-Contributed by Dirk Notz

simip seaice2The Sea-Ice Model Intercomparison Project (SIMIP) of the 6th version of the Coupled Model Intercomparison Project (CMIP6) aims at a better understanding of the role of sea ice for the Earth’s climate system. In particular, we want establish the sensitivity of sea ice to changes in the external forcing, understand differences between individual model simluations, and examine how predictable the future evolution of sea ice is on time scales ranging from days to centuries.

To reach these aims, SIMIP has compiled a new protocol for the output of sea-ice related variables from coupled model simulations. This protocol allows any researcher to analyse the three main budgets that govern the evolution of sea ice, namely conservation of heat, the momentum budget, and salt/tracer conservation. Based on an analysis of these budgets, one can identify the main reason for a different response of sea ice both within a set of models and between individual models and reality. Thus, it becomes possible to understand model biases and to improve our simulations of future sea-ice evolution. In particular, we will be able to quantify how much of the current spread of model simulations of future Arctic sea-ice evolution can possibly still be improved by improving the model, versus how much of this spread is an inherent uncertainty of the dynamic climate system controlled by internal variability.

Supported by CliC, the SIMIP Steering Committee has over the past few months had an open consulting process with sea-ice researchers from various backgrounds to settle on a protocol that forms the best possible compromise between the complete coverage of sea-ice related model output and minimizing storage requirements. This protocol is now finalised and currently under consideration by the CMIP6 panel. In particular, the panel will establish how much of this protocol will be included into the recommended set of variables that must be stored for the CMIP6 DECK experiments. Once this is done, we will eagerly await the first results from CMIP6 to start analysing sea-ice evolution in the simulations at a more detailed level than has ever been possible before.

The SIMIP protocol is available for download and further comments at: http://www.climate-cryosphere.org/activities/targeted/simip