Reanalysis of the AMOC
Lead Research Organisation:
University of Reading
Department Name: Meteorology
Abstract
The Atlantic Meridional Overturning Circulation (AMOC for short) transports warm and saline Atlantic surface waters northward to high polar latitudes where it is transformed into colder (and also fresher) water, which sinks and returns southward underneath the warm waters. The Gulf stream is the best known surface current that contributes to carrying the warm surface waters to the north. The strength of this exchange flow has been monitored now for 10 years at Latitude 26N (Florida-Africa). Models suggest that low frequency changes in this AMOC flow may (i) be predictable some years ahead, and (ii) lead to changes in North Atlantic weather and climate some years later due to changing the warm water distribution at the ocean surface. To realise the potential of the AMOC monitoring measurements at 26N these observations need to be successfully "assimilated" into the ocean and climate prediction models being currently used at the Met Office and elsewhere. This project will develop novel methods to introduce the AMOC observational data into the latest ocean and climate model environments, in combination with other complementary datasets that are available, e.g. from ocean profiling floats (ARGO), and from satellites measuring sea surface temperatures and sea level. The experiments will be carried out in close collaboration with scientists from the Met Office and the European Centre for Medium Range Weather Forecasts (ECMWF) in order to allow rapid take up of successful innovations.
Planned Impact
The project will allow a key climate monitoring dataset, the Trans-Atlantic "Atlantic Meridional Overturning Circulation or AMOC" array at 26N across the N Atlantic ocean, to be used for the first time to directly constrain transports in ocean and climate models that are used operationally in seasonal and longer term climate predictions.
By addressing the upstream causes of variations in the AMOC in the way that the data are assimilated we hope to generate dynamically consistent AMOC circulations which can be realistically persistent within climate models and lead to increased predictability of changes in N Atlantic Sea surface temperatures, as indicated should be possible from climate model simulations.
The results will have an impact on the operational forecasting activities at the Met Office and at the ECMWF where the new assimilation approach for the AMOC should be easily adopted into the operational systems currently in use for initialising climate predictions.
The archiving and publication of the AMOC reanalysis results at BADC will lead to opportunities to use the results of the project for many other studies (as has been demonstrated from previous reanalysis datasets published in this way).
By addressing the upstream causes of variations in the AMOC in the way that the data are assimilated we hope to generate dynamically consistent AMOC circulations which can be realistically persistent within climate models and lead to increased predictability of changes in N Atlantic Sea surface temperatures, as indicated should be possible from climate model simulations.
The results will have an impact on the operational forecasting activities at the Met Office and at the ECMWF where the new assimilation approach for the AMOC should be easily adopted into the operational systems currently in use for initialising climate predictions.
The archiving and publication of the AMOC reanalysis results at BADC will lead to opportunities to use the results of the project for many other studies (as has been demonstrated from previous reanalysis datasets published in this way).
Publications

Haines K
(2022)
Variability and Feedbacks in the Atlantic Freshwater Budget of CMIP5 Models With Reference to Atlantic Meridional Overturning Circulation Stability
in Frontiers in Marine Science

Hermanson L
(2014)
A novel transport assimilation method for the Atlantic meridional overturning circulation at 26°N
in Quarterly Journal of the Royal Meteorological Society

Jackson L
(2019)
The Mean State and Variability of the North Atlantic Circulation: A Perspective From Ocean Reanalyses
in Journal of Geophysical Research: Oceans

Mignac D
(2019)
Decoupled Freshwater Transport and Meridional Overturning in the South Atlantic
in Geophysical Research Letters

Mignac D
(2018)
South Atlantic meridional transports from NEMO-based simulations and reanalyses
in Ocean Science

Polo I
(2020)
Can the boundary profiles at 26° N be used to extract buoyancy-forced Atlantic Meridional Overturning Circulation signals?
in Ocean Science

Stepanov V
(2014)
Mechanisms of Atlantic Meridional Overturning Circulation variability simulated by the NEMO model
in Ocean Science

Storto A
(2019)
Ocean Reanalyses: Recent Advances and Unsolved Challenges
in Frontiers in Marine Science
Description | Multiple wave signals connect the Labrador sea with the meridional heat transport throughout the N Atlantic. These have been demonstrated in ocean only and coupled models used for climate predictions. This will help Hadley centre use ocean data to initialize climate predictions. A comparison of the RAPID array data with the depth structure of signals in a model at 26N in the Met Office model show encouraging similarity suggesting that at leats on timescales <10 years that models can reproduce observed variability well, Polo et al (2020) A new data assimilation approach has been tested in idealised system and published. This method has now been implemented in the Met Office operational ocean assimilation system. A reanalysis using the RAPID array data has been successfully produced (the model is closer to observations). Impacts of this on other aspects of model prediction are currently under investigation. A new ocean reanalysis (state estimate) has been produced using the Met Office Glosea5 system. This reanalysis produces an AMOC closer to the assimilated observations and indeed reduces the amplitude of corrections coming form some other datasets. It should be a better product for further analysis and applications and is being written up for publication at the moment. |
Exploitation Route | Important for developing plans to monitor ocean circulation to initialize decadal climate forecasts. |
Sectors | Environment |
Description | A data assimilation system capable of using lagged covariance information is now available for further testing and application in the met office ocean reanalysis framework. A new met office reanalysis has been produced incorporating the new methodology discussed above and this will be available to the community through the NERC data centre at CEDA. |
Sector | Environment |
Impact Types | Societal |
Title | Ocean Reanalysis including RAPID Array Data |
Description | New Reanalysis based on Met Office Glosea5 system but including additional impact from assimilating RAPID array data |
Type Of Material | Database/Collection of data |
Year Produced | 2019 |
Provided To Others? | No |
Impact | Reanalysis data will be transferred to CEDA and published by June 2019 |
Description | NEMOVAR for Ocean Reanalysis |
Organisation | Meteorological Office UK |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | Collaboration to Port NEMOVAR code to Monsoon and then Archer allowing operational ocean assimilation code to be used by academic community |
Collaborator Contribution | Part time support over period of ~9 months for code porting and testing |
Impact | NEMOVAR now working on Monsoon and Archer |
Start Year | 2014 |
Description | NEMOVAR for Ocean Reanalysis |
Organisation | National Centre for Atmospheric Science (NCAS) |
Country | United Kingdom |
Sector | Charity/Non Profit |
PI Contribution | Collaboration to Port NEMOVAR code to Monsoon and then Archer allowing operational ocean assimilation code to be used by academic community |
Collaborator Contribution | Part time support over period of ~9 months for code porting and testing |
Impact | NEMOVAR now working on Monsoon and Archer |
Start Year | 2014 |
Description | North Atlantic Reanalysis Intercomparison |
Organisation | Meteorological Office UK |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | Development of paper for special issue on Atlantic Overturning circulation |
Collaborator Contribution | Lead author Laura Jackson Met Office. Other collaborators in Italy, France and US(MIT) |
Impact | Research paper published in special issue of JGR on AMOC Jackson et al 2019 |
Start Year | 2017 |
Description | Ocean Reanalysis Intercomparison Project |
Organisation | European Centre for Medium Range Weather Forecasting ECMWF |
Country | United Kingdom |
Sector | Public |
PI Contribution | Contributions to several papers assessing different aspects of ocean reanalyses CoChaired and co-organised internaitonal meetings on this topic Support for EU COST project bid (successful and starting 2015) (Haines now Vice-chair) |
Collaborator Contribution | Contributions to several papers assessing different aspects of ocean reanalyses |
Impact | Clivar Exchanges Issue 64. http://www.clivar.org/sites/default/files/documents/Exchanges64.pdf |
Start Year | 2009 |
Description | Ocean Reanalysis Intercomparison Project |
Organisation | Meteorological Office UK |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | Contributions to several papers assessing different aspects of ocean reanalyses CoChaired and co-organised internaitonal meetings on this topic Support for EU COST project bid (successful and starting 2015) (Haines now Vice-chair) |
Collaborator Contribution | Contributions to several papers assessing different aspects of ocean reanalyses |
Impact | Clivar Exchanges Issue 64. http://www.clivar.org/sites/default/files/documents/Exchanges64.pdf |
Start Year | 2009 |
Description | Smoother for Met Office ocean reanalyses |
Organisation | Meteorological Office UK |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | New smoother algorithm developed which allows 4D assimilation of ocean data without running adjoint and can b applied to current operational reanalysis data. |
Collaborator Contribution | Met Office prepared ocean reanalysis data saving additional information |
Impact | Dong, B., K. Haines and M. Martin. (2021) Improved high resolution ocean reanalyses using a simple smoother algorithm. JAMES, https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2021MS002626 A new ocean reanalysis product from Met Office will result after further testing |
Start Year | 2019 |
Description | CLIVAR CONCEPT-Heat Earth Energy Budget Workshop |
Form Of Engagement Activity | A formal working group, expert panel or dialogue |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Study participants or study members |
Results and Impact | This is a special focus group of CLIVAR tasked with developing improved results for quantifying the earth energy imbalance over coming few years. Haines is on steering team |
Year(s) Of Engagement Activity | 2015 |
URL | http://www.clivar.org/news/successful-concept-heat-workshop |
Description | EU COST program Evaluating Ocean Syntheses |
Form Of Engagement Activity | A formal working group, expert panel or dialogue |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Other audiences |
Results and Impact | Haines is Vice Chair of this COST project and Valdivieso is a Workpackage leader. Project is in 2nd year (runs for 4 years) running workshops and training programs as well as short term science visits, especially for early career scientists. |
Year(s) Of Engagement Activity | 2015,2016 |
URL | http://eos-cost.eu |