# US AMOC Science meeting notes

###### tags: `meetings` `ideas`
For references : https://usclivar.org/amoc

### Day 1
- Gokhan Danabasoglu
- Check out the **US AMOC reports** of 2013,14,16,18 and finally in 2022 at https://usclivar.org/us-clivar-reports
- 9 AGU special papers (https://agupubs.onlinelibrary.wiley.com/doi/toc/10.1002/(ISSN)1944-9208.AMOC)
- Meric Srokisz et al *commentary on these papers* (https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020JC016745)
- AMOC webinars (https://usclivar.org/amoc/amoc-webinar-series)
- Frontiers in Marine science papers for OCEAN Obs'19, Frajka Williams et al (https://www.frontiersin.org/articles/10.3389/fmars.2019.00260/full) and Kemper et al (https://www.frontiersin.org/articles/10.3389/fmars.2019.00065/full)
- **Major findings**
- AMOC downturn in 2009-2010 with impact on mid-latitude heat content.
- MOVE array at 16 N for measuring the southward flowing deep water. **Open question, the decadal trend not consistent with 26 N and only partially reporoduced by models. See Matthias Lankhorst's work**.
- *Frajka-Williams et al 2018* on MOVE and RAPID. *Danabasoglu et al 2021*
- OSNAP
- *Petit et al* on Deep water formation in Icealand basin, *Menary et al, Oldenburg et al , Yeager et al* on Labrador sea role in AMOC.
- SAMBA at 34.5 S since 2013
- AMOC in reanalysis products, *Laura Jackson et al 2019* and *Karspeck et al 2016* (also has ECCO analysis)
- Influence of winds : Mid-latitude winds dominate on seasonal mean and variability.
- Conceptual diagram in *Lynch-Stieglitz et al*
- Observing the AMOC : biggest challenge to build a sustained AMOC observing system.
- Move towards merging of observations, modeling and data assimilation towards more process based understanding.
- AMOC is better than sliced bread joke, what lol

- Susan Lozier
- Penny Holliday made the OSNAP schematic !
- This is where we justify the Iceland basin, Irminger seas importance.
- *Fu et al* upcoming
- *Zou et al 2020* looking at overturning in temperature and salinity space. **This helps in understanding the overturning in the labrador sea**.
- Mechanism of density compensation in the labrador sea. Extension of the 2-layer model of Streno 2006. *Bebieva and Lozier in prep*
- on the other hand GSR and OSNAP east variability : *Petit et al 2020*. Surface transformation and volume budget.
- *Majumdar and Lozier* in prep
- Optimization of OSNAP array :
- **Overturning in irminger and Iceland basin a major contributor to the AMOC**. Petit et al 2021
- **open questions**
- Is the ~ 6 years of OSNAP representative of MOC, MHT and variability on longer time scales ?
- How will the ice/glacial melt impact overturning in the coming years and the differential impact for OSNAP East and West.
- We still don't know the time scale for meridional coherance based on observations.
- How will changes in AMOC impact the uptake of anthro CO2 ?
- Why is there still a large spread in AMOC response among models ?

- Leah Chomiak
- Advective timsescales within the North Atlantic. via T/S signals (*why are we not doing this ?*).
- *Andres et al 2018, Bilo and Johns 2019 and Bower et al 2019*
- Hydrographic locations ; *Labrador sea , Line W , Abaco , Bermuda*
- *Chomiak et al* in prep : Neutral density framework
- *1987-1994 in Labrador sea was a big convective phase*.

- Wilbert Weijer
- Schematic !
- Wilbert's slides.
- *Smedsdrud et al 2022*
- There is not a one2one relationship between the AMOC at lower latitudes and the OHT into the Arctic.

- Laifang Li
- *Calling it the 'cold blob' rather than the 'warming hole'*
- *Li et al 2021*
- *Fan et al 2022* in prep on North Atlantic atmospheric circulation pattern
- *Li et al 2021* on 100 year trend in the North Atlantic storminess
- 2- box model of ocean heat balance ; *Gregory 2000, Held et al 2010 and Gupta and Marshall 2018*
- *Fan et al 2021* **on mechanisms of the cold blob in a modeling study**

- Andreas Schmittner
- Sediment data is carbon 13 (Peterson et al 2014), Radiocarbon data from Skinner et al 2017
- They look at fundamentally **the AMOC depth and AMOC strength, which is an interesting phase space to look at.**
- AMOC depth strongly affects southern ocean reservoir age.

- Nick Foukal
- **OSNAP, NOAC, RAPID, MOVE, TRACOS, SAMBA**
- **Recommendations for evaluations** :
- **Report overturning in density space** : Xu et al 2016** *STMW cell is neglected in depth space and density space AMOC stremanfuction contains more information for water mass transformation.*
- **Reference velocity shear to satellite altimetry** : *Sanchez-Franks et al 2021, McCarthy et al 2020*. Most OSSEs at RAPID have not tested ssh to references velocities, refs
- **Publish time series of compensation transports** : *Frajka-Williams et al 2018*. Helps give an idea on how much can we close the mass budgets.
- **Evaluate MHT and MFT in addition to MOC**
- **Compare OSSEs across multiple models** *Li et al 2017*.
- Use the entire AMOC observing system than just the arrays.

- Ben Moat
- RAPID in the canary islands in Bahamas
- MOC April 2004 to Feb 2020 : averaging over 10 day into 540 days. Next update in August 2022.
- Overturning stream function with depth plots.
- Largest contribution to AMOC variability is from mid ocean transport
- mid atlantic ridge contributes little to the AMOC variability
- largest signal is in the west.
- **Heat transport most variability is in overturning component with 96% of variance explained by the overturning at 26 N**
- **certain arrays removed from AMOC system. What happens then ? They are replaced with monthly climatology. mean is virtually 0 and the std is 0.07 Sv. However, removing data below 1500 m on the eastern boundary creates large errors.**
- BGC array deployed March 2022.
- 8 M euros project planned for 2022-27.
- **The RAPID array has been modified but has not brought any changes to the measurements. This has made the economic costs to come down to half !**
- Susan's concern on changing the method ? response on funding of these arrays. Have to look at alternatives. Can we get away from the emission part of the systems.

- Renellys C. Perez
- SAMOC began in 2007
- SAGA 2021 new program
- iAtlantic and TRIATLAS 2022 new program
- SAMBA pilot array : Meinen et al 2018 ; **mean 14.7 Sv and SD 8.3 Sv**
- Kersale et al 2020, 2021
- SAMOC history article coming up and science review article

- Franz Philip Tuchen
- *Bower et al 2019* for schematic.

- Femke De jong
- Irminger current variability.

- Tom Rossby
- *Oleander, Explorer of the seas* 38 Hz
- The longest time scale accessible to us hydrographically.
- The 2.5 Sv AMOC decrease manifests itself from change in slope water properties. They conjecture
- Robinson et al Science 2005
- SPG expands a lot in Glacial times.
- AMOC overturning slide 
- **We should call the subpolar overturning waters as NA Intermediate waters and let the Nordic seas be called the NA deep waters**
- 1937-1940 sections made by Isilin ?. 1940 paper !
- Paleo people look at the Nort Atlantic using the schematic that camera has. Would bring the two communities come together.
- station S started by Henri Stommel.

### Discussion
- **Is there a way to design a practical AMOC observing system ?**
*RP*: We can do tandem deployements of BPS, can also get ekman component from wind stress from satellites and reanalysis. Having Moored arrays scaled back over time but having what that looks like. *MS*: read papers where ocean models do a pretty good job when forced with reanalysis, if not for predictability then atleast for the history. *Steve*:yes on MS's point, has a poster on this, tomorrow. *GD*: Controversial, AMOC is not being declining over the same time period from observations as suggested by models. Details of methodology make a difference. He says from observations, you can't really say much. *RP*:some of these arrays are actually not constructed for AMOC, they are just being adopted for AMOC. *RDJ*:Fram strait, DSOW, can also benefit ??. *RP*What is the best way to measure AMOC variability between 10N-10S ? *TR*:Would it help to focus on just th Northward flowing

### Poster suggestions
- Liz Maroon suggested talking to jaime palter and papers about what's happening at the gulf stream near the grand banks.
- Femke suggested that we can show the state of the SPG in different years over the renske section.
- Who kim suggested he looked at something similar in his own paper. Look that up.

### Day 2

- Jon Robson (Mechanisms and predictability of AMOC)
- Schematic from *Johnson et al 2019*
- *Model based estimates suggest that surface forced variability dominates* : Germe et al 2022
- Role of surface forcing ; **Jackson et al 2022**, along with a whole range of papers
- Intrenannual variability : Role fo wind forcing , *Polo et al 2014 JPO*
- Implications for predictability : **If variability is largely wind-driven, then the predictability of the atmospheres circulation is the key** ; Hallam et al 2019
- **Decadal variability** 3 main contenders : **Buoyancy forcing** (Delworth and Feng 2016, Robson et al 2012, Yeager and D , 2014), **Rossby waves , wind forcing on decadal time scales**
- **Buoyancy forcing and role of NAO** : Xu et al 2019, Robson et al 2012. *NAO related buoyancy forced AMOC changes remains teh domincant paradigm to eplain decadal variability in SPNA*. However, in coupled runs, the spread is higher in the response. (Jiang et al 2021, Menary et al 2013, Lai et al 2022)
- Poster by Annika Reintges
- **Subsurface density anomalies and coherence of AMOC** : Ortega et al 2021, Yeager 2020. subpolar sub-surface density anomalies are key predictor for AMOC.
- **Predictability**: Little work. Skill very sensitive to model drift (Menary et al 2016). Also important is the initialzation of subsurface density anomalies key for predictions of upper ocean SPNA (Yeager 2020)
- **Role of external forcing** : Menary et al 2020
- **Ongoing questions and Challenges** : Megann et al 2021, Yeager et al 2020. Challenge to cosntrain the details of buoyancy forced variability.
- Who Kim's poster
- **Representation of AMOC in models problems**
- Mismatch between simulated and implied historical AMOC
- Still a large spread in rate of future AMOC declines across omdels (Weijer et al 2020)
- **Moving forward** Move to higher resolution coupled omdels (Roberts et al 2020, Yeager et al 2021). Constrain AMOC short term variability against observations.
- **Consistent and easy to apply analysis tools of key diagnostics** This is key
- Conclusion slide 

- Rong Zhang (Arctic and SPNA interactions)
- CMPI6 models exhibit large spread and uncertainities (Weijer et al 2020)
- **Zhang and Thomas, 2021**
- **RDC method** originally proposed in *Sarmieneto and Bryan 1982*, used in Zhang and Vallis , 2007
- *FS and BSO provid ethe densest source waters to AMOC*. You see this in the density space. Read the paper carefully !
- Schematic in the vertical also made. This might help Wenrui's or my later papers.
- *sigma-z diagrams designed to illustrate the horizontal gyre contribtion to density space AMOC*
- Summary slide 
- **IMP Side note : I want to make Wilbert's schematic from following all the papers that write about the circulations and then compare with the other schematics in the literature.**

- Jiayan Yang (Topographic influences on AMOC variability)
- 3 layer wind driven model ; Based on 2-layer model of Yang 2015
- Schematic in *Yang 2015, JGR Oceans*
- Zhai et al 2021 ?
- Summary slides 

- Marilena Oltmanns (Freshwater feedbacks in SPNA)
- cycle image in phone
- *Oltmanns et al* in prep **offers some insight into why the Arctic might be in the anti-cyclonic regime now for a lot of years**.
- Conclusion 

- Thierry Penduff (Atmospheric foreced and ocean driven interannual variability of AMOC)
- Upper cell of AMOC
- Based on *Leroux et al 2018*
- http://meom-group.github.io/projects/occiput/ for more information on this project
- OCCIPUT ensemble outputs are also available. *possibly might need this at some point?*

- Wei Lu (Climate impacts of a weakended AMOC in 21st century)
- CCSM4 sensitivity experiment, RCP8.5, 5 ensemble members, sensitivity experiments with fixed AMOC and hist+RCP8.5 forcing
- *Liu et al 2020*
- *Ren and Liu 2021*

- Fiamma Straneo (AMOC and ice)
- **Can AMOC variability drive changes in ARctic sea ice or in GIS ?**
- Arctic report card 2021
- Where the sea ice is changing ;*Onarheim et al 2008*
- Spreading of Atlantic water in the Arctic ; *Timmermans and Marshall, 2020*
- Atlantification of the Barents Sea ; *Arthun et al 2012*
- Atlantification of the Eurasian basin ; *Polyakov et al 2017*
- Multidecadal and lon-term AMOC and sea ice ; *Delworth et al 2016*, *Arthun et al 2019*
- **Rising air temperatures and ocean temperature** are thus two ways
- Heat transport to the margin of glaciers
- Air temperatures
- *Noel et al 2022* Icealand's glaciers and north Atlantic cooling
- *Iceland glacier meling . Surface melt correlated to surface temperature > related to heat transport anomalies*
- *increased heat transport to glaciers > increased submarine melting > retreat of glaciers*
- Investigating ice loss to atmospheric and ocean forcing ; *Slater et al 2019, 2020*

- Qian Li (Impacts of Greenland and Antarctic Glacial melt)
- Bed Machine data for land ice thickness. *This dataset seems interesting !*
- Asymmetric response of the AMOC to greenland and antarctic glacier melting. Why ?

- Seung Hun Baek (AMV)
- **What processes communicate SPA SST change to tropical NA ?** answer using idealized models
- *Baek et al 2021* ; warm and cold phases of AMV are asymmetric.
- Asymmetry in fully coupled models.

- Tom Delworth (Weakended AMOC linked to drying Mediterranean)
- Take home
- If the GHGs decline, even then winter MD precip declines
- Decline after 21st century does not induce precip recovery
- SSP534OS > CO2 and CH4 decline after mid-century.
- AMOC in this case has little to no recovery
- For the OS scenario, in *summer* precip recovers, while in winter it does not
- since the summer and winter time response qualitatively look similar, how big is the role of ensemble averaging in percieving this winter time response ?
- Mechanism
- enhanced sea icea and cooling in SPNA
- deep anomalius cyclonic atmospheric circulation
- anticyclonincover MD
- They perform sensitivity analysis to test for robustness

- Emma Levin (Tropical cyclones and AMOC)
- TC Genesis reduced in northern hemisphere and in different basins

- Jeremy Klavans ()
- **NAO and AMV are happily married until 1950 (r=0.62) and then divorce (r=0.06)**. *Proposing that mechanisms changed.*
- *Delworth et al 2017* for mechanisms ; **NAO, AMOC, external forcings**
- *Klavans et al 2022*
- NAO-AMV responding to external forcing
- discussion on camera
- Rong's comment on that AMV time series should have been detrended !

How to access recordings, for Tom

### Day 3

- Paola Moffa-Sanchez (review of paleo AMOC)
- *Curry and Mauritzen 2005* schematic of the AMOC
- *Thornalley et al 2018* for AMOC surface fingerprints.
- *Moffa-Sanchez et al 2019* schematic of the currents in North Atlantic.
- Progress in the last few decades in camera
- *Role of the AMOC in glacial-interglacials* ; Barker et al 2011
- **AMOC in the holocene**
- High resolution archives : Tree rings, ice-cores, polen
- Mayeski et al for review
- Conceptual diagrams of AMOC from *Lynch-Stieglitz 2017*.
- Subsurface temperature contrast between the gulf stream and subpolar gyres based on Zhang 2008 fingerprint.

- David Thornalley (Holocene Atlantic overturning)
- sortable silt grain size to reconstruct ISOW flow speed.
- Reconstruction of DSOW too !
- How wsa the GSA related to the end of the ice age ?
- Does the DSOW show any relaionships with the sea ice export apart from the nordic sea circulation ?

- Feng he (Freshwaer forcing on AMOC Paleo)
- *He and Clark 2022* ; Why does the AMOC not show sensitivity to FW flyxes associated with the North H glaciation ? It does go down but up again ...

- Yvean Rome

- Wanyi Lu (Little ice age cooling and 20th century warming in deep atlantic sediments)

- Shanton sun
- Sun et al 2020 and Sun 2022
- Overturning circulation in a reduced gravity model. Basically Anand's 1999 paper.
- Provides update to the bipolar seesaw ?
- stsun.github.io

Tom Delworth's suggestion on a paper about the AMOC and is it weakening ? This is a BIG challenge in the context of public perception.

- Martha Buckley (SPNA SST variations)
- *Jackson et al 2021*
- Why is there a deep overturning in the Atlantic ; *Cessi, 2019*
- *Cessi et al 2019* plots the overturning in density coordinates using ecco data
- Overturning streamfunctions in temperature coordinates. Helps to think about ocean heat transport. Described in *Ferrari and Ferreira 2011*. This is what they were talking about when we were thinking about the conceptual model.
- Using the model experiment, **60% of heat transport is because of a circulation that extends from thermocline to mid-depth**.
- Separating the effects of tiem variable wind and buoyancy forcing ; *Larson et al 2018, 2020* **Important papers**
- Meridional coherance of AMOC strength diagrams, *Boning et al 2006*
- Barotropic streamfunction variance is another good metric
- Yeager 2015 talks about coupling by bottom pressure torques between the wind driven and overturning circultion
- *Jackson et al 2022* also has decadal variations in SPNA SST
- See also *Foukal et al 2018, Yeager 2020*
- See camera
- See Lauri Trenary's poster
- There are mechanisms that don't invoke the AMOC or the horizontal circulation. Predictability is also done using MLD. This is Glenn Lui's poster.
- Divergence of heat north and south all the way to antarctica. suggests Gael Forget. Also Helmoltz decomposition ; Rotational from the divergent component, Gael's paper from 2019.

- Chris Piecuch (Florida current)
- Florida current participates in the AMOC. best observed current *Volkov et al 2020, Meinen et al 2010*
- **Bayesian heirarchical modeling separate the common signal from noise inherent to each dataset.**
- Summary slide in camera
- **inference on a decline in transport is robust.** Discussion should be lit.

- Dan Amrhein (dominant drivers of interannual AMOC variability)
- *Moat et al 2020*
- *Stephenson and Sevellec 2021*
- Adjoint sensitivities. *Kostov et al 2019, 2021 Fukumori et al 2021*
- Wolfe et al 2017 spun up ECCO v4 under 4800 years !
- *Fukumori et al 2021*
- Conclusion in camera, IMP
- Adjoint of CMIP6 models ?

- Olivia Gozdz
- Met her at GMU ESOM !

### Discussion
MS:What would you need to observe to find if AMOC is at a tipping point ? WW:Salt advection feedback, in the nordic seas. GD:But this is coming from box models, but in reality so much more is happening, so you can't really say. TR : no evidence that shallow overturning is shutting down. Me thinking : Can we think about this question in terms of OSSEs ? TR : These are also gradual decreases. CP:How can we also think about other climate relevant measurements when it comes to what should we measure ?

*idea* : Learning about OSSE's isn't OceanSpy the best thing to do OSSE's !!

### Future directions

**International CLIVAR task team **
- Next meeting soon. on observing systems requirements. OSSEs ! we should apply to this. Possible applications of oceanspy
- OceanSites: include AMOC data distribution
- 

*idea* : AMOC CMIP tools as suggested by Jon Robso, possibly a great pangeo project

#### Impressions

- Spoke to Nick Foukal regarding a bunch of things, but what struck was his career advice and being open about possible options outside of academia. Also, his advice on how to look at possible postdoc advisors and how to think about applications.
- Interacted with Femke and Gael Forget about advisors and ECR options and how to go about thinking about it.
- some folks that made really positive impressions ; Gokhan D, Susan Lozier, Wilbert Weijer, Mike Spall, Tom Rossby, Tom Delworth, Dan Arnheim, Chris Piecuch, Glenn Liu, Gaurav, Veronica