The Ancient Cliff Face Forest

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The northern half of the Saugeen Peninsula supports the oldest living trees in Canada east of the Rocky mountains, some as old as 1300 years.

At the 2010 Sources of Knowledge Forum, Peter Kelly, a researcher with the Cliff Ecology Research Group at the University of Guelph presented a summary of what the group had learned about this ancient forest of eastern white cedar which clings to the sheer rock face on the eastern side of the Saugeen Peninsula.

It is quite extraordinary that the existence of this primeval forest was not officially known until 1988 when the University of Guelph conducted a number of research studies along the whole length of the Niagara Escarpment. In order to learn more about the forest, in particular, whether it shared some of the characteristics of other ancient forests around the world, another study was conducted at eleven sites including Bears Rump and Halfway Log Dump. The result was that every site found old growth forest and it showed the same characteristics as old growth forest in other, very different habitats in other parts of the world. These were a freedom from widespread human disturbance, a large number of old trees in the forest and a wide distribution of age among the trees. Thus, at Bears Rump and Halfway Log Dump more than 25 per cent of the trees were more than 250 years old.

The study found evidence that the eastern white cedar can live for over a thousand years. One dead specimen was 1,032 years old when it died. In the area of the Grotto, several trees were up to 560 years old but, unlike the ancient trees on the west coast of North America, which grow to a great size, the trees in this old forest are small. That is because, as the study confirmed, the trees grow very slowly. One specimen was found to have added an average of 0.25 grams of new wood each year, making it the slowest growing tree in Canada.  

According to Kelly, the cedars possess “sectored radial architecture whereby specific parts of the stem are connected to specific root clusters within the rock.” When part of the root dies, perhaps due to drought conditions in that part of the rock, it does not affect the whole tree but only the part of the stem to which the root is joined. Water is not distributed evenly throughout rock and its distribution is uneven. Accordingly, some of the tree’s roots may be in drought while others are able to access water. The root dies first and this leads to the death of the stem to which it is connected. A tree was found on Bears Rump Island that had lost part of its original cambial surface (that part of the tree between the bark and the stem which produces new growth) 600 years before the rest of the tree died.

An effort to preserve these ancient trees, called the Niagara Escarpment Ancient Tree Atlas Project, was started in 1998. The intention was to identify where they are so that they could be protected. This project led to the discovery of 124 living cedars along the Escarpment that were more than 500 years old. Ten were over 1000 years old and two of these were over 1300 years old. All were inside the Lions Head Provincial Nature Reserve.

Peter Kelly and Douglas Larson of the University of Guelph have published an illustrated book about the ancient forest on the peninsula called The Last Stand. One of the observations they make is the interesting distribution of eastern white cedar versus that of other native species on the west side of the peninsula. They found that cedar is the most dominant tree on the cliff face but ten metres back from the cliff edge they cease to be dominant and give way to the typical Great Lakes forest such as maple. Those cedars at the transition point show suppressed growth compared with those on the cliff edge.

The study of tree rings is called Dendochronology. The variation in the pattern of tree rings tells a lot about climatic conditions at the time the ring was forming. The results of studying the ancient trees along the escarpment shows that tree growth rates were higher in the 20th century than for any other period in history of this forest. According to Kelly the inevitable conclusion is that we are experiencing an unprecedented period of climate change and that the increased growth rates may spell the end, in the long run, of this ancient forest given that its survival is linked to the ability of the trees to grow slowly.

Dark Skies Revisited

One of the last remaining areas of Southern Ontario to be free of light pollution is the Saugeen Peninsula. The 2011 Sources of Knowledge Forum, Dark Skies, Bright Minds focussed on the importance of the community preserving this feature.

The plenary sessions offered presentations and panel discussions on a wide range of dark sky related topics, including the ecological impacts of light pollution. Several presenters showed how light pollution has serious impacts on birds, bats, fish and many other species.

In August, 2004 the Council proclaimed that the Municipality should be a Dark Sky Community. The Council’s intention was to preserve and protect the night time environment and the dark sky by encouraging the use of appropriate outdoor lighting, raising awareness of the problems of light pollution and to educate residents and visitors about the values of quality outdoor lighting.

Later, the Biosphere Association established the Bayside Astronomy Project in Lions Head. This very successful venture (16,000 people have participated in the program) has run for several years supported by an annual $2000 annual grant from the Council. This year, as the program continues to grow in popularity and now requires an additional student assistant, the Council, in its unfathomable wisdom, has reduced the grant to $1500.

One of the presenters at the SOKF, Terence Dickinson, the Editor of Sky News Magazine has seen night time lighting expand much faster than has the population. By one estimate, it has quadrupled in intensity every decade since 1960, meaning that the global night lighting illumination is 1000 times brighter now than it was 50 years ago. According to a Toronto Star article in 2017, satellite observations during five Octobers show Earth’s artificially lit outdoor area grew by 2 per cent a year from 2012 to 2016. Much of it is waste lighting, flooding uselessly upward and destroying our heritage of nature’s star-filled night.

The National Optical Astronomy Observatory estimates that “poorly aimed and unshielded” outdoor lights waste more than 17 billion kilowatt-hours of energy each year in the U.S.  The U.S. Department of Energy estimates that 13 percent of home electricity usage goes toward outdoor lighting. More than one-third of that light is lost to skyglow — the artificial brightness of the night sky — resulting in about $3 billion wasted per year.

Light at night throws off the biological clocks of nocturnal animals and interferes with their migration patterns. Birds can also become disoriented by lights and may collide with brightly lit towers and buildings.

Less than 100 years ago, everyone could look up and see a spectacular starry night sky. Now, millions of children across the globe cannot experience the Milky Way where they live. In urban centres, only a few hundred of the brightest stars are visible and the Milky Way has disappeared.

As pointed out by one presenter, Robert Dick of the Royal Astronomical Society of Canada: Based on discussions with municipal officials in the 1990s, the chief arguments for the increase of urban outdoor lighting were the perceived need for more light at night to reduce crime and that “everyone” wants more light at night. Suggestions on how to reduce light pollution were dismissed because of the cost of shielded fixtures and the apparent lack of public concern over glare and light trespass.

According to the 2016, World Atlas of Artificial Night Sky Brightness 80 per cent of the world’s population lives under skyglow. In the United States and Europe 99 per cent of the public cannot experience a natural night. The physicist Lawrence Krauss recalled that when showing a slide of the Milky Way to his university class in Cleveland he felt bound to point out to the students that what they were looking at were stars.

For even the mildly curious, the magic of the night sky cannot be overstated. When we look up on a clear night we are observing an environment that is unimaginably cold (at close to absolute zero) sprinkled with objects that are at the extremes of hotness. In spite of its apparently slow moving or static state, all of the stars we see are moving at hundreds of thousands of kilometres per second – a perfect demonstration of the Theory of Relativity.

Observing the night sky has enabled humanity to confront the most challenging of life’s conundrums, that the earth is not flat, that it is not the centre of the universe, and that we are indeed staggeringly insignificant. We have calculated the age of the universe with precision and we know what happened within the first billionth of a second. We know that the universe almost certainly arose from a quantum mechanical fluctuation and not through divine intervention and we know that we, ourselves, are made from elements that were created in the centre of stars and blown out into space in stellar explosions millions of years ago.

When we look out into space we are looking back into time because the light from the stars has taken millions of years to reach the Earth. But we are also looking at infinity because we know that the universe is expanding endlessly. To deprive our children of the same intellectual joy and wonder that we and our forebears benefited from, merely for the sake of advertising, or because of an irrational fondness for illumination and a fear of the dark, or from a misinformed notion that crime is less likely to occur in the light, is sad indeed.

While, most businesses, churches and individuals have cooperated with the Municipality’s Dark Skies initiative by installing outdoor lighting that shines down rather than skywards, regrettably, there are still a few area businesses and at least one church that still insist on putting their own interests ahead of the fundamental right of all people, especially young people, to experience one of nature’s greatest spectacles.

Local astronomer, Doug Cunningham captured the essence of this spectacle with a quote from Hucklebury Finn: We had the sky, up there, all speckled with stars, and we used to lay on our backs and look up at them, and discuss about whether they was made, or only just happened.

Forests

The second Sources of Knowledge Forum, held in Tobermory in 2010,  explored Wildlife and Its Value to Community. One notable contribution that has relevance today was from the Nature Conservancy of Canada (NCC) who presented their Conservation Plan for the Northern (Bruce) Saugeen Peninsula.

The NCC stated that the Peninsula is “World renowned for its diversity of orchids (42 species) and ferns (20 species), this region is one of the Great Lakes’ biodiversity “hotspots” … many unique habitats occur, including alvars, sand beaches, fens and meadow marshes. Along its eastern shore, the Peninsula supports a rare example of an ancient forest, with an Eastern White Cedar that is 1,320+ years old. It is the oldest living tree in Ontario and quite possibly Canada.

Another unique feature of the Saugeen Peninsula is that it represents the largest remaining forested area in southern Ontario. According to the Southern Ontario Land Resource Information System, in 2008 the area contained 66,146.7 ha of forest cover, representing 69.15% of the total area. But today, southern Ontario has only about 25% forest cover, which is less than the minimum needed to support healthy wildlife and ecosystems. Southwestern Ontario has only 12.1% forest cover. See Environmental Commissioner’s Report 2018.

Just before the Ford government axed the position, the Environmental Commissioner of Ontario issued the 2018 Environmental Protection Report. The report stated that before European settlement, the landscape of southern Ontario was almost continuously forested.

The Report sets out the forest cover thresholds and corresponding consequences for biodiversity and aquatic systems within a watershed. These are:

  • 30% Minimum forest cover threshold is a high-risk approach that may only support less than one half of the potential species richness, and marginally healthy aquatic systems.
  • 40% Minimum-risk approach that is likely to support more than one half of the potential species richness, and moderately healthy aquatic systems.
  • 50% Low-risk approach that is likely to support most of the potential species and healthy aquatic systems

While we no longer bulldoze entire woodlands as a matter of course, the Report notes that forest loss in southern Ontario is death by a thousand cuts. We allow other land uses to fragment the forest and nibble away at the edges. Each incremental loss has big impacts on the services the forests provide to society and the wildlife they support. When a road cuts through a woodland it not only removes forest, it creates new forest edges, which can have negative impacts on interior forest-dwelling species.

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For communities with little forest cover, every small patch of forest counts as a defence against  erosion, storm water run-off, air and water pollution, greenhouse gas emissions, noise and heat. A mature, diverse forest provides functions and services (seed sources, pollen, healthy soils for regeneration, greater biodiversity) that new plantations won’t be able to provide for decades.

One of the problems is that Ontario’s land use planning rules are weak and do not prohibit clearing forests and development tends to take precedence. The key document is the Provincial Policy Statement (PPS) which sets out the general rules for land use planning in southern Ontario. Municipalities then apply these rules in their respective official plans, which must be consistent with the PPS. The PPS prohibits development or site alteration in “significant woodlands” (identified and designated by municipalities) unless it has been demonstrated that there will be no negative impacts on the natural features or their ecological functions. The PPS directs that nothing in its natural heritage policies is … intended to limit agricultural uses to continue. To protect woodland from development it must be identified and designated as significant. Small forest clearance may not be considered significant but cumulatively it probably will and in Bruce County, at least, the planners do not measure cumulative impacts.

If overall forest cover is low across the municipality, the ministry guidelines recommend that even small woodlands be considered significant, but if overall forest cover is higher, the size threshold for significance is also higher.

To increase forest cover to 40% as well as meet Canada’s carbon reduction targets,  control flooding, protect shorelines and reduce erosion, in 2008, the Ontario government created the “50 million Trees Program.” As of this year, 27 million trees have been planted across Ontario. Last month the Ford government announced that it was immediately cancelling the program to save the $4.7 million in costs. After a major nursery operation pointed out that they alone would be obliged to destroy more than three million seedlings and young trees, the Minister backtracked and postponed cancellation for a year. At the same time the government cut in half the funding for conservation authorities for flood control.

Since the start of its involvement on the Saugeen Peninsula the NCC has protected 5,865 hectares (14,490 acres). This is land permanently removed from development. Added to the National Park and other protected areas this amounts to a significant increase in protected lands in the 20 years since the NCC first bought property on the Peninsula. Nevertheless, it is worth the effort because, as the NCC pointed out at the Forum 2010, the Peninsula …represents an ecosystem of global importance for biodiversity conservation … and it provides …one of the last opportunities to protect large-scale functioning ecosystems in Southern Ontario.

In case there is any doubt about the importance to humanity’s continued existence on this planet one should read the UN Report published in May on the destruction of biodiversity and ecosystems. There is a summary here.

There is also a description of the protected areas on the Peninsula illustrated with excellent maps by the Wildlands League here.

 

Saugeen Peninsula

430 Million years of history

At the 2013 Sources of Knowledge Forum professional geologist Daryl Cowell, who lives in Tobermory, gave an excellent presentation describing the last 10,000 years of the history of the Great Lakes and the Saugeen Peninsula in particular.

Hundreds of thousands of tourists are attracted every year to the Peninsula, drawn to the stunning scenery and the possibilities of amusement on the clear water of Lake Huron and Georgian Bay. The foundation of the spectacular views, the clear water and the unique flora and fauna are the rock formations shaping the peninsula and the islands scattered throughout Fathom Five National Marine Park.

Image by Daryl Cowell. Click here for more detailed maps and information

The Saugeen Peninsula is part of the Niagara Escarpment, which reaches from Niagara Falls to Manitoulin Island and, indeed, in a great arc to Wisconsin. It began roughly 430 million years ago as a barrier chain of sponge-cored reefs that had built up on the floor of an ancient tropical sea teeming with marine life. Over millennia rivers laid down sediment and sea creatures died and were deposited on the sea floor, gradually building up layers of lime-rich sediments. Beneath these lime-rich sediments were older layers of sediments including muds, silts, sands and other lime-rich materials, deposited within a large depression on the pre-existing 2.5 billion year old bedrock. This part of the Canadian Shield forms a gigantic bowl encompassing lakes Michigan, Huron and Georgian Bay, and Erie. It is known as the Michigan Basin and it comes to the surface north of Manitoulin Island. As you drive north of Little Current you can clearly see where the sedimentary rock of the escarpment ends and the Canadian Shield comes to the surface.

In time, magnesium in the saline surface waters replaced some of the calcium in the underlying lime-rich sediments, converting them to the dolomite mineral, eventually hardening to form dolostone, which characterizes the present day Saugeen Peninsula. Dolostone is the dominant rock type on the surface of the peninsula, however shales (from mud), siltones (from silts), and other dolostones appear beneath the escarpment crest on the slopes leading to Georgian Bay. The ancient sea supported sponges, corals and a variety of shelled organisms which gradually built up an enormous reef, which, apparently, would have rivalled Australia’s Great Barrier Reef. The evidence of these ancient life forms can be found in abundant fossils in many parts of the peninsula.

In geological time, the period when the bedrock now forming the peninsula and the islands were formed is known as the Silurian. Throughout that time, climate and ecosystem changes occurred which caused the nature and frequency of the sedimentary deposits to change and these changes are visible today in the differences in the rock layers. North of Wiarton, the dolomite rock generally falls into three main “age groups” although other, older, pre-Silurian formations are visible lower down on the cliffs facing Georgian Bay. The oldest outcrops on the surface of the peninsula mostly occur at Cabot Head, Cape Croker, and Colpoys Bay. These rocks belong to the Cabot Head Formation. Lying above the Cabot Head Formation and spreading west approximately to the Bury Road and south of Cabot Head is a younger layer called the Gasport/Goat Island formations and on the west side of Bury Road to shore of Lake Huron is the youngest rock type belonging to the Guelph Formation.

The dolostone rock is pitted, often with perfectly round holes. These holes, called “pit karren”, have been formed by rainwater opening up pre-existing pores in the bedrock surface which are subsequently expanded by acids secreted from plants colonizing the rock surface. This is a type of karst landform feature which results from the solution of certain types of bedrock by weak acids in rain and from living vegetation. Karst is a suite of landforms created by solution and enhancing the subsurface movement of water  

through sinkholes, cracks and caves down to less soluble rock layers (e.g., shales). There are, for example, sinkholes and cracks which transport water accumulating in the area of Cape Hurd Road and Hwy 6 rapidly via a series of sinkholes into Georgian Bay at Dunks Bay.

Dolostone is not the only rock on the peninsula and the Islands. All over the surface of the peninsula one can find rocks which definitely do not belong. These are known as ‘erratics’ and they have been scooped up in the north and carried huge distances to the area by the glaciers during various ice ages. The glaciers also scooped out the lake basins to great depth so that all the lakes with the exception of Erie, have depths which are well below sea level and could not, therefore, have been carved out by the action of rivers.

The iconic landform in the Fathom Five Marine Park are the structures on Flowerpot Island. Wave action and falling water levels over years have eroded away weaker rock underlying thicker, stronger rock leaving behind rock pedestals which have the locally famous flowerpot shape. The large flowerpot on the island started to form roughly around 3,000 years ago.

A detailed account of the bedrock geology of the Saugeen Peninsula called Memoir 360, Paleozoic Geology of the Bruce Peninsula Area, Ontario by B.A. Liberty and T.E. Bolton

is available from the Geological Survey of Canada, at: https://geoscan.nrcan.gc.ca/starweb/geoscan/servlet.starweb?path=geoscan/downloade.web&search1=R=102382

The surface geology of the peninsula including the types of soft sediments can be found in a more recent Open File Report, Surficial Geology of the Bruce Peninsula, Southern Ontario by W.R. Cowan and D.R. Sharpe from the Ontario Geological Survey, at: https://www.google.com/search?client=firefox-b-d&q=surficial+geology+of+the+bruce+peninsula

A more readable and beautifully illustrated account to which Mr. Cowell made a major contribution is: Geology and Landforms of Grey & Bruce Counties by The Bruce-Grey Geology Committee. This can be ordered from the Ginger Press in Owen Sound.

Plastic Waste

On March 10 this year the Province of Ontario announced that it was considering a ban on plastic waste as part of a broader strategy to send less waste to landfill sites. Almost one tonne of waste per person is generated annually in Ontario and only 30 per cent is diverted from landfills by composting and recycling. According to the government this rate of diversion has not changed over the last thirty years. The Environment Minister Rod Phillips has said, “Plastics is a priority from our government’s point of view, particularly as we talk about plastics in our waterways.” The government estimates that almost 10,000 tonnes of plastic debris enter the Great Lakes each year.

In a February 2017 report by the International Joint Commission (IJC), the Canada/USA body that manages the lakes, studies have documented the occurrence of plastic debris, including plastic bags, bottles, boxes, fibres, micro-beads, and cigarette butts, in marine and fresh waters including the Great Lakes. Larger plastic debris degrades into smaller micro-plastics, and it is these smaller particles that are of particular concern. Micro-plastics generally refer to particles 5 mm or less in size and include; micro-beads from personal care products; fibres from synthetic clothing; pre-production pellets and powders; as well as degraded pieces from larger plastic products. Little is known about the fate of these smaller plastic particles and the IJC is concerned about their potential impacts on environmental and human health.

Plastic enters the Great Lakes in many ways. Most egregiously, people on the shore and on boats throw litter in the water but micro-plastic pollution also comes from wastewater treatment plants, storm water and agricultural runoff. Some plastic fibres become airborne, possibly from clothing or building materials weathering outdoors and these are probably deposited into the lakes directly from the air.

The IJC made 10 recommendations, one of which was to develop a model to determine the sources and fate of micro-plastics. In their Aug 20 2018 issue, The Conversation, an independent, not-for-profit media outlet, reported on the work of two scientists, from the Rochester Institute of Technology, Matthew J. Hoffman and Christy Tyler, who have developed a computer model to track the movement of micro-plastics in the lakes.

They found that, while plastics often accumulate in large floating garbage patches in the oceans, in the Great Lakes there may be temporary accumulation patches but they do not persist as they do in the ocean. In Lake Erie and the other Great Lakes, strong winds break up the accumulated patches and there was no evidence for a Great Lakes garbage patch. This appears to be good news except that we know that a lot of plastic is entering the lakes so if it is not accumulating in large patches, where is it?

Hoffman and Tyler’s computer model shows that most of it ends up closer to shore (see map below.) This helps to explain why so much plastic is found on Great Lakes beaches. In 2017 alone, one group of volunteers collected more than 16 tons of plastic at beach cleanups. Thus, the plastic is ending up near shore, where more wildlife is located and where we obtain our drinking water.


Average density of simulated particles in the Great Lakes from 2009-2014. Notice that there are no patches in the middle of the Lakes, but more of the particles are concentrated near the shores. Credit: Matthew HoffmanCC BY-NC-ND

The scientists estimate that over four tons of micro-plastic are floating in Lake Erie. This figure is only a small fraction of the approximately 2,500 tons of plastic that they estimate enters the Lake each year. According to their initial simulations, much of the plastic is expected to sink. This prediction is supported by sediment samples collected from the bottom of the Great Lakes, which can contain high concentrations of plastic. You can see the computer simulation of the dispersal of micro-plastics in Lake Erie here.

Another IJC recommendation was to assess the potential ecological and human health impacts of micro-plastics in the Great Lakes. One such recent study – available here.

The researchers found micro-plastic particles – fragments measuring less then five millimetres – in tap water and beer brewed with water from the Great Lakes. Since many studies indicate risks to human health when plastic particles such as synthetic polymers are ingested, clearly more needs to be known about the presence and abundance of micro-plastic particles in human foods and beverages. The PLOS study investigated the presence of micro-plastic particles in 159 samples of globally sourced tap water, 12 brands of Great Lakes beer, and 12 brands of commercial sea salt. Of the tap water samples analyzed, 81% were found to contain micro-plastic particles. The majority of these particles were fibres (98.3%) between 0.1–5 mm in length and there was an average of 5.45 particles per litre. Plastic debris was also found in each brand of beer and salt. Of the extracted particles, over 99% were fibres. The average number of particles found in beer was 4.05 particles per litre and the average number of particles found in each brand of salt was 212 particles per kg. Based on consumer guidelines, the study indicated that the average person ingests over 5,800 particles of synthetic debris from these three sources annually, with the largest contribution coming from tap water (88%).

The IJC also recognized that it is vital to change peoples’ behaviour and the only way to do that is through education. They recommended that Canada and the USA increase their funding of education programs, particularly for grades K to 12.

Tobermory Seiches

A Review of a study by John Greenhouse

A seiche (SAYSH) is a wave in an enclosed or partially enclosed body of water. Like water in a jostled tub, energy sloshes back and forth between the boundaries of the water body creating what are known as “standing waves”, not unlike those that can be seen in a skipping rope. Seiches and seiche-related phenomena can be observed on lakes, reservoirs, bays, harbours and oceans. Some can be very dramatic, but others are all but imperceptible.

On the Great Lakes a seiche derives its energy (the “jostling”) from the atmosphere. A sharp change in pressure or wind speed will produce a wave in the body of water (Figure 1). The wave is reflected repeatedly from the shores, generating standing waves with one or more peaks. The repetition time, or “period” of the oscillation is determined by the size and shape of the water body, and by its depth.  In large water bodies the period of oscillation will be several hours. As shown in Figure 1, the thermocline can also oscillate as a standing wave.

Figure 1. Wind generating standing waves on the surface and the thermocline of a lake.
Frankemann [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)%5D

In bays leading off Lake Huron the water level will rise and fall with the lake, but they also have oscillations with periods determined by the size, shape and depth of the bay itself. These harbour oscillations or seiches, have periods typically from a few minutes to an hour.

Large seiches occur every few years and, are exceptional events. They are generated by extreme weather out in the big lake and, when they arrive at a harbour, they can be hugely amplified. They are extreme events but a seiche is continual. The lake and its harbours are in almost constant but very low level oscillation because the atmosphere itself is never completely static. This continual seiche activity is most often imperceptible to observers on land or in boats due to the extremely long period and low amplitude of the wave.

John Greenhouse is fascinated by these harbour oscillations. They have already been studied quite extensively but there are nothing more than anecdotal accounts of the seiche activity in individual bays and harbours around the peninsula. Do they have characteristic and repeatable periods independent of the those in Lake Huron itself? Are these characteristics explainable in terms of the size, shape and depth of bays? Do these characteristics determine what happens when a major seiche comes from the big lake outside? Despite an extensive body of literature on the subject, there seemed to be a local knowledge gap to fill.

Figure 2. Numbered red dots indicate the location of measuring stations in this study.

Accordingly, over a four year period, John Greenhouse set up water-level monitoring stations (Figure 2) at 19 locations in Tobermory and along the western shore of the peninsula.

The frequency of a wave is the number of times per second that the wave cycles. Frequency is measured in cycles per hour (cph). The period of the wave is the time between wave crests. The period is also measured in time units. The period and frequency are inverse of each other. Frequency, the inverse of period, is measured in cycles per hour (for example, 4 cycles per hour implies a period of 15 minutes).

John has characterized each harbour in terms of the frequency of its oscillations. He found that each harbour had its own characteristic frequency that was consistent over time and it was unique to that harbour. In other words, each harbour or bay had its own “signature”. 

The dominant frequency of the harbours he studied ranged from 0.8 cph at Stokes Bay (period of 75 minutes) to 13 cph (period of 4.5 minutes) at Little Tub Harbour.  These harbour frequencies are broadly consistent with predictions based on the size, shape and depth. They are quite distinct from oscillations in the big lake, which also can be measured in the harbours but have much longer periods.

As noted above, a large seiche coming in from the lake can hugely amplify a seiche in a harbour like Little Tub with possibly damaging effects. The next step in this study may be to obtain simultaneous measurements of a large seiche on the lake before it reaches the harbour and measure the harbour’s response. From that one might be able to predict a large seiche and mitigate the effects on property.

The full paper will soon be published on the SOK website (www.sourcesof knowledge.ca). In the meantime you might enjoy reading Chapter 7 of Sherwood Fox’s book, The Bruce Beckons, who gives a wonderful description of  a very large seiche in Stokes Bay in the late 1940’s.

SOK Talks

Sources of Knowledge is not just about the annual forum. It has also been running a series of evening talks at the Park Visitor Centre auditorium. On March 13, 2019 at 7pm, Brian McHattie from Parks Canada will be giving a talk on: Iconic West Coast Orca Population in Crisis.