Fierce. Treacherous. Beastly, perhaps.
Whatever you want to call it, the Saltstraumen strait, a 150-meter-wide channel in northern Norway, is considered the world’s strongest tidal current. Every six hours, as the tide fills up Skjerstad Fjord, an estimated 400 million cubic meters of water rush through at speeds reaching 20 knots.
Rowing the current, for those bold enough to try it, might feel like paddling against a horizontal waterfall, only with violent vortices and wild whirlpools trying to pull you under. Norwegian Olympic rowers Kjetil Borch and Nils Jakob Hoff went head-to-head with the Saltstraumen in 2016 using a carbon boat just slightly wider than a submarine sandwich. Somehow, they tackled the infamous strait, an achievement many thought was impossible.
Modern rowers, of course, aren’t the first to deal with angry ocean currents. The first humans to migrate from Asia to North America—had they arrived by boat—would have battled against ripping torrents along the western coast of Alaska.
“When the currents were at their strongest back then, you could have water flowing at two meters per second along the coastline,” said WHOI associate scientist Alan Condron, who studies links between climate and human migration using computer models. “You’d really struggle to paddle against that.”
Scientists have long hypothesized that ocean currents were actually weaker during the last glacial period due to lower sea levels. But Condron’s models, which take us back some 15,000-20,000 years ago before ancient Beringians crossed a land bridge connecting Siberia and western Alaska, found the opposite. According to the data, ocean currents could get pretty gnarly back then, and flowed faster than they do today. This was largely due to stronger winds that, in the simulated models, sped up currents and would have made boat travel a lot harder.
“Back then, the tropics were about the same temperatures as they are today, but the poles were a lot colder,” Condron said. “This wide temperature gradient created strong northward winds at a time when humans were trying to migrate south.”