EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Atlantic Salinity Pileup as a Remote Fingerprint of Weakening Atlantic Overturning Circulation under Anthropogenic Warming

Chenyu Zhu1,2,3 and Zhengyu Liu3
Chenyu Zhu and Zhengyu Liu
  • 1Peking University, Department of Atmospheric and Oceanic Sciences, China (
  • 2Open studio for Ocean-Climate-Isotope Modeling, Pilot National Laboratory for Marine Science and Technology (Qingdao), China
  • 3Atmospheric Science Program, Department of Geography, Ohio State University, USA

Climate models show a weakening Atlantic meridional overturning circulation (AMOC) under global warming. Limited by short direct measurements, this AMOC slowdown has been inferred, with some uncertainties, indirectly from some AMOC fingerprints locally over the subpolar North Atlantic region. Here we present observational and modeling evidences of the first remote fingerprint of AMOC slowdown outside the North Atlantic. Under global warming, the weakening AMOC reduces the salinity divergence and then leads to a remote fingerprint of “salinity pileup” in the South Atlantic. Our study supports the AMOC slowdown under anthropogenic warming and, furthermore, shows that this weakening has occurred all the way into the South Atlantic.

How to cite: Zhu, C. and Liu, Z.: Atlantic Salinity Pileup as a Remote Fingerprint of Weakening Atlantic Overturning Circulation under Anthropogenic Warming, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3790,, 2020

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Display material version 1 – uploaded on 01 May 2020
  • CC1: Comment on EGU2020-3790, David Smeed, 06 May 2020

    Thank you for presenting your work, it is interesting,.   On slide 5 of your presentation, "Trends of zonal mean salinity", over what time window were the trends evaluated?

  • AC1: Comment on EGU2020-3790, Chenyu Zhu, 06 May 2020

    Hi David,

    Sorry for not being clear in the presentation. The time windows are: observation (EN4) 1950-2017; CMIP5 "historical" 1950-2017; CMIP5 RCP4.5 2018-2100. 


  • CC2: Comment on EGU2020-3790, HAO LIU, 06 May 2020

    Hi, Chenyu

    Very interesting work! I was wondering (1) how you calculate the upper 300m transport of the AMOC in your slide 10? Does the zonal integral include just the western current, or basinwide?   (2) I am confused on one point that in your prediction of AMOC slowdown, your observations on the strength of the AMOC focused on low latitude in the North Atlantic ocean, but others report that the in the high latitude of NA, the strength of AMOC bounce back. Does your prediction show any strength of the AMOC increase in the near future in any latitude in NA?

    Best , Liu Hao

  • AC2: reply to HAO LIU, Chenyu Zhu, 06 May 2020

    Hi Hao,

    Here are my replies to your questions:

    (1) the transport is basinwide integal. I think integal along western boundary (which is more relevant to AMOC) will give the same trend signal since in all of our runs using ocean alone model forced by CORE-II datasets, the surface winds are fixed.

    (2) there are limited AMOC measurements. 26.5N RAPID array shows recovery after sharp decline around year 2010. The previous AMOC fingerprints, however, are all confined in the North Atlantic subpolar region which may bare large local variability such as AMO. Our new AMOC indice comes from South Atlantic and thus is not intended to predict AMOC in NA. Or in other words, the SA salinity index gives the meridionally coherent part of AMOC changes. It is interesting to note that AMOC variability shows some meridional incoherence in models which is thought to be induced by winds(Bingham et al. 2007;Biastoch et al. 2008a ). 

    Best, Chenyu