Climate & Weather
Paddling an angry, ancient ocean
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.”
The models also show that currents were further accelerated by massive floods of glacial meltwater that periodically drained into the ocean from the modern-day Columbia River. As the edges of the Cordilleran ice sheet retreated, these meltwater floods would inundate the Pacific Ocean and stay trapped along the coastline due to the Earth’s rotation. That, combined with wind-driven chop and icebergs calved from the Cordilleran Ice sheet, would have slowed things down further.
“No one wants to be canoeing in a sea of filled with giant icebergs and strong currents that are moving in the opposite direction to where they want to go,” Condron said.
It sounds like a lot of work. But sometimes paddling along Alaska’s ancient western coast may not have been quite as challenging. Condron’s models show a number of “benign” periods when the currents had quelled and the winds had subsided.
And, there may have been alternatives to boat travel when the winds and currents were too much. Beringians may have sledded over sea ice for parts of the southward migration, much like modern-day Inuit people do when hunting. Or, they may have simply walked south along the coast. But with large glaciers extending into the ocean and blocking coastal routes, even this may have been a tough way to get around.
“We still have much to learn about early human migration into North America, but put simply, it would have been very challenging, even at the best of times,” said Condron.
Funding for this research was provided by The Harris Family Fellowship (25620800) WHOI IR&D: The Impact of Pacific Megafloods and Siku Events on Climate.
MEET THE AUTHOR Evan Lubofsky
Evan Lubofsky is a science writer and editor at Woods Hole Oceanographic Institution. Read more
