...that the A(MOC) is indeed strengthening and transporting more heat polewards. As expected in a warming world.
The science seems not settled on this yet but again the above mentioned Assessments claim otherwise: at least if you look at longer time periods (on the "controversy" see for example the comment from Mike Mann, linked by Susan Anderson on the recent RC article).
But more importantly: You may be expecting that the AMOC will strengthen in a warmer world. Climate scientists do not though .
The 4th US National Climate Assessment for instance has this to say:
Though observational data have been insufficient to determine if a long-term slowdown in the AMOC began during the 20th century, one recent study quantifies a 15% weakening since the mid-20th century and another, a weakening over the last 150 years. Over the next few decades, however, it is very likely that the AMOC will weaken. (my bold)
S.Pansa, the bolded statement at the end of your quote is exactly where I disagree. The AMOC might well have weakened in a longer historic perspective, but there is quite a few reports that indicate that it's currently strengthening. For completeness, I provide a list of papers here.
1. "On freshwater fluxes and the Atlantic meridional overturning circulation", by Cael and Jansen, january 2020
From the Abstract: "Our results robustly suggest that for the equilibrium state of the modern ocean, freshwater fluxes strengthen the AMOC..."
https://aslopubs.onlinelibrary.wiley.com/doi/full/10.1002/lol2.101252. "Indian Ocean warming can strengthen the Atlantic meridional overturning circulation. Nature Climate Change, in press (September 2019)., Hu, S., and Fedorov, A.V.
From Abstract: "Here, we describe how a salient feature of anthropogenic climate change – enhanced warming of the tropical Indian ocean (TIO) – can strengthen the Atlantic meridional overturning circulation (AMOC) by modulating salinity distribution in the Atlantic (Hu and Fedorov 2019). "
https://agu.confex.com/agu/osm20/meetingapp.cgi/Paper/649185The big issue is, where are those freshwater pulses going to come from that might trigger those tipping points? I don't see enough of Greenland glacier melt-off for that during the coming decades. And the volume of freshwater in the lens on top of the Arctic won't be enough, supposedly.
Furthermore, the theory isn't even settled, as this quote from paper 1. shows: "Our results robustly suggest that for the equilibrium state of the modern ocean, freshwater fluxes strengthen the AMOC, in the sense that an amplification of the existing freshwater flux‐forcing pattern leads to a strengthening of the AMOC and vice versa. A simple physical argument explains these results: the North Atlantic is anomalously salty at depth and increased freshwater fluxes act to amplify that salinity pattern, resulting in enhanced AMOC transport."
Thus, the question remains completely unsettled, both empirically and theoretically.
3. "Surface predictor of overturning circulation and heat content change in the subpolar North Atlantic" by Desbruyères et al.
https://os.copernicus.org/articles/15/809/2019/2019, Ocean Sci., 15, 809–817
They clearly demonstrate that the AMOC is currently strengthening, and they even give a bold forecast for the coming years:
"An easily observed surface quantity – the rate of warm to cold transformation of water masses at high latitudes – is found to lead the observed AMOC at 45∘ N by 5–6 years and to drive its 1993–2010 decline and its ongoing recovery, with suggestive prediction of extreme intensities for the early 2020s."
AMOC is forecasted to have "extreme intensities" in the coming years, as the AMOC is 'downstream' with a lag of 5 to 6 years from the already intensified warm to cold transformation of water masses at high latitudes.
4. "Pending recovery in the strength of the meridional overturning circulation at 26° N"
https://www.researchgate.net/publication/338658885_Pending_recovery_in_the_strength_of_the_meridional_overturning_circulation_at_26_Nby Moat, Smeed et al, Jan 2020
This is by the guys who actually 'run' the RAPID array.
5. "The North Atlantic Ocean Is in a State of Reduced Overturning", Jan 2019
by Smeed et al
https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2017GL076350From the conclusions:
"Our results show that
the previously reported decline of the AMOC (Smeed et al., 2014) has been arrested, but the length of the observational record of the AMOC is still short relative to the time scales of importantdecadal variations that exist in the Atlantic. Understanding is therefore constantly evolving.
What we identify as a changed state of the AMOC in this study may well prove to be part of a decadal oscillation superposed on a multidecadal cycle"
What they say in the last sentence is that all this is probably due to natural variations. Which is to be expected, as the AMOC, as well as its Pacific Ocean counterparts, eg. the PDO, have overturning times that are multi-decadal.