Potential of Atlantic Ocean current collapse and its impacts on global climate

Even before Russia’s invasion of Ukraine in February 2022, energy prices were making headlines across Europe. Since the war started, however, discussions on the energy ecosystem in Europe intensified.

In October 2022, the Council of the European Union agreed to an emergency regulation to address high gas prices through new measures on joint gas purchasing, price limiting mechanisms, and transparent infrastructure use. Those measures, which were in effect through March 2023, reduced gas consumption by around 15% and decreased reliance on Russian supplies of pipeline gas from 40% down to 9%.

Even as gas and electricity markets stabilized, the European Commission and European Union members continued work to reduce Europe’s dependence on fossil fuels and accelerate the transition to green energy. The REPowerEU Plan, which supports projects in renewable energy, net-zero technologies, and workforce development, launched in May 2022 and received additional financing in July 2023.

Yet Europe’s efforts to establish a self-sustainable energy sector may face complications from another threat that might occur sooner than previously theorized—collapse of the Atlantic meridional overturning circulation (AMOC).

The AMOC is a system of surface-level and deep currents in the Atlantic Ocean. This system helps regulate global and regional climate by carrying warm, salty surface waters up north and colder, deep waters back down south.

Changes in temperature and salinity affect the flow of AMOC currents, and multiple studies have found that the AMOC’s flow has slowed considerably in recent decades. While this weakening is driven partly by natural variations in the Earth’s climate system, human-caused climate change is also a significant factor. Specifically, the melting Greenland ice sheet is introducing an influx of cold, fresh water into the sea that destabilizes the well-defined temperature–density gradients essential to the AMOC’s flow.

Over large timescales, the AMOC naturally switches between a strong, fast circulation and a much weaker, slower circulation. However, scientists are concerned that because of the additional temperature and salinity changes resulting from human-caused climate change, the AMOC may cease functioning altogether rather than just slowing down.

A 2019 report by the United Nations Intergovernmental Panel on Climate Change (IPCC) concluded a full collapse of the AMOC would be unlikely this century and generally downplayed disaster scenarios. But debate around the AMOC’s potential collapse was reinvigorated last summer when Peter and Susanne Ditlevsen, professors in physics and statistics, respectively, at the University of Copenhagen in Denmark, published an open-access paper in July 2023 suggesting a high likelihood of AMOC collapse between 2025–2095, with a central estimate of 2057.

The Ditlevsens reached this conclusion using a new model that most experts agree is mathematically rigorous and internally consistent. However, many in the scientific community questioned the model’s 95% confidence interval.

The model relies on observations of sea surface temperatures from one region in the North Atlantic to extrapolate the future of the entire ocean system. The assumption that these observations can represent the whole system “needs to be further tested,” says Levke Caesar, an AMOC expert at the University of Bremen in Germany, in a Scientific American article.

Despite these critiques, other studies published in 2021 and 2022 confirm that the AMOC may be approaching a tipping point sooner than the IPCC’s prediction. And if collapse does occur, it would have widespread global consequences, as described in the Scientific American article.

For example, parts of Europe could experience significant cooling by as much as 5 or 10 degrees Celsius. Meanwhile, tropical rain belts might shift their positions, causing drought in some regions but flooding in others.

Additionally, if the AMOC can no longer ferry large volumes of water around the world, the ocean may absorb less carbon dioxide from the atmosphere. Plus, parts of the deep ocean may receive less oxygen.

Knowing these potential ramifications, “I think this risk should be taken very seriously,” writes Stefan Rahmstorf, an ocean expert at the Potsdam Institute for Climate Impact Research in Germany, in a RealClimate blog post.

Finnish startup scales sand battery technology to the next level

Two years ago, in August 2022, the Bulletin reported on the development of a novel sand-based heat storage system by Finnish startup Polar Night Energy. Now, two years later, the company has taken several steps toward widespread commercialization of this technology.

In Polar Night Energy’s “sand battery” system, electricity generated from solar and wind power is passed through an array of electric resistive heating elements, heating the air around it. This hot air is circulated through a network of pipes inside an insulated sand-filled steel tank, which warms the sand up to about 500°C (932°F). The air then flows back out of the tank into a heat exchanger, where it heats water that is then circulated through building heating systems.

In July 2022, the first commercial installation of Polar Night Energy’s sand battery system took place in the town of Kankaanpää, Finland. Now, in March 2024, Polar Night Energy entered into an agreement with Finnish district heating company Loviisan Lämpö to build an industrial-scale system in Pornainen for Loviisan Lämpö’s district heating network.

The new system will be about 10 times larger than the one in operation in Kankaanpää, with a thermal energy storage capacity of 100 MWh. This capacity equates to almost one month’s heat demand in summer and a one-week demand in winter.

Unlike the system in Kankaanpää, the sand battery in Pornainen will use crushed soapstone as the thermal storage medium. This material is a byproduct from the manufacture of heat-retaining fireplaces by Tulikivi, Finland’s largest stone processor and the world’s largest manufacturer of heat-retaining masonry heaters.

In a press release, Tulikivi CEO Heikki Vauhkonen says, “This collaboration supports Tulikivi’s goals of maximizing the utilization of raw materials.”

Construction and testing of the system, which will measure 13 meters high by 15 meters wide, is estimated to take around 13 months. As such, it should be ready to keep residents warm by 2025.

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