‘Double whammy’ in Atlantic Canada
Sinking land mass, increasing water levels threaten coastline
Editor’s Note: This story is part of a SaltWire Special Report examining the rising seas around Nova Scotia.
The secluded West Hants cemetery whispers peace and tranquility.
But the calm that has washed over Riverview Cemetery in Upper Burlington for the past 185 years is being usurped by ever-encroaching sea water overflowing the Kennetcook River.
“About 30 years ago, this started flooding pretty regularly with the tide,” Randy Barkhouse said of the rural cemetery where his parents and many of his relatives have been laid to rest.
“You can see the high-water mark on some of these stones.”
That the high-water mark is steadily getting higher is no surprise to the scientific community.
“In Atlantic Canada, the sea level is rising,” said Gavin Manson, a coastal geoscientist with the Geological Survey of Canada.
The sea that consistently buffets and pounds more than 8,000 kilometres of Nova Scotia coastline is expected to rise in the range of a metre by 2100.
Manson said there are two components to global sea level rise; the typical climate change story of melting glaciers and ice caps and the fact that as water warms, it expands.
A third factor that affects Atlantic Canada is that the land beneath us is sinking even as the sea level rises. Manson said at the peak of the last glaciation, about 21,000 years ago, there was a very thick ice centre over the Hudson Bay region. The depressed crust underneath that ice sank as the ice grew. In Atlantic Canada, the ice cover was thinner.
“Because of the difference in ice thickness between the two areas, we were actually elevated more than normal,” said Manson, who works out of the Bedford Institute of Technology.
“The material underneath the earth’s crust is quite fluid. It’s kind of like sitting on a waterbed. When you sit down, when you put your bum down, it sinks underneath you but it rises up around the edges. We were on the edge and we were actually a high ground surface compared to where we were prior to glaciation.”
But with deglaciation, Manson said the material underneath the earth’s crust that shifted toward the Atlantic coast is now gradually moving back toward Hudson Bay.
“That area (Hudson Bay ) is actually rising and our land here is actually sinking, trying to go back to where it was prior to the glaciation,” Manson said.
“Here in Atlantic Canada, we have sort of a double whammy.”
The double whammy of rising water and sinking ground plays out in consistent erosion of coastal land and more devastating storm surges that take a significant toll on coastal infrastructure, particularly buildings and roads.
The relative sea level rise in the Halifax area and most of the province totals 3.2 millimetres per year, arrived at by the coincidence of the land sinking by 1.6 millimetres per year and the sea rising by 1.6 millimetres, Manson said.
“It doesn’t sound like a lot but that’s 32 centimetres per century, which starts to add up,” he said.
Manson adds it up to sea levels for Halifax and most of Nova Scotia being three-quarters of a metre higher by century’s end than in the year 2000. Manson’s projections — based on Intergovernmental Panel on Climate Change reports that are a collaborative effort of 830 scientists from 80 countries — combines the land-sinking rate with the projected global mean sea level change.
The provincial government’s action plan for climate change predicts that sea level will rise by a projected average of 1.05 or 1.06 metres in much of Nova Scotia by 2100, with an estimate of 1.10 metres for the areas of western Cape Breton, Sydney, Guysborough and Kentville.
Tim Webster, a research scientist with the Applied Geomatics Research Group at the community college in Middleton, has been producing highresolution flood risk maps for coastal communities and municipalities around the province for more than 15 years. He said sea level rise will accelerate the frequency of storms that had been considered a once-in-50years or a once-in-a-century event. The storm surges of yesteryear, riding higher sea levels, can be expected to produce more flooding and more damage to infrastructure.
“That (once-in-20-years storm surge) will get to that same elevation a lot more frequently,” Webster said.
He said more than coastal communities are at risk.
“Many of our communities are built along estuaries, given our historic link to the sea. If we’re not right on the coast, then we’re up a river not very far from the coast, where the interaction of the sea still plays a role.”
So, are we up that murky creek without a paddle?
Jason Hollett, executive director of the climate change team with the province’s Environment Department, said no one is waving a white flag.
“Nowhere in Nova Scotia is more than 90 kilometres away from the ocean and a lot of our critical infrastructure is built really close to the water, whether it’s lakes or the ocean,” Hollett said.
“But there are two sides to the climate change coin. There’s reducing greenhouse gas emissions on the one side and there is preparing for the impacts that are going to happen.”
The provincial government says it has reduced greenhouse gas emissions, a significant driver of climate change, by 17 per cent from 1990 levels and is on track to reach a 24 per cent reduction by 2020.
The reduction of greenhouse gas emissions fall into the category of trying to reduce the rate at which our climate is changing rather than trying to reverse what is already happening. To combat the impacts of climate change and sea level rise requires political decisions, weighing the risks against the cost to mitigate them.
The most common strategy in Canada is to protect infrastructure with abutments and breakwaters in front of the shore, Manson said.
“The issue with protection is that once it is in place it requires maintenance,” he said. “It’s a long-term commitment.”
Another approach is to retreat, moving infrastructure further back from the coast or prohibiting future development in certain areas.
“What we need to do is get a good understanding of the impacts and then have good conversations with our communities ... to say what is the most appropriate ways to deal with the impacts,” Hollett said.
Any plan will require government leadership. Ottawa, the province and its municipalities share jurisdiction and authority over coastal matters and cracking the code of who is responsible for what is often complicated.
The province is in the process of consulting with the public on coastal protection legislation that could be introduced later this year.
On a recent funding announcement stop in Dartmouth, Catherine McKenna, the federal minister of environment and climate change, said her department is a strong partner “but we need to be working with local officials, and, of course, we need to be tackling climate change.”
“We know in the long term if we don’t do anything, we are going to have absolutely huge challenges.”
In Upper Burlington, Barkhouse is well aware of the challenges posed by rising waters.
A half century ago, a rebuilt Acadian dike shielded the cemetery and the surrounding marsh from floodwaters. Two years ago, Barkhouse built a barrier facing the river to protect the 130 graves against flooding. Now, he has resigned himself to do the same on the other three sides of the cemetery.
“This marsh here, it only flooded a few times a year on the high tides, now it floods practically every time the tide comes in,” said Barkhouse, the retired director of academic computing services at Dalhousie University,
“Even if you built this dike another two feet higher ... maybe it would hold things off for another 30 years. But at some point, unless somebody or some entity keeps raising the dike here, you are going to have a cemetery like this flooded. It will just flood regularly. These tombstones will regularly be under water.”