answer lies with the law of gravitation. The sun and moon both exert a powerful gravitational pull on the earth and its oceans. The immense distance to the sun makes its force of attraction very much the lesser of the two. Because the distance between earth and these celestial bodies varies from day to day, likewise their forces of attraction vary. Also, because the declination of the moon, north or south of the earth’s equator, is continually altering, this has an effect on the timing of the tides in the various parts of the globe. These fundamentals in no way provide the complete story, however, for scientists can list a multitude of contributing factors, although mainly of a local geographic nature.
But now, why does Fundy experience two sets of high and low tides per lunar day? Remember that the gravitational pull affects both earth and water, but water is affected to a greater extent since it is not rigid. The time of high tide for any fixed location is a certain time interval after the moon’s passing over the meridian for that location, which causes the ocean to be pulled away from the solid earth and results in a “direct” tide on the moon’s side of the earth. But, on the diametrically opposite side of the earth, a buildup of water also occurs. You might say that here the earth is being pulled downward and away from the water, producing an “opposite” tide.
A point to note, however, is that not all coastal areas of the globe share Fundy’s semidiurnal (twice daily) tidal pattern. Although by far the most common type of pattern, scattered places about the earth experience a “diurnal” rhythm of one rise and one fall in a lunar day. The explanation for this is not simple, but, according to oceanographers, it is considered, basically, a result of various tidal forces and local geographic features combining with a canceling effect.
The difference between high and low water is termed the “range” or “amplitude” of the tides. This range is at its maximum during the time of full and new moons. The resulting “spring tides” are due to the fact that the sun and moon are directly in line with the earth, thus producing the greatest combined force of attraction. During the first and last quarters of the moon, the “neap tides,” or tides of lowest range, occur. The reason: the moon has positioned itself 90 degrees away from the sun, resulting in a combined gravitational pull roughly one half that of the lunar force alone. Economy Point, in Minas Basin, has recorded spring tides of close to fifty-three feet, contrasting with neap tides that have a much smaller although still impressive range of almost twenty-four feet.
Occasionally the earth’s pulse really pounds, when a strong wind or gale from the sea reinforces a high tide. Such a “tidal surge” has a terrifying potential for disaster.
Why Fundy’s Tides Are So Outstanding
But why should Fundy’s tides stand head and shoulders above those in other areas of the world? A look at the map provides part of the answer.
Directing water toward Fundy’s funnellike mouth is a giant scoop formed by the curving coastlines of the adjacent states of Maine, New Hampshire and Massachusetts of the United States! As the swell of water enters the Bay of Fundy, a squeezing takes place, due to the constantly narrowing channel and gradual shelving of the bottom. The result: the gentle swell becomes a rushing mountain of water that rams into the head of the Bay. This accounts for the large variations in tidal range throughout the length of the Bay of Fundy. St. Mary’s Bay, near the mouth of Fundy, records a range of about 22 feet, whereas Chignecto Bay and Minas Basin have the monsters with 46- and 53-foot ranges, respectively.
Also contributing to Fundy’s tides is a factor known as resonance. Simply illustrated, if you disturb water in a container, it tends to oscillate or move with a rocking motion, often splashing over the ends. The oceans contain many such natural containers, one of which is the Fundy Basin. Each of these basins has its own period of oscillation, determined by its length and depth. As Fundy’s tides slosh back and forth twice daily (each 12 hours and 25 minutes), its basin length is just slightly short of giving it perfect resonance with the solar and lunar rhythms. This is one of the basic reasons why Fundy’s tides are giants among giants, when they splash against the ends of the Bay.
Tidal Bores
The silence on the wharf was unexpectedly broken by my fisherman acquaintance: “If you want to see the bore, you had better get with it.” I had almost forgotten. The tidal bore was not something to be missed by a visitor to Fundy. In fact, timetables are published for the benefit of those desiring to see this natural phenomenon.
A “bore” results when the powerful, in-rushing tidewaters collide with the flow of a discharging river. Within the confines of the riverbanks there is produced a wall of water that appears to fight its way upstream. It must be noted that not all coastal rivers experience this wonder, but it is usually associated with relatively shallow depths and sudden increases in the gradient of the riverbed.
A number of Fundy’s rivers present this display; some with but a few inches and others with much greater bores. At the city of Moncton, twenty miles inland from Chignecto Bay, tourists stop regularly to view the three- to four-foot bore on the Petitcodiac River. As impressive as they are, however, Fundy’s tidal bores are dwarfed by those of the Fuchun River in China and South America’s Amazon River. On the Amazon, an observer can see an apparent waterfall, a mile in width and up to sixteen feet in height, moving upstream at over thirteen miles per hour. Yes, the earth’s tides are indeed a powerful force with which to contend.
Living with the Tides
For centuries, the pulse of maritime life has been directed by the “clock of the tides.” Movement of fishing fleet, merchantman and naval vessel alike was affected. Nova Scotia shipyards, once among the busiest in the world of sail, lived by the tides. Twentieth-century shipping still does, in Fundy.
The ebb and flow still govern the many fishermen along the Fundy shore. One method utilizing “weirs,” traps comprising high poles strung with nets, actually makes the tide itself do the fishing. When the tide is in, only the tops of the poles are visible above water. As the tide ebbs, the retreating waters leave the fish stranded by the barrier of nets. Promptly at low tide, the fisherman drives his truck or wagon over the mud to the weir and collects his fish. Trying to beat the fisherman to his harvest are the ever-present hordes of hungry sea gulls. There is, however, a more serious reason why no time is to be lost; the now advancing flood is not selective as to what or whom it traps.
Tapping the surging sea as a source of power is nothing new. In England, the city of London had its first water-pumping station powered by a tide-driven waterwheel built into Old London Bridge. A tidal power installation for pumping sewage was still in use in Hamburg, Germany, in 1880. And the tides of Fundy have also been working, powering mills. One such tidal sawmill was evidently still in operation in Maine as late as twenty years ago.
But to develop large-scale power in Fundy was a different story. This century has seen a number of studies as to its feasibility, the most extensive attempt being at Passamaquoddy Bay, straddling the New Brunswick-Maine border. In each case, man did not have what was needed to harness the restless giant. He lacked cooperation, technology and financing.
A Fresh Look at Fundy
Once again Fundy is a focal point of interest. Why this fresh look at Fundy?
Confidence through technical experience has shifted the harnessing of tidal power from the realm of dream to modest reality. International research has been increasing to the point that two tidal plants are such realities. One is a small experimental project in Kislaya Bay, a site 600 miles north of Murmansk in the U.S.S.R. The other is a full-scale power development across France’s Rance River, currently producing 544 million kilowatt-hours of electricity annually. “So it can be done!” say the engineers, now anxious to pit their skills against the giant, Fundy.
Another reason relates to new solutions to a basic problem with tidal power: the fact that energy production peaks depended, until recently, on the natural rhythm of the tides, and hence did not necessarily coincide with the periods that energy was needed. Production of new reversible-flow turbine-generator units and new design concepts to provide energy in more uniform daily amounts have encouraged a fresh look at the practicality of tidal power.
And, now, perhaps the main catalyst turning attention toward Fundy: the energy crisis! Related to this is the growing concern over pollution. Tidal power is essentially “clean” power, without the known major problems of polluting atmosphere, land or water. Further, tidal power is not limited like mineral resources, but is as dependable as the unceasing tides.
So the need for power exists; the energy supply is available; most of the technical problems, although difficult and complex, can now be faced. What prevents Fundy’s tides from more fully benefiting man? Money! Financing such a colossal scheme, with its huge construction cost, coupled with high interest rates and mounting monetary inflation, is an obstacle indeed! In a worldwide system of things in which priorities are largely governed by financial advantage, this may well prove to be the barrier that for the present allows Fundy’s mammoth tides to remain unharnessed.
[Map on page 8]
(For fully formatted text, see publication)
NEW BRUNSWICK
CHIGNECTO BAY
PASSAMAQUODDY BAY
MAINE
N.H.
ATLANTIC OCEAN
BAY OF FUNDY
NOVA SCOTIA
MINAS BASIN
ST. MARY’S BAY