Highest Tides

The Tides

by George Ferguson

The enormous tides of the Bay of Fundy are truly one of the world's great natural wonders.

One hundred billion tonnes of water flows into and out of the Bay on an average tide, twice a day, creating rip-currents, seething up-wellings, swirling whirlpools and a tidal range reaching 16m (53 ft) at the head of the Bay. The volume of water ebbing & flowing is estimated to be 2000 times greater than the daily discharge of the Gulf of St. Lawrence (Thurston, 1994). The immense energy of the tides powers a highly productive, rich and diverse natural ecosystem, in turn shaping the environment, the economy and the culture of the Fundy region.

Tides are considered the heartbeat of the oceans of our planet. They are defined as the response of the oceans to the periodic fluctuations in the cosmic forces of the moon, and the sun, and the perpetual spinning rotation of the Earth (Pinet, 1998). This response is in the form of long, gently-swelling waves that are generated throughout the seas and oceans of the world. These equilibrium tides propagate from place to place and are reflected and dissipated just as other long waves. Thus it is that the tide observed at a particular place is not produced locally, but is the sum of tide waves arriving from all over the ocean, each modified by its experiences along the way. The average tidal range of all oceans around the globe is lm (3 ft).

And further galactic forces come into play. During each phase of a new moon or a full moon, when earth, sun and moon are aligned, higher tides result. These are referred to as "spring tides" a term derived from the springing up of the water. Conversely, twice each month when the sun and moon are at right angles to the earth and opposing each other, the tidal ranges are slighter and are defined as "neap tides" (Pinet, 1998).

The tides along the Atlantic coast are principally semi-diurnal, meaning there are two significant high tides every 24 hours. Along the Nova Scotia Atlantic coast, the tidal range is 1.5m - 2.5m (4 - 8 ft) and the tide arrives and departs at approximately the same time everywhere. However, due to the unique funnel shape and prodigious depth of the Bay of Fundy, the water moves back and forth in sync with the oceanic tides outside. This movement leads to a large increase in the tidal range towards the head of the Bay. Tidal measurements in the Minas Basin are the highest recorded in the world 16m (53 ft).

(Imagine bobbing in a small boat on water that is deeper than a five-story building, and in exactly the same place in less than six hours . . . you can walk on the ocean floor).

And still there are other impelling forces at work in the mighty tides of Fundy. The elementary laws of physics establish that liquid in a basin has a characteristic period of "oscillation" and once set in motion, the liquid will rhythmically slosh back and forth (Cutnell and Johnson, 1995). The speed at which it oscillates depends on the length and depth of the basin. The surface rises first at one end, then at the other, while the level in the middle remains constant. The natural period of oscillation in the Bay of Fundy is approximately 12 hours. And by reason of the contours of the Bay, Fundy's oscillation corresponds with, and is reinforced by, the rhythm of the tides in the Atlantic ocean resulting in "resonance" - the second oscillation induced by the arrival of the ocean tide, of the same speed as the first, resulting in a higher tidal range (Thurston, 1994).

Along the interior Fundy coast, the phenomenal tides have left conspicuous evidence of their power and might: At Hopewell Rocks the tidal currents have carved and sculpted towering statues of red sandstone. Topped by evergreens, they resemble huge flowerpots and stand as one of many Fundy marvels. At St. Martin's, the endless tidal action has carved out spelunkerperfect sea caves. And with each receding tide, vast nutrient-rich mudflats are exposed in the Minas Basin.

The highest- profile phenomenon produced by the tides is the world-famous Reversing Falls at Saint John, where the majestic Saint John River plunges over cascading falls and a narrow passage on its way to the ocean. Twice each day the huge river must yield to the superior power of the Bay. As the tides slowly rise above the level of the river, the falls reverse, and the Saint John river flows upstream (Pinet, 1998).

A similar spectacle occurs at the head of the Bay of Fundy in the form of Tidal Bores. Chignecto Bay and Minas Basin form two arms at the head of the Bay, fed respectively by the Peticodiac River and the Salmon River. At high tide, the extraordinary volume of water in the Bay floods into the rivers. As the river banks narrow, the compressing waters rise in a spectacular surge and a visible standing wave, sometimes lm (3 ft) in height, as the maelstrom of roaring, churning water races upstream at speeds close to 15 km per hour (10 mph). Witnesses have likened the sound to that of an approaching railway train, and first-time viewers are usually struck with awe and fear (Thurston, 1994).

In broad overview, the stupendous Fundy tides are a titanic catalyst to a succession of extraordinary scientific, environmental and ecological wonders. Individually, they are microcosms of the perfectly evolving elements of nature. Collectively, they meld in concert to form a macrocosm considered one of the world's most natural and unspoiled. And underlining the fragility of nature is the certainty that with the continuous passage of time, the surging, monumental tides will ultimately destroy themselves as they slowly erode and disintegrate this unique basin.  

References:

Pinet, P.R. 1998. Invitiation to Oceanogoraphy, web enhanced ed. Jones and Bartlett Publishers. Boston, Ma.

Burzynski, M. and Marceau, A. 1984. Fundy: Bay of the Giant Tides, 3rd ed. The Fundy Guild Publishing, Alma, New Brunswick.

Cutnell, J. D. and Johnson. 1995. Physics, 3rd ed. John Wiley and Sons, Inc. New York

Dolgoff, A. 1998. Physical Geology, Updated version. Houghton Mifflin Co. New York

Randall, D., Burggren, W. and French, K, 1998. Animal Physiology: Mechanisms and Adaptations, 3rd ed. W.H. Freeman and Co. New York.

Smith, R.L. and Smith, T.M. 1998. Elements of Ecology, 4th ed. Benjamin - Cummings Publishing Co. Menlo Park, Ca.

Thurston, H. and Horner, S. 1998. Tidal Life. Nimbus. Toronto.

Relevant Articles

The Geological Formation of the Bay
The Intertidal Zones

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