The sea ice diagnostics include:
- time series of Arctic and Antarctic sea ice area and extent (calculated as the total area (km2) of grid cells with sea ice concentrations (sic) of at least 15%).
- ice extent trend distributions for the Arctic in September and the Antarctic in February.
- calculation of year of near disappearance of Arctic sea ice
- scatter plots of (a) historical trend in September Arctic sea ice extent (SSIE) vs historical long-term mean SSIE; (b) historical SSIE mean vs 1st year of disappearance (YOD) RCP8.5; (c) historical SSIE trend vs YOD RCP8.5.
Recipes are stored in recipes/
- recipe_seaice.yml
Diagnostics are stored in diag_scripts/seaice/
- seaice_aux.ncl: contains functions for calculating sea ice area or extent from sea ice concentration and first year of disappearance
- seaice_ecs.ncl: scatter plots of mean/trend of historical September Arctic sea ice extent vs 1st year of disappearance (RCP8.5) (similar to IPCC AR5 Chapter 12, Fig. 12.31a)
- seaice_trends.ncl: calculates ice extent trend distributions (similar to IPCC AR5 Chapter 9, Fig. 9.24c/d)
- seaice_tsline.ncl: creates a time series line plots of total sea ice area and extent (accumulated) for northern and southern hemispheres with optional multi-model mean and standard deviation. One value is used per model per year, either annual mean or the mean value of a selected month (similar to IPCC AR5 Chapter 9, Fig. 9.24a/b)
- seaice_yod.ncl: calculation of year of near disappearance of Arctic sea ice
Script seaice_ecs.ncl
Required settings (scripts)
- hist_exp: name of historical experiment (string)
- month: selected month (1, 2, ..., 12) or annual mean ("A")
- rcp_exp: name of RCP experiment (string)
- region: region to be analyzed ( "Arctic" or "Antarctic")
Optional settings (scripts)
- fill_pole_hole: fill observational hole at North pole (default: False)
- styleset: color style (e.g. "CMIP5")
Optional settings (variables)
- reference_dataset: reference dataset
Script seaice_trends.ncl
Required settings (scripts)
- month: selected month (1, 2, ..., 12) or annual mean ("A")
- region: region to be analyzed ( "Arctic" or "Antarctic")
Optional settings (scripts)
- fill_pole_hole: fill observational hole at North pole, Default: False
Optional settings (variables)
- ref_model: array of references plotted as vertical lines
Script seaice_tsline.ncl
Required settings (scripts)
- region: Arctic, Antarctic
- month: annual mean (A), or month number (3 = March, for Antarctic; 9 = September for Arctic)
Optional settings (scripts)
- styleset: for plot_type cycle only (cmip5, cmip6, default)
- multi_model_mean: plot multi-model mean and standard deviation (default: False)
- EMs_in_lg: create a legend label for individual ensemble members (default: False)
- fill_pole_hole: fill polar hole (typically in satellite data) with sic = 1 (default: False)
Script seaice_yod.ncl
Required settings (scripts)
- month: selected month (1, 2, ..., 12) or annual mean ("A")
- region: region to be analyzed ( "Arctic" or "Antarctic")
Optional settings (scripts)
- fill_pole_hole: fill observational hole at North pole, Default: False
- wgt_file: netCDF containing pre-determined model weights
Optional settings (variables)
- ref_model: array of references plotted as vertical lines
- sic (ocean-ice, monthly mean, longitude latitude time)
- areacello (fx, longitude latitude)
Note: (1) obs4mips data can be used directly without any preprocessing; (2) see headers of cmorization scripts (in esmvaltool/utils/cmorizers/obs) for non-obs4mips data for download instructions.
- HadISST (sic - esmvaltool/utils/cmorizers/obs/cmorize_obs_HadISST.ncl)
- Massonnet, F. et al., The Cryosphere, 6, 1383-1394, doi: 10.5194/tc-6-1383-2012, 2012.
- Stroeve, J. et al., Geophys. Res. Lett., 34, L09501, doi:10.1029/2007GL029703, 2007.