The mixed-layer depth in the Ocean Model Intercomparison Project (OMIP): impact of resolving mesoscale eddies

Details

• Journal Title:
  Geoscientific Model Development
• Personal Author:
  Treguier, Anne Marie ; de Boyer Montégut, Clement ; Bozec, Alexandra ; Chassignet, Eric P. ; Fox-Kemper, Baylor ; McC. Hogg, Andy ; Iovino, Doroteaciro ; Kiss, Andrew E. ; Le Sommer, Julien ; Li, Yiwen ; Lin, Pengfei ; Lique, Camille ; Liu, Hailong ; Serazin, Guillaume ; Sidorenko, Dmitry ; Wang, Qiang ; Xu, Xiaobio ; Yeager, Steve
• NOAA Program & Office:
  OAR (Oceanic and Atmospheric Research)
• Description:
  The ocean mixed layer is the interface between the ocean interior and the atmosphere or sea ice and plays a key role in climate variability. It is thus critical that numerical models used in climate studies are capable of a good representation of the mixed layer, especially its depth. Here we evaluate the mixed-layer depth (MLD) in six pairs of non-eddying (1∘ grid spacing) and eddy-rich (up to 1/16∘) models from the Ocean Model Intercomparison Project (OMIP), forced by a common atmospheric state. For model evaluation, we use an updated MLD dataset computed from observations using the OMIP protocol (a constant density threshold). In winter, low-resolution models exhibit large biases in the deep-water formation regions. These biases are reduced in eddy-rich models but not uniformly across models and regions. The improvement is most noticeable in the mode-water formation regions of the Northern Hemisphere. Results in the Southern Ocean are more contrasted, with biases of either sign remaining at high resolution. In eddy-rich models, mesoscale eddies control the spatial variability in MLD in winter. Contrary to a hypothesis that the deepening of the mixed layer in anticyclones would make the MLD larger globally, eddy-rich models tend to have a shallower mixed layer at most latitudes than coarser models do. In addition, our study highlights the sensitivity of the MLD computation to the choice of a reference level and the spatio-temporal sampling, which motivates new recommendations for MLD computation in future model intercomparison projects.
• Keywords:
  General Medicine
• Source:
  Geoscientific Model Development, 16(13), 3849-3872
• DOI:
  https://doi.org/10.5194/gmd-16-3849-2023
• ISSN:
  1991-9603
• Format:
  PDF
• Publisher:
  Copernicus GmbH
• Document Type:
  Journal Article
• Funding:
  Grant no. NA19OAR4310366
• License:
  https://creativecommons.org/licenses/by/4.0/
• Rights Information:
  CC BY
• Compliance:
  Library
• Main Document Checksum:
  urn:sha256:e848dc3a64269a2b207c0c39f623137d8d70213d9923bff37d46fc313429c67f
• Download URL:
  https://repository.library.noaa.gov/view/noaa/58396/noaa_58396_DS1.pdf
• File Type:
  [PDF - 9.73 MB ]