Alek Petty (alek.a.petty[@]

The scientific questions that will be studied:
This theme will investigate snow on sea ice in CMIP6 models. As our knowledge of snow on sea ice in global climate models is a relatively new line of enquiry, we expect this theme to start with a basic intercomparison analysis. From here we hope to explore deeper questions, including:
– How sophisticated is the snow physics included in the CMIP6 models.
– Has the inclusion and sophistication of snow physics improved since CMIP5?
– Do the models that include a prognostic snow layer produce more accurate sea ice simulations?

The processes that will be investigated:
-For the models that include a prognostic snow layer, how does snow form and melt, and how is it redistributed in the different models? What is the snow mass balance?
– What are the major differences between the representation of snow on sea ice in Arctic and Antarctic simulations across the models.
-How much snow ice conversion is occurring in the models that include this process. How does this vary across the Arctic and Antarctic.
The type of analyses that will be conducted:
-The analysis will start from a pretty basic level of model intercomparison, as to our knowledge, no such assessment of snow on sea ice in GCMs has been produced to-date (likely due to the basic treatment of snow in GCMs).


•    In CMIP5, models, snowfall is increasing, so delayed freezeup is driving the declining snow depth (Hezel et al., 2012, GRL). Does this still hold in the CMIP6 models? Analysis is under way (Petty et al. in        preparation)

•    Comparison of Freeze-up versus snowfall/precipitation changes in observations is under way (Webster & Petty, in prep)