#uöäü1AMOC
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Now we have the next model result on the #AMOC

Could be stable till the end of century

Only nuisance is that current models can't simulate the AMOC

But they mention it so may it be forgiven

#climate #uöäü1AMOC
Continued Atlantic overturning circulation even under climate extremes - Nature
Climate models suggest that the Atlantic Meridional Overturning Circulation is unlikely to collapse this century, owing to stabilization from wind-driven upwelling in the Southern Ocean.
www.nature.com
February 26, 2025 at 5:34 PM
umsonst.bsky.social
New studies question if measurements near Florida can be used for Gulf Stream/AMOC strength

Further, the water inflow above Norway has increased the last decades but not its energy transport- more mixing with subpolar waters

AMOC collapse soon I do not see it...

#climate #uöäü1AMOC #uöäü1arctic
Unsere Erde - in Theorie, Beobachtungen und Projektionen
New studies question if measurements near Florida can be used for Gulf Stream/AMOC strength As it seems a signal from one location is not necessarily passed on to the north as each gyre transport...
www.facebook.com
July 16, 2024 at 12:30 PM
umsonst.bsky.social
While all go AMOC the real change happens on the other side of our planet - somehow strange...

"A large-scale readjustment of the GMOC seems to be underway in the South Atlantic and Indo-Pacific Oceans since the mid-2000s in response to the Southern Ocean changes."

#climate #uöäü1AMOC #AMOC
In a warming climate, the Global Meridional Overturning Circulation (GMOC) is expected to change significantly with a risk of disrupting the global redistribution of ocean properties that sustains marine ecosystems, carbon cycle, and others. Here we make a novel attempt to utilize a diagnostic ocean & sea-ice model to estimate the GMOC and its interdecadal changes since the mid-1950s that are consistent with historical hydrographic observations. We find that significant changes in the GMOC have already occurred, most notably in the upper and lower overturning cells in the Southern Ocean. The former has expanded poleward and into denser water and strengthened by 3–4 Sv since the mid-1970s, while the latter has contracted and weakened by a similar rate during the same period. These changes are driven by the increasing Southern Hemisphere (SH) Ferrel cell and associated increases in the westerlies and the surface buoyancy loss over its sinking branch, and the increasing Antarctic meltwater discharge, in response to ozone depletion in the SH stratosphere and increasing atmospheric CO2. A large-scale readjustment of the GMOC seems to be underway in the South Atlantic and Indo-Pacific Oceans since the mid-2000s in response to the Southern Ocean changes. "Human-induced changes in the global meridional overturning circulation are emerging from the Southern Ocean"; https://www.nature.com/articles/s43247-023-00727-3#Fig6 This suggests that the large increase in the AMOC at 55°N in 1995–2004 is a delayed response to a strong phase of the NAO in 1985–1994, which is closely tied to the deepest and densest Labrador Sea Water formed during that period56 (Fig. 3). Similarly, it is likely that the relatively weak AMOC transport at 55°N during the decades prior to and after 1995–2004 are due to the relatively weak NAO phases and associated reductions in Labrador Sea Water formation prior to 1985–1994 and after 1995–200456. These results suggest that the AMOC changes at 55°N during the past several decades are not externally forced by increasing greenhouse gases but largely modulated by long-term natural climate variability associated with the NAO52,53. Indeed, similar interdecadal AMOC variations are also evident at 26.5°N and 30°S (Fig. 3b). This conclusion is also consistent with several recent studies based on various proxies, historical transects and ocean reanalyses43,57,58,59, including two recent AMOC reconstructions for the past 30 years58,59. Therefore, it is likely that the previously reported weakening of the AMOC at 26.5°N during 2008–2016 compared to its value during 2004–200722 is due to long-term natural climate variability associated with the NAO. buoyancy loss/gain - gets denser (colder/saltier), wants to sink, gets less dense (warmer/fresher) does not want to sink Anthropogenic drivers for the Southern Ocean The strengthening and poleward-downward expansion of the upper overturning cell south of 35°S is consistent with the strengthening SH westerlies and the associated increase in Ekman transport since the mid-1970s (Fig. 4 in the left panels), which is primarily caused by ozone depletion in the SH stratosphere and increasing CO2 in the atmosphere32,33,34,35,36. However, the increased Ekman transport alone cannot sustain the strengthened upper overturning cell. There must be additional surface buoyancy loss and associated water mass transformation66,67. Otherwise, the increased Ekman transport is almost completely compensated by eddy-induced poleward transport in the Southern Ocean (i.e., eddy compensation38,39,40,41). The required additional pulling of the upper overturning cell is mainly provided by reduced precipitation minus evaporation (i.e., Δ(P − E) < 0)68,69 and associated surface buoyancy loss across the sub-Antarctic region approximately between 50°S and 35°S (Fig. 4 in the left panels). More specifically, the net buoyancy loss in the latitude band of approximately 45°S − 35°S is largely accomplished by a decrease in precipitation, and an increase in evaporation and associated latent cooling (Fig. 5b, c). These buoyancy loss terms overcompensate the buoyancy gain associated with reduced sensible heat flux and increased longwave radiation.
November 20, 2024 at 4:45 PM
umsonst.bsky.social
Here a preprint on Subpolar North Atlantic (SPNA) salinity changes and #AMOC :

"It's worth noting that no significant salinity trend was observed in the SPNA, implying the stability of deep water formation in recent decades."

#climate #Arctic #uöäü1AMOC
January 26, 2025 at 3:55 PM
umsonst.bsky.social
Another #AMOC data point:

In the 2012 we had the largest freshwater impulse from the Arctic Ocean into the subpolar North Atlantic. Now studies coming out analyzing the effect.

Tells us a lot about AMOC stability. Some effect it had on deep water formation, so much is clear

#climate #uöäü1AMOC
Figure description and later their findings Schematic overview of the circulation in the Irminger Sea and hydrography of the Irminger Current. (a) Schematic main currents in the Irminger Sea: Irminger Current (IC), East Reykjanes Ridge Current (ERRC) and East Greenland Current (EGC) and bathymetric features: Bight Fracture Zone (BFZ) and Reykjanes Ridge. What they found out: Starting in 2012, the eastern subpolar North Atlantic experienced the strongest surface freshening in the past 120 years. It is yet unknown whether this salinity anomaly propagated downward into the water column and affected the properties of the boundary currents of the subpolar gyre, which could slow down the overturning. Here, we investigate the imprint of this salinity anomaly on the warm and saline Irminger Current (IC) in the decade thereafter. Using daily mooring data from the IC covering the period 2014–2022 combined with hydrographic sections across the adjacent basins from 1990, the evolving signal of the salinity anomaly over the water column and its imprint on the transport variability is studied. We find that due to the salinity anomaly, the northward freshwater transport of the IC increased by 10 mSv in summer 2016 compared to summer 2015. In 2018, the salinity anomaly covered the water column down to 1,500 m depth. Hydrographic sections across the basin showed that this recent freshening signal spread across the Irminger Sea. Overall, the freshwater transport of the IC increased by a factor of three between 2014–2015 and 2021–2022. The associated density decrease over the upper 1,500 m of the water column resulted in an increase in the northward transport of waters lighter than σ0 = 27.55 kg m−3 from 1.7 to 4.2 Sv. This change in northward IC transport by density class may impact the characteristics of the overturning in the Northeastern Atlantic, its strength and the density at which it peaks. Salinity evolution at IC2, IC4, and M1 Daily salinity anomalies from IC2 (a), IC4 (b) and M1 (c) mooring (shading) overlaid with potential density (contours). The anomalies are computed by removing the 2014–2022 mean salinity and seasonal cycle at each location and depth. Horizontal black lines mark instrument depths for respective deployment periods. Annual mean salinity anomalies for IC array from 2014 to 2022 Salinity anomalies from summer to summer for the IC referenced to the mean salinity over 2014–2022 (color) with yearly mean isopycnals. Black triangles at the surface mark the IC boundaries. Black vertical lines mark the mooring locations. Contribution of temperature and salinity to the density anomaly time series of the density anomaly over the entire IC related to salinity (orange), temperature (green), the sum of both (total, black), and the observed (gray) in kg m−3. The density anomalies are computed by linearizing the equation of state between the IC boundaries (black triangles Figures 1b and 1c) relative to the 8-year mean over the whole water column (see Supporting Information S1).
January 26, 2025 at 3:25 PM
umsonst.bsky.social
Another argument for a weakening AMOC:

"The increase in Agulhas Leakage is accompanied by a higher salt flux into the Atlantic Ocean, which suggests a destabilisation of the AMOC by salt-advection-feedback."

egusphere.copernicus.org/preprints/20...

#climate #uöäü1AMOC
Long-term Variability and Trends of Agulhas Leakage and its Impacts on the Global Overturning
Abstract. Agulhas Leakage transports warm and salty Indian Ocean waters into the Atlantic Ocean  and as such is an important component of the global ocean circulation. These waters are part of the upp...
egusphere.copernicus.org
October 20, 2024 at 5:27 PM
umsonst.bsky.social
#AMOC slow down can trigger massive methane hydrate destabilization as currents shift

"Evidence for massive methane hydrate destabilization during the penultimate interglacial warming"; www.pnas.org/doi/full/10....

#climate #uöäü1methane #uöäü1AMOC
Evidence for massive methane hydrate destabilization during the penultimate interglacial warming | PNAS
The stability of widespread methane hydrates in shallow subsurface sediments of the marine continental margins is sensitive to temperature increase...
www.pnas.org
December 3, 2024 at 12:47 PM
umsonst.bsky.social
New studies question if measurements near Florida can be used for Gulf Stream/AMOC strength

www.facebook.com/Erdsystemfor...

#climate #uöäü1AMOC #uöäü1currents #uöäü1OHC
Unsere Erde - in Theorie, Beobachtungen und Projektionen
New studies question if measurements near Florida can be used for Gulf Stream/AMOC strength As it seems a signal from one location is not necessarily passed on to the north as each gyre transport...
www.facebook.com
July 16, 2024 at 3:22 PM
umsonst.bsky.social
Next study that does not see a weakening of the AMOC in our measuring record. Only before our measurements had started

Since 2010s the signal reversed and AMOC gained in strength again (positive NAO). Likely, this will continue for the next years

#climate #uöäü1AMOC #AMOC
A pause in the weakening of the Atlantic meridional overturning circulation since the early 2010s
The current state-of-the-art climate models suggest that the anthropogenic weakening of the Atlantic Meridional Overturning Circulation (AMOC) has already begun since the mid-1980s. However, direct ob...
www.researchsquare.com
November 23, 2024 at 3:58 PM
umsonst.bsky.social
Next #AMOC study that it was not weakening the last decades

This part of the overturning circulation could be more stable than some model experiments suggest

After a phase of strengthening we seem to enter just now again a phase of weakening

Start of the trend?

#climate #uöäü1AMOC
Atlantic overturning inferred from air-sea heat fluxes indicates no decline since the 1960s - Nature Communications
The AMOC is crucial for&nbsp;the global ocean overturning circulation and controls the climate around the North Atlantic. Here, the authors use 24 Earth System Models from the CMIP6 to demonstrate tha...
www.nature.com
January 16, 2025 at 7:52 AM
umsonst.bsky.social
Meltwater release of the Beaufort Gyre is one of the main mechanism discussed to impact AMOC circulation. Now a new interesting paper came out so I connected the dots

Just a possibility of a chain reaction related to sea ice loss in the Arctic

#climate #uöäü1AMOC #uöäü1SIC #uöäü1feedback
A short on a possible mechanism for AMOC collapse
Woods Hole; https://www.whoi.
www.linkedin.com
September 22, 2024 at 12:04 PM
umsonst.bsky.social
Cold blob in the subpolar NA has not developed till now, which is seen as a proxy for AMOC strength

The North Atlantic cold blob forms when less cooled water at the surface sinks down

Added a critique on the cold blob theory. Only strong AMOC decline causes cold blob

#AMOC #climate #uöäü1AMOC
Observed fingerprint of a weakening Atlantic Ocean overturning circulation (2018) "Here we provide evidence for a weakening of the AMOC by about 3 ± 1 sverdrups (around 15 per cent) since the mid-twentieth century. This weakening is revealed by a characteristic spatial and seasonal sea-surface temperature ‘fingerprint’—consisting of a pattern of cooling in the subpolar Atlantic Ocean and warming in the Gulf Stream region. [...] The pattern can be explained by a slowdown in the AMOC and reduced northward heat transport, as well as an associated northward shift of the Gulf Stream. Source: "Observed fingerprint of a weakening Atlantic Ocean overturning circulation"; https://www.nature.com/articles/s41586-018-0006-5 Key Points Sea surface temperature based fingerprint of Atlantic Meridional Overturning Circulation (AMOC) changes under different forcing scenarios AMOC in steep decline significantly contributes to North Atlantic warming hole formation, largely due to cloud radiative forcing AMOC plays a smaller role in North Atlantic SST variability in historical period and after CO2 stabilization than during significant warming "Nonstationarity of the Atlantic Meridional Overturning Circulation's Fingerprint on Sea Surface Temperature"; https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2024GL109789
November 23, 2024 at 4:22 PM
umsonst.bsky.social
Here is the study: maybe till now the most important signal and it will give us a better idea of how robust the AMOC is against freshwater outbreaks: www.nature.com/articles/s43... #AMOC #uöäü1AMOC #climate
Intensification and shutdown of deep convection in the Labrador Sea were caused by changes in atmospheric and freshwater dynamics - Communications Earth & Environment
After intense winter cooling 2012-2015, Labrador Sea convection continued to intensify to 2018, and subsequently weakened and shoaled due to polar vortex collapse and Arctic sea ice loss, as analyses ...
www.nature.com
November 23, 2024 at 4:11 PM
umsonst.bsky.social
Next study that an #AMOC collapse is unlikely this century as Southern Ocean upwelling of Atlantic waters has also to stop and in the NP a compensating deep convection has to start

Is the AMOC discussion a broken sci. discussion?

#climate #Earth #uöäü1AMOC
January 6, 2025 at 7:37 AM
umsonst.bsky.social
#AMOC details on mixing:

Isopycnal stirring is found to account for the majority of thermal (65%) and haline (84%) variance dissipation in the upper 400 m of the eastern SPNA.

#climate #uöäü1AMOC
Isopycnal Eddy Stirring Dominates Thermohaline Mixing in the Upper Subpolar North Atlantic
The Atlantic Meridional Overturning Circulation entails vigorous thermohaline transformations in the subpolar North Atlantic Ocean (SPNA). There, warm and saline waters originating in the (sub)tropic....
agupubs.onlinelibrary.wiley.com
January 21, 2025 at 9:22 PM
umsonst.bsky.social
#AMOC just for the record: "A pause in the weakening of the Atlantic meridional overturning circulation since the early 2010s"

My bet: till the AMOC breaks down not many of us will be left to witness it

So many feedbacks now rolling on, while we still increase emissions

#climate #uöäü1AMOC #Earth
A pause in the weakening of the Atlantic meridional overturning circulation since the early 2010s - Nature Communications
The anthropogenic weakening of the Atlantic Meridional Overturning Circulation has begun since the mid-1980s. However, a tug-of-war between the natural and anthropogenic signals led to a near stalling...
www.nature.com
December 17, 2024 at 10:03 PM
umsonst.bsky.social
High resolution of the surface currents across the North Atlantic

"Ocean Currents Resolved on Regional Length Scales"; physics.aps.org/articles/v17...

#AMOC #Climate #uöäü1AMOC
Currents, of the North Atlantic in low and high resolution. Its a nice example of the complexity we are talking here...
November 24, 2024 at 9:49 AM
umsonst.bsky.social
#Arctic Freshwater content of the Beaufort Gyre: "in the Beaufort Gyre region of the Arctic Ocean document
an increase of more than 6,400 km 3 of liquid freshwater content from 2003 to 2018: a 40% growth relative to
the climatology of the 1970s" #climate #uöäü1AMOC
Analysis of the Beaufort Gyre Freshwater Content in 2003–2018
Beaufort Gyre freshwater content time series (2003–2018) from different data sets are updated, compared, and analyzed Qualitative and quantitative estimates of factors and mechanisms driving freshw...
agupubs.onlinelibrary.wiley.com
January 29, 2025 at 3:56 PM
umsonst.bsky.social
The brief (2010s) restrengthening period of the #AMOC could have ended

"The annual mean AMOC in 2022 is the lowest after its biggest drop in 2009" ocean2climate.org/2024/09/28/t...

#climate #uöäü1AMOC
The annual mean AMOC in 2022 is the lowest after its biggest drop in 2009
Scientists have been monitoring the Atlantic Meridional Overturning Circulation (AMOC) at around 26.5°N since April 2004 through the RAPID/Meridional Overturning Circulation and Heatflux Array/West…
ocean2climate.org
January 12, 2025 at 4:26 PM
umsonst.bsky.social
Interesting data point:

In 2007, a large number of bottles were found in Norway, coinciding with a contracted North Atlantic Subpolar Gyre during 2004-2008. While between 2012-2016, the majority of bottles were recovered on the British Isles, during a time of gyre expansion

#ocean #AMOC #uöäü1AMOC
Frontiers | Drift bottle data hint at large-scale ocean circulation changes
Over the last two decades, in an effort to engage youth in polar science, the Students On Ice (SOI; https://studentsonice.com/) project has become a platform...
www.frontiersin.org
January 26, 2025 at 6:29 PM
umsonst.bsky.social
#AMOC slow down slows down global warming by 20%

Reasons a weaker warming/cooling of the Arctic regions and a less positive cloud feedback, especially over the North Atlantic.

eartharxiv.org/repository/v...

#climate #uöäü1AMOC
Contribution of AMOC Decline to Uncertainty in Global Warming via Ocean Heat Uptake and Climate Feedbacks
eartharxiv.org
December 29, 2024 at 11:38 AM