The Atlantic meridional overturning circulation (AMOC) is the main ocean current system in the Atlantic Ocean. It is part of Earth's ocean circulation system and plays an important role in the climate system. The AMOC includes surface and deep ocean currents in the Atlantic that are driven by changes in weather, temperature, and salinity. These currents make up half of the global thermohaline circulation, which includes the movement of major ocean currents. The other half of this circulation occurs in the Southern Ocean.
The AMOC has two main parts: a northward flow of warm, salty water in the upper layers of the Atlantic, and a southward flow of cold, less salty water in the deep ocean. Warm water from the southern regions becomes saltier because of higher evaporation rates in tropical areas. This salty, warm water forms the upper layer of the ocean. When this layer cools, the salt increases the water's density, causing it to sink into the deep ocean. This process is a key part of how the AMOC works. The two parts of the AMOC are connected by overturning regions in the Nordic Seas and the Southern Ocean. These areas are important for exchanging heat, oxygen, carbon, and other nutrients. They support ocean ecosystems and help the ocean store carbon. Changes in the strength of the AMOC can affect many parts of the climate system.
Climate change might weaken the AMOC by increasing ocean heat and adding more freshwater from melting ice sheets. Studies suggest that by 2015, the AMOC was weaker than it was before the Industrial Revolution. Scientists are still discussing whether this weakening is mainly due to climate change or natural changes that occur over long periods. Climate models predict the AMOC will weaken further during the 21st century. This weakening could lower average air temperatures in Scandinavia, Great Britain, and Ireland because these regions are warmed by the North Atlantic Current. It could also increase sea level rise near North America and reduce the growth of ocean plants in the North Atlantic.
If the AMOC weakens severely, the circulation could collapse. A collapse would be hard to reverse and could act as a tipping point in the climate system. This would greatly lower average temperatures and rainfall in Europe. It might also increase the frequency of extreme weather events and cause other serious effects.
Overall structure
The Atlantic meridional overturning circulation (AMOC) is the main current system in the Atlantic Ocean. It is part of the global thermohaline circulation, a system that connects all the world’s oceans through a continuous flow of water, like a conveyor belt. Normally, warm and less salty water stays near the ocean’s surface, while deeper water is colder, denser, and saltier. This separation of water layers is called ocean layering. Over time, deep water gains heat or loses salt through mixing with the surface layer, becoming less dense and rising. Differences in temperature and salt levels between ocean layers and regions drive the thermohaline circulation. The Pacific Ocean has less salt than other oceans because it receives large amounts of fresh rain. Its surface water is not salty enough to sink deep, so deep water in the Pacific must come from other areas.
In the North Atlantic, ocean water is saltier than in the Pacific. This is partly because evaporation on the surface removes water, leaving salt behind. It is also because sea ice near the Arctic releases salt as it freezes. Additionally, moisture evaporated from the Atlantic is carried by wind across Central America to the eastern North Pacific, where it falls as rain. Major mountain ranges, such as the Tibetan Plateau, Rocky Mountains, and Andes, block the return of this moisture to the Atlantic.
Because of these processes, Atlantic surface water becomes salty and dense, eventually sinking to form the North Atlantic Deep Water (NADW). NADW forms mainly in the Nordic Seas, where different water masses, like Denmark Strait Overflow Water and Iceland-Scotland Overflow Water, mix. Water from the Labrador Sea may also play a role, but recent evidence suggests most of it recirculates within the North Atlantic and does not directly connect to the AMOC.
The NADW is not the deepest water layer in the Atlantic. The densest and deepest layer is Antarctic Bottom Water (AABW), found in basins deeper than 4,000 meters. As AABW rises, it merges with NADW, strengthening it. The formation of NADW starts the lower part of the circulation. The sinking of NADW is balanced by rising water elsewhere. In the western Atlantic, wind-driven ocean mixing causes strong upwelling near the Canary Current and Benguela Current, located on Africa’s northwest and southwest coasts. Upwelling is stronger near the Canary Current than the Benguela Current, though this pattern changed after the Central American Seaway closed during the late Pliocene. In the eastern Atlantic, upwelling happens only during certain months because deep water layers depend more on surface temperatures than wind. A multi-year upwelling cycle also occurs in sync with the El Niño/La Niña weather pattern.
As NADW moves southward, most of it rises near the Southern Ocean, connecting to the Southern Ocean overturning circulation. After rising, some water near Antarctica is cooled by sea ice and sinks again, rejoining the AABW. Other water flows into the Pacific and Indian Oceans. Water that rises at lower latitudes moves northward due to wind-driven mixing and joins the upper part of the circulation. Warm water in the upper part returns to the North Atlantic, mainly near Africa and through the Indonesian archipelago. Once this water reaches the North Atlantic, it cools and becomes denser, sinking again to feed the NADW.
Role in the climate system
Equatorial areas are the hottest parts of the Earth. Because of heat movement, this heat travels toward the poles. Most of this heat is carried by air movement, but warm ocean currents also help move it. Heat from the equator moves either north or south. In the Atlantic Ocean, heat flows northward. Much of the heat movement in the Atlantic happens through the Gulf Stream, a surface current that carries warm water north from the Caribbean. While the Gulf Stream is mainly driven by wind, its northern part, the North Atlantic Current, gains heat from salt and temperature changes in the AMOC. This means the AMOC moves up to 25% of the Earth’s heat toward the northern hemisphere and helps shape the climate in northwest Europe.
Air patterns also help move heat, so the idea that northern Europe would be as cold as northern North America without ocean currents is not widely accepted. Some studies suggest that if the AMOC collapsed, it might cause cooling similar to an ice age, but these results are uncertain. Scientists agree that the AMOC keeps northern and western Europe warmer than it would be otherwise. For example, the temperature difference is about 4°C (7.2°F) to 10°C (18°F), depending on the area. Studies of the Florida Current show that the Gulf Stream was weaker between 1200 and 1850 due to higher salt levels in the ocean, which may have contributed to a period called the Little Ice Age.
The AMOC helps the Atlantic Ocean absorb more carbon in two ways. First, rising water from the deep ocean brings nutrients to the surface, which supports the growth of phytoplankton and increases the amount of photosynthesis in the ocean. Second, the upwelled water is old and has not absorbed recent carbon dioxide from the atmosphere. This water absorbs more carbon than surface water and keeps it from returning to the atmosphere when it sinks. While the Southern Ocean is the strongest carbon sink, the North Atlantic is the largest single carbon sink in the northern hemisphere.
The AMOC depends on interactions between ocean water layers of different temperatures and salt levels. It is not static but changes over time in response to outside factors. Many of these changes happened during the Late Pleistocene (126,000 to 11,700 years ago), the last major ice age before the current warm period. This time includes the Last Glacial Period, known as the "last ice age." During this time, there were 25 sudden temperature changes between the hemispheres, called Dansgaard–Oeschger events (D-O events). These events were discovered by studying ice cores from Greenland in the 1980s.
D-O events are known for rapid warming in Greenland, with temperatures rising 8°C to 15°C (15°F to 27°F) over decades. Similar warming happened across the North Atlantic, but the Southern Ocean cooled at the same time. This pattern matches the AMOC moving more heat between hemispheres. Warming in the northern hemisphere likely caused ice sheets to melt, and many D-O events ended when massive icebergs broke off from the Laurentide ice sheet. As the icebergs melted, the ocean became less salty, slowing the AMOC and ending the warming.
Scientists have not agreed on why the AMOC changed so much during the ice age. Some ideas include salt level changes in the North Atlantic or wind patterns affected by ice sheets. Research from the 2010s suggests the AMOC was most sensitive to change during times with large ice sheets and low carbon dioxide levels, making the Last Glacial Period a key time for these events. Some studies suggest warming in the southern hemisphere started the pattern, as warmer water moved north through ocean currents. However, evidence is not strong enough to say whether the AMOC changed first or responded to other factors, such as changes in sea ice.
D-O events are numbered from oldest to youngest. The last major event, D-O event 1, happened about 14,690 years ago and marked the end of a cold period called the Oldest Dryas and the start of a warmer period called the Bølling–Allerød Interstadial. This period lasted until about 12,890 years ago and was named after sites in Denmark with fossils from warm-weather plants. The warming in the northern hemisphere was balanced by cooling in the southern hemisphere, with little overall change in global temperatures. This matches the AMOC’s movement of heat. The warm period also caused a rise in sea levels due to melting ice sheets, called Meltwater pulse 1A.
The Bølling and Allerød stages were separated by a short time when the northern hemisphere cooled and the southern hemisphere warmed, called the Older Dryas. This period was named after a plant, Dryas octopetala, that grew in colder conditions. The warm period ended with the Younger Dryas (12,800–11,700 years ago), when northern hemisphere temperatures dropped to near-ice age levels. This happened because the AMOC slowed, likely due to fresh water from melting ice sheets in North America. Unlike true ice sheet collapses, this event involved a large flow of meltwater from the Mackenzie River in Canada. Changes in rainfall patterns, such as increased rain in North America and droughts in South America and Europe, also occurred. Global temperatures remained stable during the Younger Dryas, and warming resumed after it ended.
Stability and vulnerability
The AMOC has not always existed. For much of Earth's history, ocean currents in the northern hemisphere moved mainly in the North Pacific. Evidence from ancient climates shows that the movement of ocean currents shifted from the Pacific to the Atlantic about 34 million years ago, during a time called the Eocene-Oligocene transition. This shift happened when a passage between the Arctic and Atlantic Ocean closed. This change greatly altered how ocean currents move based on temperature and salt differences. Some scientists think that future climate changes might one day reverse this shift and bring ocean currents back to the Pacific if the AMOC stops working. Climate change affects the AMOC by warming surface water due to Earth's energy imbalance and by reducing the saltiness of surface water. This happens because melting ice, especially from Greenland, adds large amounts of fresh water to the ocean, and because more rain falls over the North Atlantic. These changes increase the difference between surface and deep ocean layers, making it harder for the upwelling and downwelling that drive the AMOC to happen.
In the 1960s, a scientist named Henry Stommel studied the AMOC and created a model called the Stommel Box model. This model introduced the idea of Stommel Bifurcation, which suggests the AMOC can exist in two states: a strong state, like the one seen in recorded history, or a weak state where it nearly stops working. The AMOC could return to its strong state only if warming and fresh water inputs that caused the weakening are reduced. Warming and fresh water could directly cause the AMOC to weaken or collapse, or they could push the AMOC past a tipping point where small changes in the system lead to a sudden collapse. Scientists have long debated whether the AMOC is a system that can be either "on" or "off" and whether it might collapse suddenly.
Some models developed after Stommel's work suggest the AMOC might exist in one or more stable states between full strength and full collapse. These states are more common in Earth Models of Intermediate Complexity (EMICs), which focus on parts of the climate system like the AMOC and ignore other factors. More detailed general circulation models (GCMs), which are considered the best for simulating the whole climate, often show the AMOC has only one stable state and is unlikely to collapse. Scientists have raised concerns that GCMs may not accurately reflect real-world conditions because they often move large amounts of fresh water toward the North Pole, where it does not affect the AMOC.
In 2024, three researchers used a model called the Community Earth System Model (CESM) to simulate the AMOC. Their simulation showed a classic collapse of the AMOC, similar to what happens in simpler models. Unlike some other studies, they gradually increased the amount of fresh water added to the model over 1,700 years. The simulation reached fresh water levels equivalent to a sea level rise of 6 centimeters (2.4 inches) per year, which is much higher than the 2.9 millimeters (0.11 inches) per year observed between 1993 and 2017. The researchers said these extreme conditions were used to test the model and should not be seen as predictions. Instead, the results show how ocean currents might change before a collapse. Other scientists agreed the study would help improve future research, especially once more accurate data is available.
Some research suggests that models using EMICs may overestimate the likelihood of AMOC collapse because they assume a constant flow of fresh water. In one study, changing the flow of fresh water from constant to variable delayed the collapse of the AMOC in a model by over 1,000 years. This result matched observations from a time about 13,500 to 14,700 years ago, when large amounts of fresh water entered the ocean. A 2022 study found that the AMOC had a limited response to massive fresh water inputs during the final stage of the last ice age, about 11,700 to 6,000 years ago, when sea levels rose by about 50 meters (160 feet). This suggests that many models may overestimate how much fresh water affects the AMOC. If the AMOC depends more on wind strength, which changes little with warming, it might be more resistant to collapse. Some scientists think the Southern Ocean overturning circulation (SOOC) might be more likely to collapse than the AMOC.
High-quality models of Earth's systems suggest that a collapse of the AMOC is unlikely unless warming reaches very high levels (4°C or higher) and continues for many years after 2100. Some studies of ancient climates support this idea. However, some scientists believe that simpler models, which predict an earlier collapse, might be more accurate. One such model suggested the AMOC could collapse around 2065, but many scientists are unsure about this prediction. Some research also suggests the SOOC might be more vulnerable to collapse than the AMOC. In October 2024, 44 climate scientists published a letter stating that recent studies suggest the risk of AMOC collapse has been underestimated and that it could happen in the next few decades, causing serious problems for Nordic countries. They urged Nordic nations to follow the Paris Agreement to prevent this. A 2026 study using high-resolution models found that the AMOC might collapse more easily than previously thought, as it is more sensitive to fresh water inputs than earlier models suggested.
Trends
Until 2024, scientists noticed a difference between observations showing a slower ocean current called the AMOC and models predicting a stable current. In November 2024, a study published in Nature Geoscience used advanced models that simulate ocean and sea ice movements. This helped match observations and models more closely. The study found the AMOC has slowed by 0.46 sverdrups each decade since 1950.
Direct measurements of the AMOC’s strength began in 2004 using the RAPID system, which uses underwater sensors at 26°N in the Atlantic. Observations need long-term data to be useful. Some scientists used smaller-scale data, like submarine research in 2005 that found weaker water movement in the Greenland Sea, a part of the AMOC. In 2000, other studies looked at the North Atlantic Gyre (NAG), which showed a 30% drop in strength between 1992 and 2004. However, later RAPID data showed this was a statistical error, and the NAG recovered by 2008. Now, it is known the NAG operates separately from the rest of the AMOC and could weaken on its own.
By 2014, RAPID data up to 2012 showed a decline in AMOC strength 10 times larger than predicted by models. Scientists debated whether this was due to climate change or natural changes. Data up to 2017 showed a large drop in 2008–2009, but the AMOC remained weaker than it was in 2004–2008.
The AMOC is also measured by tracking heat transport. In 2017 and 2019, data from NASA satellites and Argo floats suggested 15–20% less heat movement than RAPID measurements, showing a stable flow with limited changes.
Measurements of the Florida Current, corrected for Earth’s magnetic field changes, have shown stable strength over the past 40 years.
Climate reconstructions use past data to study the AMOC, though they are less reliable than direct measurements. In 2021, RAPID data combined with older reconstructions showed no overall AMOC decline in the past 30 years. A 2020 study found no major changes in AMOC circulation compared to the 1990s, though changes occurred in the North Atlantic. A 2022 review noted global warming may weaken the AMOC long-term, but changes since 1980 are hard to detect due to both weakening and strengthening periods.
Some reconstructions compared the AMOC’s current state to earlier times. A 2010 study found the AMOC has weakened since the 1930s, with a major shift around 1970. A 2015 study linked temperature patterns to a 15–20% AMOC weakening over 200 years, with the strongest slowdown in the 20th century. A 2018 study suggested a 15% weakening since the mid-20th century. A 2021 reconstruction using ocean temperature and salinity data showed significant changes in eight AMOC indicators, suggesting instability. This study excluded data from 1900–1980 to ensure consistency. However, 2022 research using data from 1900–2019 found no AMOC changes between 1900–1980, with a small decline starting in 1980.
Sediment studies showed the AMOC weakened by 20% since the mid-20th century. A 2018 study found the AMOC has been unusually weak in the last 150 years compared to the past 1,500 years. A 2017 review found evidence of past AMOC changes during abrupt climate events. A 2022 study linked Atlantic long-term changes to reduced stability, possibly connected to the AMOC.
A 2021 study in Nature Geoscience claimed the AMOC weakened by 15% due to human actions, predicting further weakening in 20–30 years. This was challenged in 2022 by scientists who said long-term AMOC trends remain uncertain.
Some researchers link recent climate changes to AMOC weakening. For example, a North Atlantic area near Greenland cooled by 0.39°C (0.70°F) between 1900–2020, unlike other warming ocean areas. This cooling is seasonal, most noticeable in February, but still warmer than pre-industrial levels in summer. Between 2014–2016, this area stayed cool for 19 months, called the "cold blob."
The cold blob occurs when fresh, cool water avoids sinking, slowing the AMOC. Later research found atmospheric changes, like increased low cloud cover and stronger North Atlantic oscillation, also contributed to this pattern.
Projections
Historically, CMIP models, the most trusted method in climate science, show the AMOC is very stable. Although it may weaken, it will always recover rather than permanently collapse. For example, in a 2014 controlled experiment where CO₂ levels doubled from 1990 values and stayed the same, the AMOC declined by about 25% but did not collapse. It recovered slightly, by about 6%, over the next 1,000 years. In 2020, research estimated that if warming stops at 1.5°C (2.7°F), 2°C (3.6°F), or 3°C (5.4°F) by 2100, the AMOC would weaken for 5–10 years after warming stops but would not collapse. It would partially recover after about 150 years. Many scientists say collapse is avoided only because models have long-term errors.
While models have improved over time, the sixth and current generation of CMIP6 models still have some inaccuracies. On average, these models show greater AMOC weakening in response to greenhouse warming than earlier models. When four CMIP6 models simulated the AMOC under the SSP3-7 scenario, where CO₂ levels more than double from 2015 values (from about 400 parts per million to over 850 ppm) by 2100, they found the AMOC declined by over 50% by 2100. These models still struggle to simulate North Atlantic Deep Water (NADW) without errors in its depth or area, which reduces confidence in their predictions.
To improve accuracy, scientists tested bias correction in models. In one experiment, applying bias correction to a model caused the AMOC to collapse after 300 years. In 2016, a study combined results from eight CMIP5 models with improved Greenland ice melt estimates. It found that under the intermediate RCP 4.5 scenario, the AMOC would weaken by about 18% by 2090–2100, and by 37% under the high RCP 8.5 scenario. When these scenarios were extended past 2100, the AMOC stabilized under RCP 4.5 but continued to decline under RCP 8.5, leading to a 74% decline by 2290–2300 and a 44% chance of complete collapse. In 2020, another study used a model with advanced ocean physics. It found similar results under RCP 4.5 but showed the AMOC declined by two-thirds after 2100 under RCP 8.5, without collapsing.
In 2023, a statistical analysis of multiple models suggested the AMOC might collapse around 2065, with a 95% chance of collapse between 2037 and 2109. This study was widely discussed because intermediate-complexity models are less reliable and may confuse a major slowdown with complete collapse. The study used temperature data from the Northern Subpolar Gyre, which some scientists say does not represent the whole AMOC. Experts called the research "worrisome" but noted it could be useful once better data is available. They agreed the study’s data was "insufficient."
A 2025 analysis extended CMIP6 simulations beyond 2100 and tracked the deep northern overturning cell (linked to NADW). Under the high-emissions SSP5-8.5 scenario, models showed the overturning cell weakened from about 14–26 Sv to 1–6 Sv by 2100. This was accompanied by a sudden shift in the depth of maximum overturning. The models showed deep winter convection in subpolar regions stopped about 30 years before the overturning cell collapsed, which aligns with feedbacks like Welander and Stommel. The models also showed a shallow, wind-driven overturning cell remained active after the collapse.
Large review papers and reports can evaluate model results, direct observations, and historical data to make expert judgments. The IPCC Third Assessment Report (2001) projected high confidence that the AMOC would weaken but not stop, with warming effects outweighing cooling. The Fifth Assessment Report (2014) said a rapid AMOC transition was "very unlikely." The Sixth Assessment Report (2021) stated the AMOC is "very likely" to weaken in the 21st century and that changes would be reversible if warming stops. It had "medium confidence" in avoiding collapse by 2100, a lower confidence than the Fifth Assessment Report. This change was likely due to studies showing model biases and simpler models suggesting the AMOC may be more vulnerable to sudden changes.
The IPCC Sixth Assessment Report summarized that the AMOC is "very likely" to weaken by the end of the century but "not expected" to collapse before 2100. If a collapse occurred, it would likely cause sudden changes in weather patterns and water cycles, such as shifting tropical rain belts and affecting ecosystems and human activities.
In 2022, a review of climate tipping points identified 16 possible tipping points, including AMOC collapse. It estimated collapse would most likely occur at 4°C (7.2°F) of warming but could happen between 1.4°C (2.5°F) and 8°C (14°F). Once triggered, collapse would take 15–300 years, most likely around 50 years. The Northern Subpolar Gyre was also identified as a separate tipping point, likely to tip at 1.8°C (3.2°F) and collapse within 5–50 years. This collapse could lower global temperatures by 0.5°C (0.9°F) and reduce European temperatures by 3°C (5.4°F), with major effects on regional rainfall.
The "
Effects of AMOC slowdown
As of 2024, scientists have not reached an agreement about whether the Atlantic Meridional Overturning Circulation (AMOC) has been slowing down consistently. However, most experts believe that if climate change continues, the AMOC will likely slow down in the future. According to the Intergovernmental Panel on Climate Change (IPCC), a weaker AMOC could lead to less rain in the middle parts of the Earth, more intense rain in tropical and European regions, and stronger storms that move along the North Atlantic. A 2020 study found that a weaker AMOC might slow the loss of Arctic sea ice and cause weather patterns similar to those during the Younger Dryas period, such as the Intertropical Convergence Zone shifting southward. These changes would be much more severe under high-emissions scenarios.
A weaker AMOC could also speed up rising sea levels along the U.S. East Coast. At least one event linked to a temporary slowdown of the AMOC has already been recorded. This would happen because warmer coastal waters expand, trapping more heat near the coast instead of moving it toward Europe. This is why sea level rise along the U.S. East Coast is expected to be three to four times higher than the global average.
Some scientists think a partial slowdown of the AMOC might cause Europe to cool slightly by about 1 degree Celsius (1.8 degrees Fahrenheit). Other regions would be affected differently. A 2022 study found that Siberian winter weather extremes were milder when the AMOC was weaker. One analysis suggested that a slower AMOC might lower the economic costs of carbon emissions by about 1.4%, because Europe contributes a larger share of the world’s economy than the regions harmed by the slowdown. However, this study’s methods may have underestimated overall climate impacts. Some research argues that a slower AMOC could reduce the ocean’s ability to absorb heat, leading to faster global warming, though this view is not widely accepted.
A 2021 study found that other major climate tipping points, such as the melting of the Greenland and West Antarctic ice sheets and the decline of the Amazon rainforest, are connected to the AMOC. While changes to the AMOC alone may not directly trigger these tipping points, a slower AMOC could link them together. This connection might lower the global warming threshold at which these tipping points occur, compared to thresholds studied individually. This could lead to a chain reaction of tipping events over several centuries.
Effects of an AMOC shutdown
A complete stop of the AMOC would be very hard to fix, and it might take thousands of years to recover. If the AMOC stops, Europe, especially Britain, Ireland, France, and the Nordic countries, could experience large temperature drops. In 2002, research compared an AMOC shutdown to Dansgaard–Oeschger events, which were sudden temperature changes during the Last Glacial Period. That study said Europe could cool by up to 8 °C (14 °F). In 2022, a major review of tipping points said an AMOC collapse would lower global temperatures by about 0.5 °C (0.90 °F), while Europe’s temperatures could fall by 4 °C (7.2 °F) to 10 °C (18 °F).
In 2020, a study looked at how an AMOC collapse would affect farming and food production in Great Britain. It found that, after accounting for warming effects, temperatures in Britain could drop by an average of 3.4 °C (6.1 °F). Rainfall during the growing season would also decrease by about 123 mm (4.8 inches), reducing arable land from 32% to 7%. This could lower the value of British farming by about £346 million per year, which is over 10% of its 2020 value.
In 2024, a study modeled the effects of an AMOC collapse on a pre-industrial world. It predicted a severe temperature drop in northwest Europe, with sea surface temperatures falling by 10 °C (18 °F) and land temperatures in northern and western Europe dropping by 10 °C (18 °F) to 30 °C (54 °F) within a century. This could bring sea ice into the territorial waters of the British Isles and Denmark during winter, while Antarctic sea ice might decrease. These findings do not include warming from climate change, and the study’s methods are debated.
In 2015, a study led by James Hansen found that a slowdown or stop of the AMOC could make severe weather worse by increasing baroclinicity and speeding up northeasterly winds by 10–20% in the mid-latitude troposphere. This might lead to more frequent winter and near-winter cyclonic "superstorms" with strong winds and heavy snowfall. This paper is also debated.
Several studies have examined how an AMOC collapse might affect the El Niño–Southern Oscillation (ENSO). Results vary, from no major impact to stronger ENSO activity, more frequent La Niña conditions, and changes in rainfall and drought patterns in Australia and the southwestern U.S.
In 2021, a study used a simplified model to evaluate how an AMOC collapse might affect the Amazon rainforest. It found that the collapse could increase rainfall in the southern Amazon due to a shift in the Intertropical Convergence Zone, which might help prevent the rainforest from shrinking into a savanna. A 2024 study suggested that the Amazon’s seasonal cycle could reverse, with dry seasons becoming wet and wet seasons becoming dry.
In 2005, a paper said a severe AMOC disruption would reduce North Atlantic plankton populations to less than half their normal levels because of increased ocean layer separation and reduced nutrient mixing. In 2015, a study simulated global ocean changes under AMOC slowdown or collapse scenarios. It found that these events would greatly lower dissolved oxygen in the North Atlantic, though oxygen levels might slightly rise globally due to increases in other ocean regions.