With a ‘super’ El Niño on the way, B.C. is likely to have a much warmer-than-usual winter this year.
The warm weather will have a number of impacts on the province, from a low snowpack to southern marine animals swimming up the coastline.
An El Niño is a naturally occurring climate pattern, starting when Pacific Ocean waters begin to warm up along the equator, changing the hemispheric circulation patterns across much of the world.
By definition, an El Niño occurs when those water temperatures increase by 0.5°C. It is considered weak when the warming is between 0.5°C and 1°C, and it is considered very strong when the warming is over 2°C.
“And that’s what we’re expecting this year,” said Bill Merryfield, a research scientist with Environment and Climate Change Canada (ECCC).
In fact, most forecast models predict that this El Niño will warm those waters by over 3°C — something that hasn’t happened for at least 100 years.
“Now, some portion of this ocean temperature increase is due to the overall warming of the planet, but even when that’s factored in, this is shaping up as a historic event that will likely have major impacts across the globe,” Merryfield said.
What are the impacts of an El Niño?
During normal ocean conditions, winds (called trade winds) blow west across the Pacific Ocean, bringing warm water to Asia and Australia and letting cooler water rise along the west coast of the Americas.
However, when there is an El Niño, the trade winds will weaken or reverse, allowing warm water to move to the Americas, in turn heating the air and changing how clouds and storms form.
In a normal El Niño, the western half of Canada sees normal or above-normal temperatures in the winter, said Merryfield.
“Particularly on the west coast, where a couple of degrees one way or the other might put us on either side of the freezing mark, we might expect to have more winter precipitation falling as rain versus snow, which would have a significant effect on the snowpack,” he said.
Merryfield shared data from previous very strong El Niños (when the warming of that Pacific Ocean water at the equator is over 2°C) that occured in 1982-1983, 1997-1998, and 2015-2016.
At the ECCC’s weather station at Vancouver International Airport, the historical (from 199 t0 2020) temperature norm in the winter is 4.2°C. In 1982-1983, the average temperature rose to 5.6°C. In 1997-1998, it rose to 5.5°C. And in 2015-2016, it was at 5.7°C.
How will this year’s super El Niño affect B.C.?
Merryfield said that B.C. will likely have an “unusually and possibly exceptionally mild winter,” with temperatures as much as several degrees above normal.
On the coast, this means that more of the winter precipitation will fall as rain instead of snow, which could result in a reduced snowpack. In other parts of B.C., it could mean that there are fewer and less severe cold snaps.
Further, these mild temperatures will likely extend into spring — as far as May or early June — which could also result in an early snowmelt.
If there isn’t much spring and summer rainfall to make up for this, it could dry out the land and contribute to drought conditions, Merryfield explained.
Further, the El Niño could warm waters off B.C.’s coast by two degrees or more, drawing in marine species that usually inhabit waters much further south. In the past, Merryfield said that species of dolphins and semi-tropical fish that are found as far south as California are seen in B.C. waters.
And due to the shift in the trade winds, it suppresses the upwelling of nutrients that power a spring bloom of phytoplankton, or small plant organisms. The phytoplankton provide food for zooplankton, which are small animal organisms, and it carries on up through the food web.
“If there’s a deficiency in the nutrients and a reduced spring bloom — as that often happens during El Niño — there’s less food at the table for all of the marine species along the coast,” he said.