Tag Archives: AMOC

AMOC Current Collapse: Signs It May Already Be Happening

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Atlantic Ocean Currents Visualization

Visualization of Atlantic Currents Based on Sea Surface Temperature Data

NASA/Goddard Space Flight Center Scientific Visualization Studio

Research indicates that a potentially disastrous collapse of the Atlantic Current—a crucial climate regulator for Europe—may be inevitable. Model forecasts suggest a 10 to 23 percent chance of this collapse becoming permanent.

“We are already on the brink of collapse, and even now, nothing can alter that,” states Phil Holden from the Open University, UK.

The Atlantic Meridional Overturning Circulation (AMOC) is vital for transporting warm, salty waters from the tropics to the North Atlantic. Here, the water cools, sinks, and travels south, regulating climate across Europe, Africa, and the Americas.

Recent observations reveal signs of weakening in this critical system, particularly a slowdown in specific regions. Factors such as Greenland melting and climate change are contributing, resulting in less dense saltwater that hampers the rate of subsidence.

Scientists warn that if AMOC collapses, Europe may face near-Arctic conditions, while global monsoon systems could weaken. A recent study suggests AMOC may reach a tipping point within a few decades, although estimating the likelihood remains challenging.

“Currently, the collapse of AMOC is somewhat invisible,” Holden remarked. “We lack clear predictions concerning the timing and quantification of such events.”

“There are abundant uncertainties and differing views within the scientific community,” adds Tim Renton from the University of Exeter, UK.

To enhance understanding of the AMOC’s dynamics, Holden, Renton, and their colleagues conducted 21 computer simulations from 2005 to 2135, varying rates of Greenland ice melt and peak emissions. The team anticipates that greenhouse gas emissions will decline to net zero over 35 years post-peak, with a consistent rate of ice melt.

Under conservative scenarios predicting peak emissions by 2025 and only 54 millimeters of sea-level rise from the Greenland ice sheet by 2100, there is already a 10 percent chance of AMOC collapse. This is defined as a circulation that occurs solely at lower latitudes, with reversed currents ceasing to deliver heat to higher latitudes.

Models predict that failing to commence a net-zero trajectory by 2100 could escalate the collapse probability to 80 percent.

Conversely, melting Greenland ice may raise sea-level rise predictions to 274 mm by 2100, which could increase the collapse probability to 23 percent.

Even with an inevitable collapse, it will take considerable time. Simulations show the average delay from the onset of collapse to its manifestation is about 84 years, with the earliest occurrence around 2060.

Tackling the notion of a “committed collapse,” Up to Wagner views this framing as useful for risk management. Yet, applying this to reality is complex. “There’s strong evidence of weakening, yet major mechanical consequences remain uncertain,” he cautioned.

According to Jonathan Baker from the UK’s Met Office, the simulation offers valuable insights into AMOC’s response to various conditions. However, the model’s lower resolution may affect risk estimates compared to other high-resolution climate models.

While state-of-the-art climate models operate on a 1° grid, extensive computations are required for long-term simulations. The chosen model for this study uses a 5° grid, a strategic decision due to computational limitations.

“Previous technology didn’t allow for high-resolution models,” Renton explained. Although lower resolution raises risk estimates, recent research indicates that higher resolutions may increase, rather than diminish, the estimates.

“Further investigations employing various climate models alongside broader evidence are crucial before drawing solid conclusions about potential AMOC collapse risks,” Baker emphasized.

If the world is progressing toward AMOC collapse, as modeled, it underscores the urgent need for emission reductions. Renton asserts that delaying net-zero commitments will significantly raise the probability of collapse. A ten-year delay may lead to an average collapse timeframe of 57 years instead of 84 years.

“What this model conveys is a pressing need to accelerate our journey to net-zero emissions and maintain the collapse risk at 10%,” Renton urged.

This aligns with recent studies indicating that AMOC’s slowdown could be reversed if carbon emissions are effectively reduced.

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Source: www.newscientist.com

Is the AMOC Current Slowdown Gradual and Reversible? Insights and Implications

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Visualization of Atlantic Ocean Flows from Satellite Images

Carsten Schneider/Science Photo Library

The Atlantic Meridional Overturning Circulation (AMOC) may face weakening due to freshwater influx from Greenland’s snowmelt. However, cutting-edge climate models indicate this slowdown is likely to be gradual and reversible if global warming is curbed.

AMOC is a critical ocean current system that conveys warm, salty water from the tropics to the North Atlantic. There, it cools, sinks, and circulates back southward along the ocean floor. The influx of fresh meltwater from Greenland’s ice sheet appears to be mixing with denser seawater, slowing its downward flow.

<p>Recent estimates indicate Greenland is losing approximately <a href="https://www.nature.com/articles/s41586-023-06863-2">30 million tons of ice</a>. Some experts express concerns that AMOC could undergo a sudden and irreversible collapse, potentially plunging Europe into near-Arctic conditions. One <a href="https://iopscience.iop.org/article/10.1088/1748-9326/adfa3b">study</a> suggests that AMOC might cross a crucial tipping point within decades.</p>
<p>However, modeling by <a href="https://research-portal.uu.nl/en/persons/oliver-mehling/">Oliver Mehring</a> and colleagues at Utrecht University revealed that while AMOC may weaken steadily under ongoing global warming, it is unlikely to reach a point of no return solely due to Greenland’s snowmelt.</p>
<p>“The prevailing notion that melting from the Greenland ice sheet could trigger an irreversible AMOC collapse is a significant oversimplification,” stated Mehring. “The snowmelt from Greenland alone is insufficient to push AMOC past its tipping point.”</p>

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<p>It is believed that atmospheric warming not only accelerates Greenland's melting but also directly undermines the AMOC by preventing brine in the North Atlantic from cooling adequately. This warming allows the ocean to hold more freshwater, which ultimately leads to increased rainfall, diluting saltwater, and reducing ocean mixing. This combination of warming and freshwater influx diminishes the sinking action crucial to AMOC.</p>

<p>While most predictive models of future climate change concentrate on atmospheric warming's impact on AMOC, <a href="https://research-portal.uu.nl/en/persons/oliver-mehling/">Mehring</a> and his team found that atmospheric warming could weaken AMOC by a staggering 60% by 2300. If the volume of Greenlandic snowmelt were to increase, the AMOC's strength could diminish by an additional 20%.</p>

<p>Nonetheless, their research indicates that if atmospheric CO2 levels were to decrease by 1% annually starting in 2250, AMOC could fully recover by around 2400. Although these models are not designed to predict the exact timeline or extent of AMOC changes, they imply that increased freshwater input from Greenland won't lead the AMOC over the tipping point.</p>

<p>A reduction of 80% in AMOC could still lead to crop failures in Western Europe, ice formation in the North Sea, and disruption of tropical monsoon patterns. Fortunately, the study indicates that such declines would be gradual, predictable, and reversible if humanity ceases fossil fuel combustion. As <a href="https://www.bas.ac.uk/profile/lsim/">Louise Sim</a> from the British Antarctic Survey commented, "While scenarios of AMOC crashing are conceivable, they are unlikely to occur. Instead, AMOC shows a strong linear relationship with cumulative CO2 emissions."</p>

<p>Despite these findings, the possibility of a tipping point cannot be completely dismissed. Previous research conducted by <a href="https://www.uu.nl/staff/RMvanWesten">René van Westen</a> and colleagues at Utrecht University, using a different model, suggested that significant melting from Greenland could lead to AMOC's irreversible collapse. However, this model applied meltwater at a constant rate rather than simulating the gradual increases observed in reality.</p>

<p>“Other climate models have predicted crossings of the tipping point under 21st-century climate change, illustrating that results can be model-dependent,” van Westen remarked.</p>

<p>In addition to Greenland’s melting, several other climate changes pose risks to the AMOC. For instance, freshwater from Antarctic snowmelt could disrupt global circulation dynamics, of which AMOC is a vital component. However, the impacts remain uncertain; depending on the timing of Antarctic melt, it could also help sustain the AMOC.</p>

<p>This new study does not eliminate the risk of an AMOC tipping point but contributes valuable insights to the ongoing climate discussion, highlighted <a href="https://scholar.google.com/citations?user=Cn7wuysAAAAJ&amp;hl=en">Jonathan Baker</a> from the UK’s Met Office.</p>

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Source: www.newscientist.com

Impact of U.S. Ocean Program Budget Cuts on El Niño and AMOC Monitoring

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One of the Ocean Observations Initiative’s moored spheres being lifted out of the ocean.

Credit: Rebecca Travis / Woods Hole Oceanographic Institution

During the winter of 2013-2014, shifts in the jet stream led to the emergence of a significant warm water mass dubbed the “blob,” which extended over 1,500 kilometers across the North Pacific Ocean. This phenomenon was detected by floating instruments anchored to the ocean floor off the coastlines of Alaska, Washington, and Oregon, alerting scientists and the fishing industry to water temperatures exceeding normal levels by up to 4 degrees Celsius.

These instruments are part of the Ocean Observing Initiative (OOI), which comprised five moorings along the West coast of the United States, as well as off the East coast and in Greenland. The National Science Foundation (NSF) announced a substantial $220 million investment in 2023, emphasizing the necessity of the OOI for monitoring “Earth’s vital organs.” However, recent announcements from the NSF indicated plans to dismantle most of these arrays due to funding reductions initiated by the previous administration.

Between 2015 and 2016, sensors attached to the OOI mooring wire identified the warm water mass, with temperatures rising significantly influenced by global-warming events, particularly El Niño. This data revealed that occurrences of the blob happened again in 2019 and may be becoming more frequent due to climate change, which has been associated with toxic algae blooms affecting fisheries, such as the $60 million loss from California’s Dungeness crab fishery.

The removal of OOI moorings jeopardizes not only weather forecasts, including precipitation predictions which affect drought conditions in the western U.S., but also the ability to monitor key elements like the Atlantic Meridional Circulation (AMOC), crucial for maintaining Europe’s temperate climate and assessing El Niño impacts.

“We’re flying blind, which ultimately results in greater costs,” states John Abraham from the University of St. Thomas in Minnesota. Operating the OOI costs approximately $56 million annually, while U.S. commercial fisheries, relying heavily on OOI data, generate billions of dollars annually. Weather-related disasters have historically caused damages reaching $183 billion, further emphasizing the importance of accurate data.

Without access to the OOI data, fishing fleets will struggle to determine which areas will be less affected by El Niño events. This upcoming El Niño is predicted by some models to be among the strongest on record. Oyster, clam, and shellfish farms would find it challenging to prepare for diminished temperatures and nutrients caused by El Niño, while scientists would lose sight of significant impacts on marine ecosystems, including the formation of low-oxygen “dead zones.”

“The timing couldn’t be worse,” lamented Hilary Palewski from Boston University, stressing the critical function of OOI in marine research.

Satellites cannot penetrate the ocean’s surface, making data from submerged floats, gliders, and tethered vessels vital for understanding the Earth’s ocean-covered regions, which account for about 70%. These instruments primarily measure temperature, salinity, and flow, but the OOI moorings also assess pH, oxygen, and CO2 levels—essential for comprehending oceanic biology and chemistry, particularly in remote, monitored regions where water mass movements influence climate.

The loss of these sensor networks will also pose challenges globally, especially concerning AMOC observability. The OOI array located in the Irminger Sea, east of Greenland, is part of the OSNAP initiative—a network of gliders and moorings stretching from Canada to Scotland, monitoring the warm saltwater flow, pivotal for the AMOC. A breakdown in this system could result in Europe experiencing severe winter conditions and disrupt essential monsoon rains vital for agriculture in Africa and Asia.

“OSNAP has revealed that most actual capsize events occur east of Greenland, making the Irminger Sea crucial for understanding variability,” notes Femke de Jong from the Royal Netherlands Marine Institute.

Palewski added that dismantling OOI will leave a significant data gap that could hinder future understanding of the AMOC, even if replacement is pursued later.

Scientists are concerned that the dismantling of OOI may herald a drastic reduction in U.S. ocean research funding, risking initiatives like OSNAP and potentially jeopardizing the Argo project, which comprises around 4,000 drifting instrument floats, over half of which are managed by the U.S.

In a statement to New Scientist, the NSF mentioned that the OOI’s removal is aimed at “prioritizing support for evolving scientific priorities.” However, this is contingent on political agendas, with experts like Gretchen Goldman of the Union of Concerned Scientists condemning it as an “attack on science,” amid proposals to cut thousands of research grants and reduce the NSF budget significantly.

This week, new regulations proposed by the administration seek to eliminate peer reviews for research funding applications and empower political appointees rather than independent experts to determine the fate of federally funded studies. Additionally, bans on international cooperation and studies on gender and diversity are planned.

Edward Deaver, a professor at Oregon State University managing the OOI array, emphasizes that both the dismantling of OOI and the proposed grant rule changes constitute sweeping reforms that threaten to undermine peer review and politicize NSF-funded research.

A recent study indicated that dismantling even a fraction of the Global Ocean Observing System, which includes the OOI and Argo floats, could inflate errors in annual ocean heating rates by 33%. This is akin to predicting an unemployment rate of 3% with an imprecise range of 2% to 4%, according to Abraham, a member of the research team.

“This is a calculated move to silence our monitoring of the ocean,” he asserts regarding the OOI dismantling. “If we don’t measure, how can we identify problems?”

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Source: www.newscientist.com

Mysterious Cold Mass in Atlantic Signals Potential Weakening of AMOC

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The “Cold Blob” in Temperature Visualization

Credit: NASA Scientific Visualization Studio/Goddard Space Flight Center

The Earth’s surface has experienced warming over the past 150 years, with the exception of certain areas in the North Atlantic Ocean. This specific region, found southeast of Greenland, has been termed the “warming hole” or “cold mass,” indicating it is up to 1°C cooler than historical averages.

There is ongoing debate among scientists regarding the reason for the existence of this cold blob. Recent studies suggest it may be linked to the weakening of the Atlantic Meridional Circulation (AMOC), a crucial ocean current that distributes warmth from the tropics to Europe.

<p>The AMOC is responsible for transporting warm, salty water from the Gulf of Mexico to the North Atlantic, where it cools, sinks, and then returns south along the ocean floor. Scientists are concerned that an influx of freshwater from melting ice in Greenland could lower the salinity in this area, potentially slowing the sinking process and weakening the overall circulation.</p>
<p>Recent research indicates that the AMOC may <a href="https://iopscience.iop.org/article/10.1088/1748-9326/adfa3b">cross a tipping point</a> in the coming decades, potentially leading to a complete collapse. This collapse could have severe consequences, causing significant cooling in Europe and disrupting critical monsoon rains vital for agriculture in Africa and Asia. However, current direct observations of AMOC strength span only 22 years, which is insufficient to establish clear trends.</p>
<p>Climate <a href="https://www.nature.com/articles/s41586-018-0006-5">modeling</a> suggests that the slowing AMOC reduces the supply of warm water to the North Atlantic, thereby creating this cold mass. Other models, however, attribute a major portion of the phenomenon to atmospheric changes.</p>
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<p>A <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2022GL100420">2022 study</a> by <a href="https://cos.northeastern.edu/people/chengfei-he/">He Chengfei</a> and researchers from Northeastern University, Boston, found that accelerated warming in the Arctic is diminishing the temperature disparity between the polar regions and tropics. This shift is causing the jet stream to move northward into the cold mass area, resulting in stronger westerly winds that increase evaporation, drawing heat away from the ocean.</p>
<p>As evaporation intensifies, cloud cover also increases. Some research indicates that this cloud cover may further contribute to the cooling of the blob.</p>

<p>Research led by <a href="https://www.pik-potsdam.de/members/stefan/homepage">Stefan Rahmstorf</a> at the Potsdam Institute for Climate Impact Research is closely examining the cold mass through climate reanalysis, utilizing direct weather observations from satellites, buoys, and ships, rather than relying on modeling techniques.</p>
<p>Since 1955, they have discovered that heat loss from the ocean’s surface has diminished in the cold mass area. It appears that the ocean is cooling not just at the surface but also at depths of up to 1,000 meters. This indicates that the AMOC is transporting less heat rather than the atmosphere removing more heat.</p>
<p>According to Rahmstorf, “Wind and clouds can only account for a minor portion of the warming hole. While some models suggest atmospheric influences, the data indicates that oceanic factors are the primary causes.”</p>
<p>This finding highlights that the Atlantic circulation has been undergoing changes for decades, intensifying concerns regarding the potential collapse of not only the AMOC but also the surrounding subpolar circulation, which is vital to the process. If this circulation were to shut down, <a href="https://nyaspubs.onlinelibrary.wiley.com/doi/abs/10.1111/nyas.14659">the UK and neighboring regions may experience even more rapid temperature drops</a> than a full AMOC collapse.</p>
<p>Rahmstorf warns, “The subarctic circulation reaching a tipping point could lead to severe climate impacts in Western Europe as early as the 2040s.”</p>

<p>However, direct measurements of ocean surface heat fluxes are currently lacking, making it challenging to accurately estimate them through modeling. A 2021 study, which used data from Rahmstorf's research, found that winds <a href="https://link.springer.com/article/10.1007/s00382-021-06003-4">may account for the majority</a> of the cold blob's formation.</p>
<p>According to He, “Inferring the energy budget of a cold mass using reanalysis poses significant challenges.”</p>
<p>While recent research provides valuable insights, experts like <a href="https://profiles.ucl.ac.uk/38605-david-thornalley">David Thornalley</a> from University College London caution that definitive conclusions about the causes of cold blobs remain elusive.</p>
<p>Limited data prevents us from entirely ruling out alternative explanations. For instance, <a href="https://www.sams.ac.uk/people/researchers/fraser-dr-neil/">Neil Fraser</a> from the Scottish Marine Science Society notes that a tributary of the AMOC, known as the Norwegian Current, may be strengthening and transporting additional heat away from the cold mass regions.</p>
<p>In conclusion, while the existence of the cold mass aligns with AMOC weakening, conclusive evidence remains to be established.</p>
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Source: www.newscientist.com

How Reducing Air Pollution May Impact Key AMOC Currents

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Smog particles reflecting sunlight

Smog Contains Particles That Reflect Sunlight and Cool Earth’s Surface

Credit: Dennis McDonald/Alamy

Addressing air pollution in Europe and North America could inadvertently weaken the Atlantic Meridional Circulation (AMOC), a crucial ocean current influencing Europe’s climate.

Air pollution, including smog and soot, claims approximately 7 million lives annually and contributes to widespread health issues. Interestingly, aerosols, which are tiny particulate pollutants like sulfur dioxide, can reflect sunlight, making clouds brighter and reducing surface heat absorption.

Recent research indicates that reducing air pollution from maritime sources and other sectors could accelerate global temperature increases. “If we cut back on aerosols, we will start to see the extent of warming,” says Michael Diamond from Florida State University.

Historically, scientists’ insights into aerosols’ climatic impact have relied on global simulations akin to those used for examining the greenhouse effect. These models suggest that “higher aerosol levels cool the North Atlantic surface and strengthen the AMOC,” according to Robert Allen from the University of California, Riverside. Conversely, if global aerosol emissions are reduced, the Earth’s surface may warm, weakening the AMOC.

Nonetheless, these simulations often overlook the regional characteristics of air pollution. Unlike greenhouse gases, which linger in the atmosphere for years, most aerosols dissipate within a week, meaning their climatic effects typically manifest close to their source, revealing the complex consequences of pollution reductions.

To gain deeper insights into the impacts of clean air initiatives, Allen and his team employed eight distinct climate models to assess how changes in regional aerosol emissions impact both local and global climates. The models evaluated AMOC strength under high-emission scenarios established by the Intergovernmental Panel on Climate Change and reformulated these scenarios with enhanced air quality regulations.

The findings indicate that if greenhouse gas emissions continue to rise but aerosol pollutants decrease, the AMOC could weaken by a third by mid-century compared to scenarios where aerosol levels remain elevated.

While Allen’s research does not delve into the regional weather implications of AMOC weakening, previous studies suggest that such a decline could lead to adverse outcomes, including increased droughts across Europe, exacerbated sea level rise in northeastern North America, and disruption of global monsoons and rising temperatures in Northern Europe.

Allen’s analysis revealed that the most significant impact on AMOC would stem from reduced aerosol levels in Europe and North America. However, he noted that air quality improvement initiatives in East Asia are also proving impactful. Cleaner air in East Asia is affecting global temperatures—despite their short lifespan, aerosols can travel long distances and mask warming effects wherever they reach, potentially leading to further weakening of the AMOC.

“To improve air quality, we must acknowledge that there will be associated climate changes,” Allen states. “To achieve clean air while minimizing our climate impact, we must simultaneously reduce other greenhouse gases like CO2 and methane.”

Diamond echoes this sentiment, stating, “When considering clean air policies, it’s vital to concurrently address decarbonization strategies.”

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Source: www.newscientist.com

How a Massive Bering Strait Dam Could Prevent AMOC Collapse

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The Bering Strait

The Bering Strait separates Alaska and Russia

Ocean Color/OB.DAAC/OBPG/NASA

An ambitious engineering project looms on the horizon: constructing a dam between Alaska and eastern Russia. This innovative proposal aims to combat the dire consequences of a weakening ocean current, and is under serious consideration at a prominent conference this week.

The seeds of this groundbreaking idea were sown by Jere Soon and his collaborator Henk Dijkstra, a researcher focused on the Atlantic Meridional Overturning Circulation (AMOC) at Utrecht University, Netherlands. This current system, including the Gulf Stream, is crucial for keeping northern Europe warmer than its geographical latitude would suggest.

Current data indicates that the AMOC is weakening. The potential effects of its collapse are uncertain, but many models hint at a possible significant drop in temperatures across Northern Europe.

The concept was inspired by the Pliocene era, when sea levels were considerably lower and a land bridge existed where the Bering Strait now lies. During this time, simulations revealed a stronger AMOC due to the presence of this land bridge. “I thought: can we replicate this?” says Soon.

To explore the implications of such dam construction, Soon and Dijkstra simulated various AMOC scenarios, adjusting the construction date and freshwater levels.

Freshwater plays a crucial role in this dynamic, currently flowing from the Pacific Ocean into the North Atlantic through the Bering Strait, which in turn disrupts the AMOC. Constructing a dam could either halt or considerably slow this freshwater flow.

In a recent study, Soons and Dijkstra obtained mixed results: in certain scenarios, dams seemed to enhance the AMOC, while in others, they produced the opposite effect. It’s important to note that these findings were derived from relatively basic, low-resolution models.

On May 5, Dr. Soons presented significant research results at the European Geosciences Union General Assembly in Vienna, Austria. Simulations were re-evaluated using a supercomputer that employed advanced climate models. The results indicate that closing the strait could reinforce the AMOC, particularly if dams are constructed by 2050. “I was surprised at how robust the recovery was,” Soon remarked.

The Bering Strait, at its deepest point, measures only 59 meters and features two small islands in the middle, suggesting the viability of constructing a barrier. Ed McCann, former president of the Japan Society of Civil Engineers and current head of expedition engineering, suggests that rather than concrete, using flotation machinery to build barriers with rock and dredged sand would be most efficient. “This type of construction is straightforward, albeit large-scale and costly,” he commented via email.

Jonathan Rosser, a researcher at the London School of Economics, finds the study intriguing. However, he emphasizes that due to the AMOC’s complexities, we cannot fully predict the outcomes of such interventions. “These drastic measures come with significant uncertainty.”

Suhn concurs, cautioning that while dam construction may benefit Northern Europe, it could lead to adverse effects elsewhere, such as altered rainfall patterns. “Are we ready to take this seriously? I don’t think we’re there yet,” he concluded.

This isn’t the first consideration of constructing gigantic ocean dams to address climate change. In 2020, Sjoerd Groeskamp from the Royal Netherlands Marine Institute proposed the “Northern European Enclosure Dam,” designed to create barriers around the sea between the UK and mainland Europe, protecting low-lying areas from rising seas.

Such dams would undoubtedly impact not only the climate but also marine mammal migration, tidal patterns, and transport access to isolated regions. Mr. Soons noted that he has explored ideas like constructing partial barriers or lowering them to a depth of approximately 10 meters. These concepts are “interesting,” he said, though he has yet to thoroughly analyze their feasibility.

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Source: www.newscientist.com

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

noaa

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.

jens carsten roseman

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