Tag Archives: AMOC

AMOC: An Ambitious Strategy to Preserve Vital Ocean Currents Using Giant Parachutes

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Strategies to uphold the current involve oversized versions of parachute-like ocean anchors

Ed Darnen (2.0 by CC)

As part of an ambitious initiative to avert severe climate change, large parachutes could be deployed into Atlantic waters using transport tankers, drones, and fishing vessels.

The Atlantic Meridional Overturning Circulation (AMOC) moves warm water from the tropics northward and helps stabilize temperatures in Northern Europe.

Nevertheless, the swift melting of Arctic ice and rising sea temperatures have hampered these currents, prompting some scientists to warn that they could falter entirely within this century. Such an event would disrupt marine ecosystems and exacerbate the cooling of the European climate.

Experts emphasize the urgent need to cut greenhouse gas emissions to mitigate the risk of AMOC collapse and other catastrophic climate “tipping points.” However, some are exploring alternative, more fundamental methods to preserve the current.

Stuart Haszeldine from the University of Edinburgh, along with David Sevier, introduced a concept from the British water treatment firm Strengite during a recent meeting in Cambridge, UK. They propose utilizing just 35 ocean tugs, each capable of pulling underwater parachutes roughly half the size of a soccer pitch, which could effectively move enough water to maintain the current. “A modest amount of energy and equipment can yield a significant impact,” Haszeldine remarks.

These parachutes, designed similarly to existing ocean anchors, stabilize containers in rough weather while also aiding in water movement across the sea surface. Each parachute features a central hole 12 meters wide to allow marine creatures to escape.

The operation would run 365 days a year in a rotating schedule, using drones, transport tankers, tugs, or wind kits. “It’s a small but consistent intervention,” notes Haszeldine.

Sevier refers to this proposal as “any Mary,” indicating a solution to stave off the severe consequences of AMOC collapse. “This is about buying time,” he asserts, emphasizing the need for the world to reduce emissions sufficiently to stabilize global temperatures at safe levels.

However, leading AMOC researchers express skepticism about the idea. Rene van Westen from the University of Utrecht, Netherlands, highlights that the density differences between cold, salty water and warm, fresh water play a crucial role in the descent and upwelling movements that sustain AMOC.

“If this idea is to work,” Van Westen argues, “you can only use surface wind to influence the top layer of water.

Stephen Rahmstoef from the Potsdam Institute for Climate Impact Research concurs. “The challenge lies not in moving surface water horizontally but in sinking it to depths of 2,000 to 3,000 meters and returning it south as a cold, deep current,” he states.

Meric Srokosz of the UK National Oceanography Centre believes the proposal is “unlikely to succeed,” given the variable weather conditions that complicate equipment deployment in the oceans.

Haszeldine welcomes feedback from fellow scientists regarding the proposal and hopes it will inspire ocean and climate modelers to assess the ecological and environmental ramifications of the plan. “I believe this warrants further investigation,” he asserts.

More generally, Haszeldine argues for increased research focused on climate intervention strategies to sustain ocean circulation: “I don’t see anyone else working on ocean currents.”

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Source: www.newscientist.com

AMOC: Crucial ocean currents are unlikely to shut down completely by the end of the century

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AMOC brings warm water north from the tropical region near the surface and takes cold water in opposite directions of the deep sea

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Important ocean currents will rarely close by the end of this century, according to new findings that undermine the end of the impending catastrophic collapse.

The Atlantic Meridian Surrounding Circulation (AMOC) transports warm water from the tropical north and helps maintain temperatures in Northern Europe. The temperature and the influx of cold water from the Arctic ice weakens the current temperature, and scientists fear it can stop it completely. This will disrupt marine ecosystems and cool the European climate a few degrees faster.

Some researchers say that the irreversible closure of AMOC could be in the century. But I say this worst-case scenario is unlikely Jonathan Baker At the Met Office in the UK.

To investigate whether a complete AMOC collapse of this century is possible, Baker and his colleagues used 34 climate models to simulate changes in AMOC under extreme climate change, and greenhouse gas levels trained overnight from today's levels. The team also modeled a large amount of freshwater entering the North Atlantic at many times the rate of ice melting now.

They found that although AMOC is significantly weakened in these two scenarios, ocean currents continue in their weakened state, supported by deep-sea upwellings in the North Atlantic, driven by southern sea winds. “The Southern Ocean winds continue to blow, and this brings deep waters up to the surface. This works like a powerful pump,” Baker says. “This keeps AMOC running on models of this century.”

This finding helps explain why climate models generally simulate more stable AMOCs in the warming world compared to studies that rely on statistical methods. This tends to suggest that AMOC is more vulnerable.

Niklas Bore The Potsdam Climate Impact Institute in Germany said the findings are “good news” for those worried about the imminent collapse of the AMOC. “I agree that all cutting-edge climate models will not show a complete AMOC collapse within the 21st century.

However, the model does not predict a complete collapse of AMOC, but shows that quaternary reddish CO2 concentrations lead to a 20-81% reduction in the current intensity.

With AMOC weaker by about 50%, the impact on climate will become important, Baker says it will be important due to marine ecosystem disruption, sea level rise on the North Atlantic coastline, and changes in global rainfall patterns that affect crop harvests around the world. However, this type of weakening does not bring rapid cooling to Europe, he says.

In comparison, Bohr emphasizes that AMOC, which is 80% less than today, will have a devastating effect. “Of course, it's a nearly blocked AMOC,” he says. “It has all the impact on Europe's cooling and changing patterns of tropical monsoon, and all the things we are concerned about.”

Stephen RahmstoefHe is also at the Potsdam Institute for Climate Impact in Germany, and agrees that under the extreme warming of this century, there may be a weak and shallow AMOC trend left in the world. Some studies even define AMOC disintegration as this type of substantial weakening, he says. “A new study is investigating the remaining wind-driven covers [current] In more detail, this is a valuable contribution to the scientific literature,” he says. “However, in response to human-induced global warming, we will not change our assessment of the risks and impacts of future AMOC changes.”

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Source: www.newscientist.com

The Possible Collapse of AMOC: Simulations Highlight Real Danger of Stopping Atlantic Currents

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Ocean currents flowing from the tropics to the North Atlantic have a major influence on Europe's climate.

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As the planet warms, is there a serious risk that the Atlantic Current that warms Europe will slow down and stop? Yes, according to the most detailed computer simulation ever performed. The likelihood of this scenario remains highly uncertain.

“We have demonstrated that it is indeed possible with our current setup,” he says. René van Westen At Utrecht University in the Netherlands.

Now, warm water, made more salty by evaporation, flows north from the tropics along the surface of the Atlantic Ocean, keeping Europe much warmer than it would otherwise be. When this water cools, it sinks because it becomes more salty and denser. It then returns to the tropics and flows along the ocean floor into the southern hemisphere.

This is known as the Atlantic Meridional Overturning Circulation (AMOC). Studies of past climate suggest that the dramatic cooling episodes that have occurred around Europe over the past 100,000 years or so have been associated with so-called tipping points, when reverse currents slow down or stop completely, and small changes in may convert one system to another. state.

The cause is thought to be melting ice sheets. The influx of large amounts of fresh water into the North Atlantic reduces salinity, which in turn reduces surface water density and reduces the amount of water that sinks.

However, this has proven difficult to model. Most shutdown simulations require adding unrealistically large amounts of fresh water at once. Some also question whether this is a potential tipping point, since recent simulations using more advanced models have not shown any shutdowns.

Now, van Westen's team has run the most sophisticated simulation to date, which took a total of six months to run on the Dutch state-run supercomputer Sunellius. It was very expensive, he says.

Unlike previous simulations, the team added fresh water gradually rather than all at once. This created a positive feedback that amplified the effect. The decrease in salinity reduced the amount of water sinking, which reduced the amount of brine flowing north, further reducing salinity.

This eventually broke the overturning circulation, causing temperatures to rise in the Southern Hemisphere but plummet in Europe. For example, in this model, London would be 10°C (18°F) cooler on average, and Bergen, Norway would be 15°C (27°F) cooler on average. Other impacts include localized sea level rise in areas such as the East Coast of the United States.

Additionally, some of the changes seen in the model before the collapse are consistent with changes seen in the real Atlantic Ocean in recent decades.

But to cause this collapse, the researchers had to run the model for 2,500 years. And they needed to add huge amounts of fresh water. Although less than previous simulations, it is still about 80 times the amount that is currently flowing into the ocean from the melting Greenland ice sheet. “So it's absurd and not very realistic,” Van Westen said.

Furthermore, this simulation did not include global warming. The team now plans to rerun the simulation with that in mind.

“This is the most cutting-edge model in which such experiments have been performed,” he says. Peter Ditlefsen He is a co-author of a 2023 study predicting that the Atlantic overturning current could break up between 2025 and 2095, based on changes in sea surface temperatures.

The model suggests it will take large amounts of fresh water and centuries to stop the circulation from reversing, but why do we think climate models are underestimating the risk of nonlinear changes like the Atlantic tipping point? There are several, Ditlefsen said.

Climate models need to divide the world into large cubes to make their calculations workable, he says, and this has a smoothing effect. Additionally, the model has been calibrated based on how well it simulates the 20th century climate, although there was a linear relationship between greenhouse gas emissions and the resulting changes. may not be applicable in the future.

“We should expect the model to be less sensitive than the real world,” Ditlevsen says.

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Source: www.newscientist.com