Mohrmann et al. (2021) Southern Ocean polynyas in CMIP6 models

M. Mohrmann, C. Heuzé, and S. Swart (2021) Southern Ocean polynyas in CMIP6 models, The Cryosphere, vol 15, pp. 4281–4313, doi:10.5194/tc-15-4281-2021.

We use daily and monthly sea ice concentration and sea ice thickness output from 27 models that participated in the Climate Model Intercomparison Project phase 6 (CMIP6) to evaluate their representation of polynyas, i.e. openings in the winter sea ice, in the Southern Ocean. We find that:

  • The daily sea ice thickness output has serious issues;
  • Few models have very large open ocean polynyas, but open ocean polynyas feature in most models too often;
  • The majority of models overestimate the area of coastal polynyas;
  • For most models, the polynya occurrence and area is larger if using daily output instead of monthly, or if using sea ice thickness instead of concentration;
  • Too few model families provided CM and ESM versions for us to be certain, but CM versions seem to have a better representation of coastal polynyas, likely because they can be run at higher resolution;
  • The Southern Annular Mode and open ocean polynya activity are surprisingly not correlated in the models. Instead, we find a relationship with the Antarctic Circumpolar Current (ACC): the models with the largest open ocean polynya are the ones with the most realistic ACC, although it is unclear which process causes the other one.
Fig. 4 from Mohrmann et al. (2021) showing the agreement between observations (left) and the highest resolution model (right, 25 km)

Download the full text here.

One thought on “Mohrmann et al. (2021) Southern Ocean polynyas in CMIP6 models

  1. Pingback: Research theme: Antarctic polynyas | Dr Céline Heuzé

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