Building a giant dam between Russia and Alaska could save Atlantic flow, which is important for regulating northern Europe’s climate. But that massive undertaking comes with other risks, researchers explain in a new study.
By cutting the Pacific Ocean and the Arctic Ocean across the Bering Strait, the giant geoengineering project could buy more time for the threatened conveyor belt of ocean currents known as the Atlantic Meridional Overturning Circulation (AMOC), the study says. However, the study authors and other researchers cautioned that effectiveness is variable, the results are preliminary, and further modeling studies are needed to see if such a bold course of action is worth it.
AMOC impending collapse
The AMOC moves warm salt water from the tropics north, where it cools and sinks, and moves the cold water south, sustaining marine life and regulating the climate across Europe, Africa, and the Americas. This is why Europe maintains a relatively mild climate despite its high latitude.
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Many studies suggest that AMOC is weakening and may collapse. A study published earlier this month found that the economy is expected to slow by between 43% and 59% by 2100, a 60% stronger slowdown than previous models predicted, and could be closer to collapse than previously thought. If it fails, the consequences could be catastrophic, causing temperatures to plummet in northern Europe and triggering droughts, sea levels to rise by at least 50 centimeters along the northeastern coast of North America, and potentially disrupting food production.
“The evidence points to collapse, but it is very uncertain,” lead author Jere Souns, a researcher who studies AMOC at the Institute of Oceanic and Atmospheric Research at Utrecht University in the Netherlands, told Live Science.
There are two ways global warming could stop AMOC. One possibility is that the warm waters of the North Atlantic could prevent the warm, salty water it carries from cooling and sinking. Another is that melting of the northern ice sheets could add more fresh water to the mix, making the arriving water less salty and halting subsidence.
Previous studies have shown that the AMOC was stronger during the mid-Pliocene, about 3 million years ago, largely because of the presence of a land bridge blocking the Bering Strait. “So we wondered what would happen if we closed the Bering Strait again,” Soon said.
Three dams across the strait
In a new study published Friday (April 24) in the journal Science Advances, Sounes and his colleague Henk Dijkstra, a physical oceanographer at the Oceanic and Atmospheric Institute, modeled what would happen if that passage were closed. First, there are two islands in the middle of the strait, which would require three dams to cover the 51-mile (82-kilometer) wide area. The longest one would need to be about 24 miles (38 km) long.
Researchers found that by reducing carbon dioxide (CO2) emissions and weakening the AMOC slightly, the closure of the Bering Strait could strengthen the AMOC and allow it to continue functioning even as CO2 emissions increase. However, they also found that a blockade of the Bering Strait would accelerate the weakening of the AMOC, since it is much weaker.
“This means there is no simple solution,” Jonathan Baker, a marine scientist at the Met Office who was not involved in the study, told Live Science in an email. This means that dams can only postpone AMOC collapse in certain circumstances, he added.
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The findings are very interesting and offer an alternative way to mitigate the effects of rising CO2 levels, said Aixue Hu, an oceanographer at the National Center for Atmospheric Research who was not involved in the study.
“However, the overall effect is inconsistent and highly dependent on AMOC strength and CO2 levels,” Hu told Live Science via email. “Even if the closure of the Bering Strait strengthens the AMOC and allows for more CO2 emissions in the near future, the long-term effects are still uncertain.”
Soons said building the Bering Strait dam should be technically feasible. The longer section would not be much longer than the 20-mile (32-kilometer) Ahu Dam in the Netherlands or the 21-mile (33-kilometer) Saemangeum Seawall in South Korea, he said. Bering Strait Dam has a maximum depth of 194 feet (59 meters), which is not much deeper than the deepest part of the Saemangeum Seawall, which is 177 feet (54 meters) deep.
However, both of these constructions are in relatively calm coastal waters, not in remote areas with strong ocean currents and sea ice, or with opposing geopolitical forces.
Separating the Pacific-Arctic link would also impact wildlife, fishing, shipping and indigenous communities that depend on the strait for food and trade, Soon said.
“Closing the strait would alter the exchange of water, heat, nutrients and marine life between the Pacific and Arctic Oceans, with potential impacts on marine ecosystems and regional ocean circulation,” Baker said. “It also has the potential to trigger climate change, which is not yet fully understood. Interventions of this scale will require careful consideration of the intended benefits as well as potential unintended consequences.”
Soon, Baker and Hu both said more modeling work was needed to examine their findings and get a more detailed picture of what would happen in different scenarios.
There is also an easier way to save AMOC. “Closing the Bering Strait may delay collapse in some circumstances, but it does not eliminate the fundamental risks of continued warming,” Baker said. “The most reliable way to reduce AMOC risk remains to reduce greenhouse gas emissions.”
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