A vast dam across the Bering Strait could stop the AMOC collapsing

An ambitious engineering project could potentially see a dam built between Alaska and eastern Russia. This proposal aims to mitigate the severe impacts of a collapsing ocean current, a concept that was discussed at a recent major conference.

Jelle Soons and his colleague Henk Dijkstra from the University of Utrecht in the Netherlands are the minds behind this idea. They focus on the Atlantic Meridional Overturning Circulation (AMOC), a system which includes the Gulf Stream and significantly contributes to the moderate climate of northern Europe.

The AMOC, however, is weakening, and its potential collapse could drastically lower temperatures in northern Europe, according to some models.

Soons was inspired to consider a dam after learning about the Pliocene era, when lower sea levels created a land bridge at the current location of the Bering Strait, strengthening the AMOC. “I was like: ok, could we do this again?” he remarked.

To explore the dam’s impact, Soons and Dijkstra conducted simulations that varied the timing of the dam’s construction and the specific amount of freshwater involved.

Freshwater plays a crucial role as it currently flows from the Pacific through the Bering Strait into the north Atlantic, weakening the AMOC. A dam could halt or reduce this flow.

Previous studies by Soons and Dijkstra yielded mixed results: in some cases, the dam strengthened the AMOC, while in others, it weakened it. These findings stemmed from a basic, low-resolution model.

At the European Geosciences Union general assembly in Vienna on May 5th, Soons presented new research using a more advanced climate model on a supercomputer. This suggested that closing the Strait would bolster the AMOC, particularly if the dam were completed by 2050. “I was surprised at how strong the recovery was,” Soons noted.

The Bering Strait, only 59 meters deep at its deepest point, features two small islands in the center, making it feasible to construct a barrier in two sections. Ed McCann, a past president of the Institution of Civil Engineers, recommends using floating machinery to construct a barrier from rock and dredged sand, avoiding concrete. “This sort of construction is pretty simple, just very big and very expensive,” he wrote in an email.

Jonathan Rosser from the London School of Economics acknowledged the work’s interest but stressed the uncertainties involved, given the incomplete understanding of the AMOC. “These drastic things really do have big uncertainties attached,” he said.

Soons concurs, acknowledging that while the dam could benefit northern Europe, it might also create issues elsewhere, such as altering rainfall patterns. “Whether you would consider this a serious proposal? I don’t think we’re there yet,” he admitted.

This isn’t the first time researchers have considered a massive sea dam to address climate change. In 2020, Sjoerd Groeskamp from the Royal Netherlands Institute for Sea Research proposed the Northern European Enclosure Dam, which would involve building two barriers between the UK and Europe to protect low-lying areas from rising sea levels.

Beyond climate effects, such a dam could impact marine mammal migrations, tides, and shipping to remote communities. Soons has also contemplated alternatives like constructing half a barrier or a barrier that only descends to a depth of 10 meters. While these are “interesting ideas,” he has yet to fully assess their feasibility.