A Pacific marine heat wave has arrived in B.C. waters. Here's what it means for ocean life

A warm water mass heating up Pacific waters for months has arrived in B.C. — raising alarms about what impact those temperatures could have on marine life native to the coast.

The Pacific marine heat wave started forming about 1,600 kilometres off the coast in May, but in recent weeks has migrated west toward B.C. and Oregon. The warm water mass, about four million square kilometres in size, was predicted to wash up on B.C. shores by mid-August.

Over recent weeks, surface temperatures in the warm water mass have clocked in at up to five degrees higher than usual, prompting the U.S. National Oceanic and Atmospheric Administration to classify the heat wave as "extreme," the highest level of classification.

Marine heat waves can cause extreme weather, fuel rising sea levels, and contribute to faster-melting ice caps — all while threatening marine life.

Here's what you need to know about the one that has reached B.C. waters.

Marine heat waves are a common occurrence in the Pacific — but climate change is increasing their frequency and severity.

Pacific marine heat waves generally begin when summer temperatures spike and high Pacific winds slow, quickly heating up the surface temperature of the water.

The top layer of the ocean, which normally mixes easily with the cooler water underneath, becomes thinner, and in turn, is heated up more easily by the sun — and with those conditions, a marine heat wave is born.

The marine heat wave currently being documented in the Pacific isn't the only one scientists are watching.

Warm water masses have also been observed in the Gulf of Mexico, the Caribbean Sea, and the North Atlantic. Earlier this summer, the water temperature off the coast of Florida reached 37 C — hitting hot-tub levels of heat.

Researchers are also concerned about the sudden warm-up because oceans are crucial for the planet's ability to absorb and store heat.

Studies have estimated oceans have absorbed around 90 per cent of the excess energy and heat stored in the planet's climate system from greenhouse gas emissions over the last 50 years.

While warm waters may be welcomed by swimmers, they can prove dangerous for coastal ecosystems and the sea life accustomed to cooler temperatures.

Martin Haulena, head veterinarian with the Vancouver Aquarium, said the impact of the marine heat wave will be felt across the ecosystem — from kelp to shellfish, seabirds, and the larger marine mammals that populate B.C. waters.