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Mixed layer heterogeneity


The future climate of our planet depends on the way heat and carbon dioxide are absorbed by the ocean. The top 50-200 from wind, waves and convective circulations. This mixed layer mediates the transfers between the atmosphere and the deep ocean.




  • Ongoing


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Mar 2020 - Mar 2023

Type of action

Joint Call

Mixed layer heterogeneity

The future climate of our planet depends on the way heat and carbon dioxide are absorbed by the ocean. The top 50-200 metres, the ocean's surface layer, is well mixed by turbulence from wind, waves and convective circulations. This mixed layer mediates the transfers between the atmosphere and the deep ocean.

Transfers of heat, energy and gases through the mixed layer are extremely complex and spatially heterogeneous. The discontinuous and dynamic sea ice cover, and the occurrence of eddies, front and filaments at the kilometre-scale, are important heterogeneities which regulate the thickness and properties of the mixed layer. Large discrepancies in mixed layer depths are found among climate models used for IPCC scenarios, partly due to a misrepresentation of the integrated effect of these heterogeneities. This limits the usefulness of climate models in assessing the impacts of future climate change on European climate and marine ecosystems. 

MEDLEY (MixED Layer hEterogeneitY) will further our understanding of mixed layer heterogeneity in the North Atlantic a hotspot of anthropogenic CO2 storage, and in the rapidly warming Arctic Ocean.

The core objectives of MEDLEY are:

  • to evaluate the spatial heterogeneity of fluxes and of the processes controlling the ocean mixed layer
  • to improve the representation of the transfers through the mixed layer in climate models by taking this heterogeneity into account

The project integrates state of the art observational datasets and basin scale ocean models resolving the kilometre scale, an innovative sea-ice model, and the latest generation of climate models with an eddying ocean component. Building on interdisciplinary  collaborations between its members, MEDLEY will take advantage of the most recent data analysis methods (e.g., machine learning-based classification).

The MEDLEY consortium is well connected to European climate infrastructures such as the Infrastructure for the European Network for Earth System Modelling (IS-ENES) and to the Nucleus for European Modelling of the Ocean (NEMO) European ocean-ice modelling platform, thus ensuring that MEDLEY findings are built into European climate models. MEDLEY aims at a better tuning and consistency of mixed layer representation (parameterizations) in NEMO, gained through multi-scale modelling and validation by recent high-resolution observations. MEDLEY will further create new diagnostics for model evaluation to ensure that the mixed layer transfer function is better constrained in future climate models that inform the next IPCC assessments and further constrain the scientific basis for the Paris Agreement.

Project Coordinator

Coordinator: Dr. Anne Marie Tréguier

Laboratoire d'Océanographie Physique et Spatiale, CNRS, France


Laboratoire d'Océanographie Physique et Spatiale, LOPS - CNRS, FRANCE

Institut des Géosciences de l'Environnement, IGE, FRANCE

Université Catholique de Louvain la Neuve, UCLouvain, BELGIUM

Fondazione Centro Euro-Mediterraneo sui Cambiamenti Climatici, CMCC, ITALY

Nansen Environmental and Remote Sensing Cente, NERSC, NORWAY

Institute of Oceanology of the Russian Academy of Sciences, IORAS, RUSSIA