The Impacts of an AMOC collapse on Europe


The impacts of an AMOC collapse on Europe



Introduction

As the Earth has warmed, one section of the Atlantic Ocean has been cooling. This has been attributed to an ocean current, known as the Atlantic Meridional Overturning Circulation (AMOC) weakening. This ocean current regulates the climate worldwide by transporting waters at different temperatures, but this is expected to continue to weaken with climate change, bringing worrying consequences on the climate. However, a more extreme, but still a very plausible scenario of the current collapsing may occur as early as mid-century, where the climate may rapidly change within a few decades. In this summary, I'll focus on Europe.
Source: High-resolution ‘fingerprint’ images reveal a weakening Atlantic Ocean circulation (AMOC)
The AMOC brings warmer water from the Gulf of Mexico to Europe, contributing to keeping its climate mild in comparison to areas such as Canada. Under a collapse, a lot of the warmer water is shut off, shown by the figure above. It would be logical to assume a clear cooling of the climate, and a drying of all seasons as a result of colder waters providing less moisture, but many atmospheric feedbacks would interact to produce a much more complex outcome. This includes changes in sea ice (1, 13), and in global wind patterns (4, 5, 6, 7, 15).


Climate model simulations

Temperature

Source: amocscenarios.org, (1), pre-industrial scenario
Source: amocsenarios.org, (1), moderate emission scenario
Source: (3), moderate/high emission scenario
Source: amocscenarios.org, (1), high emission scenario
Without climate change, the whole of Europe faces a notable cooling of the climate, where north-western Europe re-enters ice age conditions as the colder sea temperatures, which then correspond to colder air temperatures allows for sea ice expansion, which then leads to further drops of temperature, and so on. In winter, this cooling of the climate is exceptionally severe. Simulations that include global warming are much more realistic. In these more realistic simulations, it's clear that the cooling is heavily muted. In a moderate emission scenario, the majority of Europe cools, except for the south of Europe. In a moderate to high emission scenario, this cooling is limited to the British Isles, Scandinavia, and Iceland. In a high emission scenario, only a reduced level of warming is observed. It's also notable that the heaviest cooling impacts are in north Scotland, western Norway and Iceland. In addition, the changes in temperature are seasonal. While only the far south of Europe avoids a net cooling in winter, only the northwest of Europe sees a net cooling in summer in a moderate emission scenario. However, in the high emission scenario, there’s no net cooling in Europe. The reason for the extent of cooling to be so heavily offset is the reduction of the expansion of sea ice (1, 13), and the atmosphere reorganizing (5, 6).

Precipitation (14)

Pre-industrial scenario - top row
Moderate emission scenario - 2nd row
High emission scenario - bottom row
Annual precipitation anomalies - left column
Dry season intensity - right column
Following an AMOC collapse, here's a drier summer across Europe, particularly in the south, and these impacts are exacerbated by global warming. Given that a combination of the yearly-averaged precipitation and dry season intensities can be used to estimate the winter changes, global warming reduces the drying of the winter climate, where the northern half of Europe may experience wetter winters, particularly in a high emission scenario as a result of a strengthened jet stream and storm track. In addition, a combination of an AMOC collapse scenario can lead to a lengthening of the dry season.

Jet stream (1)

Pre-industrial scenario
Moderate emission scenario
High emission scenario

After the AMOC collapses, there's an increase in the gradient of sea temperatures, leading to the jet stream accelerating (17) and shifting northeast into Europe. This acceleration of the jet stream is especially stark when combined with global warming. As a result, the storm track is intensified, leading to higher wind speeds (18), and cold spells decrease in both frequency and length (19)

Sea level (2)

As the AMOC is an ocean current, a shutdown would lead to changes in sea level, such as a rise of several tens of centimetres across Europe, including the Mediterranean Sea, the North Atlantic, and nearly a metre of sea level rise in the Artic Ocean. In addition, ice melt from global warming would further contribute to this sea level rise.



Observed climate change

Winter

Source: (7)
Sea level pressure (top figure)
Sea surface temperature (bottom figure)

Surprisingly, following increased freshwater in the North Atlantic (therefore weakening the AMOC, and leading to colder sea surface temperatures), there is no cooling of European winters (15). Instead, it results in a strengthened, jet stream that compensates for the expected cooling of winters (4, 15, 7). In addition, the strengthened sea surface temperature contrast drives the North Atlantic Current north (20), which then transports warmer sea surface temperatures just south of the anomalous cold temperatures, which further reduces the cooling of European winters. This contrasts with climate model simulations, which suggest a cooling of the European climate in response to an AMOC weakening (13, 18), carrying implications for simulations of an AMOC collapse, where climate models may be overestimating the cooling. Also, this leads to stormier winters

Summer

Source: (7)

Increasing freshwater in the North Atlantic, resulting in colder sea surface temperatures results in warmer European summers, aside from Scandinavia (7, 12). In addition, the Younger Dryas saw warmer European summers from an AMOC collapse (11), despite lacking the rapid global warming of recent decades, and having far more ice in the Northern Hemisphere to amplify the climate cooling. This also contrasts with climate model simulations of an AMOC weakening/collapse, where summers still cool (1, 2, 18, 19), suggesting that they have a bias to overestimate the cooling following an AMOC collapse. This warming of summers is due to the North Atlantic Current and the jet stream moving north (20).

Sea ice

Both (1, 13) show that the extent of the climate cooling in Europe following an AMOC collapse is heavily reliant on the expansion of sea ice. However, the climate models used to simulate the impacts of an AMOC collapse have been underestimating the retreat of sea ice during global warming (8, 9), which may be a leading cause towards the bias of climate models overestimating the cooling of the climate, meaning that even with a moderate-emission scenario, the impacts may be closer to that of high-emission scenarios. 



Conclusions

In the context of anthropogenic global warming, an AMOC collapse can have concerning impacts on the European climate that can set in within a few decades. In winter, this may result in the expected warming in northwest Europe being offset, and possibly temporarily reversed. Across Europe, impacts may include a northward shift of, and a strengthening of the jet stream, resulting in a reduction in the frequency of cold spells, and a stronger storm track. In contrast, an AMOC collapse would lead to drier summers, raising the risk of droughts during the growing season, and contribute to higher temperatures and heatwaves, excluding in Scandinavia. In addition, an AMOC collapse leads to a greater magnitude of sea level rise.



References

(1) European Temperature Extremes Under Different AMOC Scenarios in the Community Earth System Model
    https://doi.org/10.1029/2025GL114611
(2) Physics-based early warning signal shows that AMOC is on tipping course
    https://doi.org/10.1126/sciadv.adk1189
(3) Overlooked possibility of a collapsed Atlantic Meridional Overturning Circulation in warming climate
    https://doi.org/10.1126/sciadv.1601666
(4) Ocean versus atmosphere control on western European wintertime temperature variability
    https://doi.org/10.1007/s00382-015-2558-5
(5) Atmospheric Response to a Collapse of the North Atlantic Circulation
    https://doi.org/10.1175/JCLI-D-22-0841.1
(6) Future climate change shaped by inter-model differences in Atlantic meridional overturning circulation response
    https://doi.org/10.1038/s41467-021-24015-w
(7) European summer weather linked to North Atlantic freshwater anomalies in preceding years
    https://doi.org/10.5194/wcd-5-109-2024
(8) Climate models underestimate the sensitivity of Arctic sea ice to carbon emissions
    https://doi.org/10.1016/j.eneco.2023.107012
(9) Sea Ice Trends in Climate Models Only Accurate in Runs with Biased Global Warming
    https://doi.org/10.1175/JCLI-D-16-0455.1
(10) Younger Dryas deglaciation of Scotland driven by warming summers
     https://doi.org/10.1073/pnas.1321122111
(11) Warm summers during the Younger Dryas cold reversal
     https://doi.org/10.1038/s41467-018-04071-5
(12) Drivers of exceptionally cold North Atlantic Ocean temperatures and their link to the 2015 European heat wave
     https://doi.org/10.1088/1748-9326/11/7/074004
(13) Impacts and State-Dependence of AMOC Weakening in a Warming Climate
     https://doi.org/10.1029/2023GL107624
(14) Changing European hydroclimate under a collapsed AMOC in the Community Earth System Model
     https://doi.org/10.5194/hess-29-6607-2025
(15) The absence of an Atlantic imprint on the multidecadal variability of wintertime European temperature
     https://doi.org/10.1038/ncomms10930
(16) Climate impacts of a weakened Atlantic Meridional Overturning Circulation in a warming climate
     https://doi.org/10.1126/sciadv.aaz4876
(17) Impact of the North Atlantic Warming Hole on Sensible Weather
     https://doi.org/10.1175/JCLI-D-19-0636.1
(18) Global and European climate impacts of a slowdown of the AMOC in a high resolution GCM
     https://doi.org/10.1007/s00382-015-2540-2
(19) Extreme cold events in Europe under a reduced AMOC
     https://doi.org/10.1088/1748-9326/ad14b0
(20) North Atlantic freshwater events influence European weather in subsequent summers
     https://doi.org/10.5194/wcd-2021-79



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