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Atlantic Canada on path to sea level rise

An illustration included in Canada’s Changing Climate Report, released Tuesday, which shows projected relative sea level changes in the year 2100 for a high emission scenario at 69 coastal locations in Canada and the northern United States.
An illustration included in Canada’s Changing Climate Report, released Tuesday, which shows projected relative sea level changes in the year 2100 for a high emission scenario at 69 coastal locations in Canada and the northern United States. - Contributed

Report outlines risk of storm surges, flooding, coastline erosion

OTTAWA, Ont. —

A new report on climate change has found that parts of Atlantic Canada will experience higher-than-average sea level rise in the coming decades, leading to more storm surges and flooding, ecosystem and infrastructure damage and coastline erosion.

And while lowering global emissions can mitigate some of the worst-case outcomes, experts say this trajectory cannot be reversed and governments need to also focus on protecting infrastructure and planning for the impact of these projected rises in at-risk communities.

Tabled on Tuesday, the sweeping report called Canada's Changing Climate was led by Environment and Climate Change Canada and authored by government scientists across a number of departments.

One of the main findings of the report is that scientists have high confidence that Nova Scotia and P.E.I., and parts of New Brunswick and the island of Newfoundland, will experience sea level rise higher than the global average during the coming century.

Thomas James, a research scientist with the Geological Survey of Canada who authored the section of the report that looks at sea level change, said for all possible emission scenarios, global sea levels are expected to rise, and that rise will be more pronounced with higher global carbon emission scenarios.

According to the report, global mean sea level is projected to rise by 28–98 cm by the end of the century, but, under a high-emissions scenario, the only area of Canada expected to see between 75 and 100 cm is Atlantic Canada.

James said that’s because sea level rise is compounded in the region by something called postglacial rebound.

“In the last ice age, the centre of Canada was loaded with thick ice sheets that were three to four kilometres thick. They pushed down the surface of the Earth, and deep in the Earth the mantle material actually … behaved like very thick molasses, and on the edge of the former ice sheet the land actually rose a bit,” he explained.

“Now that the ice is gone, the centre area that was depressed is now rising and peripheral areas, which includes parts of the Maritimes, that were elevated are now slowly sinking. Where the land is sinking slowly, it adds to the global sea level rise, so projected relative sea level rise is bigger than the global value.”

In places like Halifax, James said, this could mean a 20-cm increase in mean sea level and a four times increase in flooding by mid-century — the next two or three decades — even in a low-emissions scenario. In a high-emissions scenario, the impact could double.

The report says large-impact events, such as high water levels reached once every 50 years at Halifax in the past, might occur as frequently as every two years by mid-century under the relative sea level rise caused by a high-emissions scenario.

To make matters worse, James said in some more northern areas, like in the Gulf of St. Lawrence and along the Labrador coast, sea ice duration is expected to decrease, causing less shoreline protection from storm surges.

According to data available via sealevelrise.com, a joint initiative of conservation groups like the Halifax-based Ecology Action Centre and Newfoundland and Labrador Conservation Corps as well as federal and provincial governments and universities, 60 per cent of the population of New Brunswick, 70 per cent of the population of Nova Scotia and 90 per cent of the population of Newfoundland and Labrador live in coastal communities, and no place in P.E.I. is further than 16 kilometres from the coast.

With this in mind, coupled with the fact that scientists say the Earth is on an irreversible path to sea level rise, it’s little wonder why people like Nancy Anningson, the Ecology Action Centre’s senior co-ordinator of coastal adaptation, are pushing governments to start preparing for the inevitable.

“What we need to do is adapt, and that's for the (infrastructure) that already exists, and protect, which is for the future — like protecting ecosystems, protecting us from putting ourselves where we shouldn’t be.”

In Nova Scotia, where sea level rise is projected to be the highest, a bill called the Coastal Protection Act was tabled in March and aims to legislate some of the items on the protection side such as limiting coastal developments and protecting coastal ecosystems like wetlands and dunes and marshes that buffer storms and protect the coastline.

Anningson said while governments are catching on to the idea of protection, there is little being done to adapt homes and infrastructure that are currently in danger.

“The next step is to start to figure that out … and there are options for how to adapt as long as we acknowledge this is happening and prepare,” she said.

Some of those options include things like moving or raising structures, or waterproofing basements.

“We need to get information out to people and make them more aware of how this is impacting them and where the biggest risks are,” Anningson said. “We need to start working on that stuff, because this is happening.”

As for reducing the worst-case scenarios presented by sea level rise, James said the only way is to put the entire globe, not just Canada, on a pathway of low carbon emissions.

“That's what will reduce climate change and reduce the impacts of climate change,” he said.


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