Last year was the hottest on record for the ocean, an upward trend only expected to continue as it wreaks havoc on coastal communities and spurs irreversible losses to marine ecosystems.
Ocean warming has cascading effects, melting polar ice and causing sea-level rise, marine heat waves and ocean acidification, the United Nations’ panel of climate experts made clear on Monday.
Sea-level rise has doubled in the last three decades, reaching a record high in 2021, the Intergovernmental Panel on Climate Change reported. Rising seas, coupled with more extreme weather, are setting the stage for a perfect storm of flooding for coastal communities.
Ocean surges during storms will tear apart coastal infrastructure — as it did during hurricane Fiona last year on Canada’s East Coast — increasing annual flood damage by up to three orders of magnitude across the globe by the end of the century, IPCC said.
But climate impacts on the ocean have localized and serious ripple effects along the B.C. coast, particularly in the Salish Sea, oceanographer Jennifer Jackson said.
Oceans play a central role in any adaptation strategies given they are the globe’s biggest ally in the fight against climate change — sinking massive amounts of C02 and absorbing more than 90 per cent of the excess heat those emissions create, according to Canadian scientists and conservationists.
Increasing water temperatures, lower levels of oxygen and increasingly acidic oceans impact the survival of important marine species; Pacific salmon are a prime example, said Jackson, section head of ocean modelling for Fisheries and Oceans Canada’s (DFO) Pacific branch.
Once abundant in B.C. — and foundational to the food security and culture of First Nations — most salmon stocks are on the brink of collapse due to the cumulative effects of warming waters, changing food webs, habitat destruction, overfishing and the increased risk of disease or parasites from fish farms.
“Salmon have a very specific temperature range, and when you go above that, it impacts things like their growth or reproductive rates,” she said. “Eventually, if combined with other stressors, it can lead to mortality.”
Commercially important species like salmon may flee traditional habitat ranges in search of cooler water nearer the North or South poles and across international boundaries, impacting fisheries already in decline and possibly heightening international tensions.
Shellfish, another food source and economic driver for coastal communities, are increasingly vulnerable to die-off in warm water temperatures that can trigger the growth of toxic algae or harmful bacteria, Jackson said.
That’s if they don’t boil in their shells on shore along with up to a billion other creatures in the intertidal zone during atmospheric heat waves (also predicted to become more frequent), like the B.C. heat dome in July 2021, which killed 619 people.
Ocean warming means no sea stars on the seashore
The devastation of sea stars on the B.C. coast, particularly the massive, many-armed sunflower sea star, is another example of the deadly combination of warmer waters and disease, Jackson said.
Sea star wasting disease (SSWS) — caused by a virus that surged in 2013 in tandem with a massive marine heat wave on the West Coast dubbed “the Blob” — caused white lesions on up to 20 different species in waters from Mexico to Alaska, which ultimately reduced the once ubiquitous sea creatures to mush.
The collapse of sunflower star populations, in particular, had a nasty ripple effect on marine ecosystems. A primary predator of sea urchins, the sunflower stars’ disappearance left the spiny sea creature unchecked to devour kelp forests in B.C waters, resulting in a 30 per cent decline of habitat vital to a host of marine animals, including otters, seals and fish.
Marine heat waves like the Blob — which boosted B.C.’s ocean water temperatures by as much as 3 C — will increase in frequency if emissions from burning fossil fuels aren’t radically reduced, the IPCC said.
After the Blob ebbed in 2016, warm water lingered for at least two more years in the deep fjords along B.C.’s central coast, which typically maintain cooler temperatures than water at the ocean’s surface, Jackson’s research showed.
A comparative study of four coastal inlets (the Douglas Channel along with the Rivers, Knight and Bute inlets) showed deep-water temperatures in the fjords had increased significantly over 70 years while oxygen levels have dropped.
The deep-water temperatures in the fjords — fairly representative of the inlets along the B.C. coast — increased as much as 1.3 C over that time span, twice the global average for open ocean waters at the same depths, Jackson’s study found.
A single degree of warming may not seem like much, but deep water below 200 metres generally fluctuates by fractions of a degree, so a dramatic increase over a relatively short period is noteworthy and concerning, Jackson said. Oxygen levels in the inlets’ waters have also dropped by up to 20 per cent, she said, noting that increasing hypoxia, or dead zones, means marine animals must move or perish.
Hypoxic zones in the ocean occur naturally, but dropping ocean oxygen levels are accelerated by global warming worldwide. Warmer waters hold less oxygen. And warmer water in combination with pollution draining into the ocean coastal areas — like fertilizer, sewage and animal waste — provide the “nutrients” and conditions for excessive algae growth, which also rapidly depletes oxygen.
Warmer, less-oxygenated water on the ocean’s surface is also more buoyant than deeper, cooler water and hinders the natural “mixing” of water by waves and wind that can circulate more oxygen upwards, Jackson said.
A third climate impact causing big changes in the Salish Sea is ocean acidification, Jackson said, particularly in the Discovery Islands region off the east coast of Vancouver Island near Campbell River.
“It’s not directly linked to temperature but is dependent on how many greenhouse gases we put into our atmosphere,” she said.
The absorption of the increasing CO2 in the atmosphere into the ocean drops the level of calcium carbonate in the water — a building block for many creatures’ shells or skeletons, including crabs, shellfish, prawns, corals, sea urchins and tiny marine snails that fish like salmon depend on for food.
IPPC report is ‘bleak’ reading
The IPCC report and climate effects on the ocean make for “bleak” reading, said Alexandra Barron, national ocean director for the Canadian Parks and Wilderness Society.
Restoring and protecting marine ecosystems that sequester carbon and bolster biodiversity in “blue carbon” ecosystems, like saltwater marshes, kelp forests or eelgrass meadows, is one recommendation of the IPCC report. As is shifting to sustainable, small-scale fisheries and the conservation of up to 50 per cent of lands, oceans and freshwater systems will also help stem climate change impacts.
Barron applauded a historic pledge Canada and more than 190 other nations signed in December to protect 30 per cent of the planet’s lands and waters. But the bar is already shifting, Barron said.
“IPCC is confirming that 30 per cent is a stepping stone,” she said.
Establishing marine protected areas (MPAs) in partnership with Indigenous Peoples in Canada’s oceans will be important to ensure climate adaptation and food security for coastal communities, she added.
The proposal for a massive network of MPAs spanning two-thirds of the B.C. coast stewarded by First Nations, the province and the federal government can act as biodiversity banks and fish nurseries to help rebuild fisheries, Barron said.
The IPCC report clarifies that the need for strongly protected ocean conservation areas on the West Coast and the ocean at a global level is urgent, she said.
“The longer we wait to act — whether it’s establishing climate-smart MPAs, restoring carbon sinks, or reducing land conversion — the less of an impact these strategies will have,” she said.
“Time is of the essence if we want to even dream of staying within 1.5 degrees.”
By Rochelle Baker, Local Journalism Initiative Reporter
Original Published on Mar 24, 2023