Contributed to Celsias.com by Jeanne Roberts
A recent report by the province of British Columbia, called Projected Sea Level Changes for British Columbia in the 21st Century and compiled from B.C. fisheries and natural resources departments, is targeted at helping B.C.'s coastal communities prepare for, and protect against, climate change.
According to B.C.'s Environment Minister, Barry Penner, the report represents the first comprehensive analysis of sea level change for the province's coastline since 1997, and should help individuals and towns to prepare for what most believe will be inevitable sea level rise. The problem is, the rise will be highly variable, and the largest variations will likely be along the coast.
The cause is melting continental glaciers and ice caps, and warming of the upper ocean, and will affect coastal communities worldwide. In British Columbia, unique factors like climate, subsidence and vertical land movements may have additional, regional effects.
According to the study, released last year, the Fraser River delta and Haida Gwaii are among the most vulnerable areas, and sea level rise by 2100 will range from 11 centimeters (4.33 inches) at Nanaimo to more than 50 centimeters (19.68 inches) for the mouth of the Fraser River, which empties into the bay west of Vancouver and from there into the North Pacific.
The continental glaciers in question are the Arctic and Antartica. In the latter, the Wilkins Ice Shelf, connected to the continent by a mere 500-meter (1,640-foot) wide tongue of ice, hangs precariously out into the ocean. Once covering 16,000 square kilometers, the ice shelf is still the size of Connecticut, on the U.S. Eastern Seaboard, and is currently bound to the continent by a tongue of ice which was, as recently as 1950, 100 kilometers (62 miles) wide.
In the Arctic, ice melt reached a record in 2007. In 2008, this record melting swamped an Arctic park in the northeastern part of Canada, doing so much damage hikers and outdoor enthusiasts had to be airlifted to safety.
Melting glaciers are also contributing to sea level rise, and the ultimate effect of all this fresh water - which occupies more space than saline ocean water - is an additional rise in sea levels via displacement.
Add to these local changes - like the subsidence of river deltas like the Fraser; the rebounding of land that is still taking place 10,000 years after the last ice age; and the tectonic plate movements along the B.C. coast, as the Juan de Fuca plate pushes underneath the North American plate, raising Vancouver Island two to three millimeters a year - and the potential for serious coastal inundation becomes not a fictional scenario but a frightening possibility. A possibility made even more alarming by the 500 to 600-year frequency of major earthquakes, which cause land to drop as much as to two meters.
"The anticipated changes in sea level could have significant consequences for areas currently protected by dikes (such as the Fraser and Squamish deltas), where coastal erosion is already an issue (east Graham Island, Haida Gwaii), or where development and harbor infrastructure is close to present high tide limits," the report notes. "Of particular concern will be extreme weather events, such as storm surges, occurring at the same time as these high sea levels."
Even though the B.C. government is into the third year of 10-year, $100 million flood protection program, Penner insists the study's finding show a definitive need to continue reducing greenhouse gas emissions to save locales like the Fraser River delta, where sedimentation is actually pushing the land downward.
As Stephen Rees points out, the lack of dredging in secondary channels of the Fraser River creates a situation where a seismically unstable region is sinking even as ocean levels rise.
"Once the big earthquake hits, within minutes the land all falls back down a meter or so and then the big tsunami hits, and it's not going to be fun."
University of British Columbia (UBC) scientists concur. In a study published in the December 31, 2008 edition of the journal Nature, UBC researchers Pascal Audet, Michael Bostock, Nicolas Christensen, and Simon Peacock examined how water trapped in a portion of the Cascadia megathrust fault under the Vancouver Island area escapes at intervals after sufficient pressure has built up. This escape, for its part, helps "lubricate" the area's opposing tectonic plates, causing them to slip and explaining the regular tremors under Vancouver Island.
Celsias.com is a Premier Content Partner of SustainLane. Be Informed, Take Action on Climate Change - www.Celsias.com.
