Building on the research summarized in the Canada Country Study, much of the recent climate change research in the coastal zone has involved more detailed assessment of vulnerabilities related to specific locations, often through the use of case studies.

Impacts on the Marine Coasts

"Many coastal areas will experience increased levels of flooding, accelerated erosion, loss of wetlands..., and seawater intrusion into freshwater sources as a result of climate change."⁽¹⁵⁾

The impacts of climate change on Canada's three marine coasts will result primarily from changes in sea level and the extent and severity of storms.⁽³⁾ Increased wave energy, reduced sea-ice cover, increased ground temperatures and enhanced storm-surge activity would also contribute to the net impacts, with significant implications for coastal settlements and infrastructure.⁽³⁾ In general, climate change is expected to exacerbate existing hazards throughout the coastal zone.⁽¹⁶⁾

Atlantic Coast

"In the Maritimes, rising water levels could impact a wide range of human structures and activities... flooding and dyke breaching in the Bay of Fundy is of particular concern."⁽¹⁷⁾

The analysis of Shaw et al.⁽⁹⁾ identified more than 80% of the coastlines of Nova Scotia, New Brunswick and Prince Edward Island as being moderately to highly sensitive to sea level rise (Figure 1). Highly sensitive areas include the entire North Shore of Prince Edward Island, the Gulf Coast of New Brunswick, much of the Atlantic coast of Nova Scotia and parts of the urban centres of Charlottetown and Saint John. The rugged, rocky coast that characterizes much of Newfoundland and Labrador is generally considered to have low sensitivity to sea level rise, but there are areas of lower lying, moderately and highly sensitive coastline in that province where several communities are located.

Accelerated sea level rise would inundate coastal lowlands and erode susceptible shorelines. Parts of the coast are expected to be permanently submerged,⁽¹⁰⁾ while freshwater coastal marshes could become salt marshes and dykes enclosing areas lying below current high tide would have to be raised to avoid inundation by storm surges. Rapid sea level rise could also submerge existing salt marshes. This will place at risk regions where marshes are unable to migrate inland, due, for example, to existing infrastructure. Sea level rise and storm impacts have also been related to forest decline at sites lying close to sea level, as a result of increasing water table height and saltwater intrusion.⁽¹⁸⁾ Saltwater intrusion into coastal aquifers is also a concern for coastal communities and activities dependent of these aquifers for freshwater.

In addition to sea level rise, changes in storm frequency and intensity, as well as changes in sea-ice cover due to climate change, could potentially affect the Atlantic region.⁽¹²⁾ More frequent storms would not only be a concern in themselves, but would also increase the probability of intense storms occurring in conjunction with a high tide, thus increasing the risk of extreme water levels and coastal flooding. A decrease in seasonal sea-ice extent would result in increased wave development and wave energy, and cause increased coastal erosion during winter.

Recent case studies allow a preliminary assessment of the potential impacts of climate change at the local and regional scale. For example, in Charlottetown, where relative sea level has risen about 32 centimetres since 1911, accelerated sea level rise induced by climate change could create significant problems for urban infrastructure.⁽¹⁹⁾ When high sea level is considered in combination with the impacts of more intense storm surges, significant economic impacts could result (see Box 1). Along the north shore of Prince Edward Island, the combined effects of rising sea level, decreased sea ice and increased wave energy would result in greatly enhanced coastal erosion. A doubling of present coastal erosion rates would lead to a loss of 10% of current assessed value in the detailed study area in 20 years, and almost 50% in 100 years.⁽¹⁹⁾ Such erosion would also affect saltwater marshes and coastal dunes, both of which are significant for the tourism industry.⁽¹⁹⁾

BOX 1: What are the costs of sea level rise in Charlottetown, Prince Edward Island?⁽¹⁹⁾

Another sensitive region is the head of the Bay of Fundy, where increased flooding and dyke breaching is a potential consequence of future climate change. Figure 3 depicts the extent of potential flooding of present-day Truro, Nova Scotia, if it were subjected to a storm surge similar to that of the 1869 Saxby Gale (the highest historic water level event in the upper Bay of Fundy⁽²⁰⁾. The extent of potential present flooding reflects the 44-centimetre rise in sea level that has occurred since that time. The extent of flooding would be even higher in the future as a result of accelerated sea level rise. Degradation of coastal salt marshes due to climate change is also an important concern in this region (see Box 2).

BOX 2: Fate of salt marshes in Atlantic Canada⁽²¹⁾

Tidal salt marshes in Atlantic Canada are diverse and highly productive ecosystems. They exist within a small elevation range and are assumed to maintain elevation in equilibrium with changes in sea level. However, accelerated sea level rise resulting from climate change could mean that salt marshes are unable to maintain this equilibrium, and that increased tidal flooding could result in loss of the marshes or conversion to other types of vegetation. As part of a research project examining the vulnerability of Atlantic salt marshes, researchers found that salt marshes are generally resilient to present rates of sea level rise. However, they also concluded that some marshes may become submerged in the future as a result of accelerated sea level rise induced by climate change. The marshes studied were also found to be sensitive to sediment supply, and human-induced hydrological and management changes. Coring for Spartina patens in a salt marsh. Photo courtesy of Gail Chmura.

Figure 3: Projected flooding of present-day Truro, Nova Scotia, based on a storm surge sea level similar to that of the 1869 Saxby Gale(62). Simulation courtesy of Natural Resources Canada and Fisheries and Oceans Canada.

Climate change and sea level rise may also exacerbate other coastal zone hazards. For example, many communities in Newfoundland and Labrador have developed at the base of steep slopes, where there is risk of damage from landslides and avalanches.⁽²²⁾ As these are often triggered by extreme climatic events, there is potential for increased frequency of such hazards as a result of climate change.

Arctic Coast

"Portions of the Beaufort Sea coastline are now undergoing rapid coastal retreat, accentuated by permafrost melting."⁽¹⁷⁾

The coastline of the Canadian Arctic is characterized by biophysical processes and socio-economic activities that are greatly influenced by sea ice, which at present covers most of the coastal, inter-island channel, and ocean regions for 8 to 12 months of the year. The past 3 to 4 decades have seen a significant decrease in the extent of seasonal sea-ice cover, as documented by satellite imagery (e.g., reference 23; see Fisheries chapter). This trend is projected to continue under scenarios of future climate change, such that some studies project only very limited summer sea-ice cover by the end of this century.⁽²⁴⁾

Changes in sea-ice cover will likely be the most significant direct impact of climate change on the northern coastal region, with potential consequences for the breadth of the Arctic coastline. Reduction in sea-ice cover, and corresponding increase in the extent and duration of open water conditions, would impact northerners by affecting travel, personal safety, accessibility to communities and hunting grounds, and other traditional activities. A reduction in seasonal sea-ice coverage could also open large areas of the Arctic Archipelago, including the Northwest Passage, to increased marine shipping (see Transportation chapter). While this could present significant new opportunities for economic development, concerns have also been expressed regarding negative impacts on Arctic marine ecosystems⁽²⁵⁾ and traditional ways of life, as well as potential sovereignty and security issues.^{(26, 27)}

Rates of shoreline change in the Arctic would be altered both by changes in sea ice and by changes in relative sea level resulting from global warming. Areas now protected from wave action by persistent sea ice would be more severely impacted than areas that are seasonally reworked by waves at present. The impacts of increased wave activity would be amplified in areas such as the Beaufort Sea coast, including the outer Mackenzie Delta and Tuktoyaktuk Peninsula, which consist of poorly consolidated sediments, often with significant volumes of massive ground ice, and are undergoing submergence at present (see Box 3). Along terrestrial slopes in the coastal zone, increased ground temperatures and permafrost degradation could reduce slope stability and increase the frequency of landslides⁽²⁸⁾ thereby presenting risks for community and industrial infrastructure.

BOX 3: Sea level hazards on the Canadian Beaufort Sea coast⁽²⁹⁾

This study undertook a regional analysis of the sensitivity of the Canadian Beaufort Sea coast to sea level rise and climate warming, using historic data to examine the influence of weather conditions, ice cover and water levels on erosion. Results indicate high variability across the region, especially with respect to storms and water levels. For highly sensitive areas, characterized by high past and present rates of erosion, a GIS (geographic information system) database was used to create an index of erosion hazard. A storm-surge model was also developed to help evaluate potential flood risk under future conditions. Beaufort Sea coast. Photo courtesy of Natural Resources Canada.

Case studies in the communities of Tuktoyaktuk^{(30, 31, 32)} and Sachs Harbour,⁽³³⁾ both located along highly sensitive coasts, document ongoing impacts that would be amplified by future climate changes. Parts of Tuktoyaktuk experienced more than 100 metres of coastal retreat between 1935 and 1971. This erosion was responsible for the destruction or relocation of several community buildings. Introduction of protection measures in 1971 has resulted in stabilization at about the 1986 shoreline position, but has required considerable maintenance. Researchers noted that, even if erosion in the community is halted, the peninsula on which it is located is likely to be breached at its southern end in 50 to 100 years,⁽³⁰⁾ and that the island that protects the harbour mouth at present is also likely to be eroded away over the same timeframe.⁽³²⁾ Based on local observations, coastal erosion and permafrost degradation are also issues in Sachs Harbour on Banks Island. Recent changes in the extent and predictability of sea-ice cover have been identified by community residents as new challenges to maintaining traditional ways of life.⁽³³⁾

Pacific Coast

With the exception of the outer coast of Vancouver Island, relative sea level has risen along most of the British Columbia coast over the past 95 years.⁽³⁴⁾ However, the rate of relative sea level rise has generally been low, due to the fact that geological uplift (tectonics) has largely offset the increase in most areas.⁽³⁵⁾ This fact, combined with the steep and rocky character of the Pacific coast, results in this region having an overall low sensitivity to sea level rise. Nevertheless, there are small but important areas of the Pacific coast that are considered highly sensitive,⁽¹⁰⁾ including parts of the Queen Charlotte Islands,⁽¹⁰⁾ the Fraser Delta and unlithified sand cliffs at Vancouver,⁽¹⁰⁾ and portions of Victoria.⁽³⁶⁾ The main issues of concern include breaching of dykes, flooding, erosion, and the resultant risks to coastal ecosystems, infrastructure^{(34, 36, 37)} and archaeological sites.⁽¹⁷⁾

The Fraser Delta, which supports a large and rapidly expanding population, is one of the most highly sensitive areas on the Pacific coast. Parts of the delta are already below sea level, with extensive dyke systems in place to protect these lowlands from flooding.⁽³⁷⁾ Relative sea level is rising in this region, continually increasing the risk of erosion and shoreline instability, flooding and wetland inundation. Accelerated sea level rise resulting from climate change would further increase these risks.⁽⁹⁾ Box 4 describes some potential impacts in the delta region, assessed as part of a broader study of the Georgia Basin. In addition, the Fraser Delta is an area of relatively high seismic risk, and the potential impacts of an earthquake on the stability of the delta could be worsened by higher sea levels.⁽³⁸⁾

BOX 4: Impacts of sea level rise in the Fraser Delta⁽³⁷⁾

Climate change and sea level rise would exacerbate other coastal hazards. Higher mean sea levels could increase the potential damage associated with tsunamis (ocean waves generated by submarine earthquakes). Vancouver Island's outer coasts and inlets are most vulnerable to this hazard.⁽³⁹⁾ Another concern is a scenario in which high tides, El Niño influences and storm events coincide to produce short-lived, extreme high sea levels.⁽³⁶⁾ For example, during the most recent El Niño Southern Oscillation event, a sea level increase of 40 centimetres resulted in as much as 12 metres of coastal retreat in some areas.⁽⁴⁰⁾

Impacts on the Great Lakes-St. Lawrence Coast

Over 40 million people live within the Great Lakes Basin, and the lakes have greatly influenced the settlement, economic prosperity, and culture of the region.⁽⁴¹⁾

Precipitation, temperature and evaporation are the predominant climate variables controlling water levels in the Great Lakes.⁽⁴²⁾ Fluctuating water levels are a natural characteristic of these lakes. For example, during the period of record (from 1918 to 1998), lake levels have fluctuated within ranges of 1.19 metres for Lake Superior and 2.02 metres for Lake Ontario.⁽¹¹⁾ Future climate changes, such as those projected by the IPCC, are anticipated to result in an overall reduction in net water supplies and long-term lake level decline, such that average water levels could decline to record low levels during the latter part of this century (references 14, 43, 44; see Water Resources chapter). Climate warming would also reduce the duration of lake ice cover, which presently offers seasonal protection for much of the shoreline from severe winter storms.

Water level changes of the magnitude projected by recent studies (30-100 centimetres by 2050; reference 8) could affect the Great Lakes coastal region by restricting access of boating and shipping at docks, marinas and in connecting channels (see Figure 4). Port infrastructure used by the Great Lakes shipping industry would be similarly affected, and lower lake levels could force vessels to decrease their cargo capacity in order to continue using existing harbours and shipping lanes (see Transportation chapter).

Figure 4: Impacts of recent low Great Lakes water levels on the Lake Huron shoreline at Oliphant, Ontario. Photo courtesy of Ryan Schwartz.

Lower lake levels would also impact beaches, with the amount of new exposure a function of water depth, lakebed composition and slope, and water level decline,⁽⁴⁵⁾ such that larger beach surfaces could increase recreation space. However, researchers have found that water levels projected to occur under a range of climate change scenarios are generally well below those desired by recreational users.⁽⁴⁶⁾ Furthermore, exposed mud flats could reduce shoreline aesthetics, and there is the potential that exposed lakebeds could include toxic sediments.⁽⁴³⁾

High water levels and storm-induced flooding are ongoing problems for commercial, residential, agricultural and industrial activities in the Great Lakes coastal region.⁽⁴⁷⁾ While lower lake levels could reduce the frequency and severity of flood risk, this could be counterbalanced by pressure for development closer to new shorelines.⁽¹¹⁾

Other coastal infrastructure could also be affected by lower water levels resulting from future climate change. For example, municipal and industrial water intakes have been designed to function within the historical range of lake level fluctuations.⁽⁴⁸⁾ Water intakes located in relatively shallow water, such as those in Lake St. Clair, may experience increased episodes of supply, odour and taste problems due to insufficient water depth, and increased weed growth and algae concentrations.⁽¹¹⁾