Will the #AMOC collapse by 2025?
Here's what we know from direct observations (since 2004). A thread.
Image from Srokosz & Bryden (2015) https://shorturl.at/ryB34
1/11
The #AMOC is highly variable. More variable than scientists expected when the observations began.
2/11
Atmospheric variability can 'imprint' on the #AMOC strength.
We expected that cooling would matter, but find out that wind also matters didn't fit our classical view of the AMOC as a slowly varying circulation.
Jackson et al (2022) sums it up (https://shorturl.at/dnFY6)
3/11
The #AMOC can temporarily reverse. In 2009/10 and again later, the northward heat flux of the AMOC stopped and even reversed.
Temporarily! (These reversals were due to changing winds.)
McCarthy et al. 2012 (https://shorturl.at/adgiM)
4/11
Metrics for the strength of the #AMOC at different latitudes give different numbers.
On the one hand, this is unsurprising. The AMOC is a system of currents (not the #GulfStream). But it does complicate the picture compared to a simple 'conveyor belt'.
Frajka-Williams et al. (2019) https://shorturl.at/tFW49
5/11
The latest study (https://shorturl.at/fqyO8) is based on a statistical analysis of SST fingerprints not #AMOC measurements (remember, only available since 2004). It cites increases in variability as indicating that the system is moving towards a tipping point.
6/11
Statistical tools can be helpful, but run the risk of over-simplifying relationships in the climate system (i.e., how the #AMOC responds to freshwater, or the net effect of small-scale eddies on large-scale circulation).
Johnson et al. 2019 (https://shorturl.at/qMW28)
7/11
More complex models don't necessarily represent those relationships either. On account of models missing key processes, the IPCC AR6 report reduced confidence to medium (50%) that the #AMOC won't collapse by 2100.
IPCC AR6 WG1 Chapter 9 Executive summary (2021)
8/11
Scientists gathered in Hamburg to discuss the state of #AMOC research and observations. From the observational record, a majority agreed that we don't yet know how the AMOC will respond to future anthropogenic change.
#AMOC2023 #CLIVAR https://shorturl.at/adewO
9/11
Summary report in progress.
Sneak peak--we need:
- to reconcile missing key processes
- new approaches for basin-scale #AMOC understanding and,
- compound impacts of AMOC with carbon and cryosphere
- better articulation of societal impacts
Maybe education too. AMOC is not the #gulfstream
10/11
See also the Horizon Europe #EPOCproject where we dive deeper into #AMOC proxies, high resolution coupled modelling for missing key processes, latitude-spanning (34°S to Arctic) approaches, and new sensors for carbon/AMOC transports.
11/11
@EleanorFrajka thanks for this. Do scientists ever feel gut instincts about their work despite the evidence? What are the gut instincts about the AMOC?
@oneloveoneplanet
Of course they do: scientist are human! In fact, a lot of scientific training amounts to discovering in very fine grained detail how you can trust your gut feeling about how things work.
In the case of the AMOC, my impression is that Frajka-Williams is firmly in the "leave the gut out of it" camp.
@EleanorFrajka
@tobychev That's why I was asking; I'd like to know if there's a difference between the two.