The Atlantification of the Arctic Ocean Is Underway

This story originally appeared in Hakai Magazine and is part of the Climate Desk collaboration.

In the Fram Strait off Greenland’s west coast, Véronique Merten encountered the foot soldiers of an invasion.

Merten was studying the region’s biodiversity using environmental DNA, a method that allows scientists to figure out which species are living nearby by sampling the tiny pieces of genetic material they shed, like scales, skin, and poop. And here, in a stretch of the Arctic Ocean 400 kilometers north of where they’d ever been seen before: capelin.

And they were everywhere.

The small baitfish found in the northern Atlantic and Pacific Oceans is an ardent colonizer. Whenever the ocean conditions change, it’s really easy for capelin to expand their range, says Merten, a marine ecologist at the GEOMAR Helmholtz Centre for Ocean Research Kiel in Germany.

It is difficult to estimate an animal’s abundance based solely on the amount of its DNA in the water. Yet in Merten’s samples, capelin was the most frequently encountered species—far more than typical Arctic fish like…