Sea ice extent

Description

The sea ice extent (SIE) is defined as the areal integral of all ocean grid cells that contain at least 15% of sea ice concentration (SIC). This threshold-based definition has its drawbacks (it is subjective, it is not as physical as sea ice area, it is not linear under time averaging) but has the advantage to be practical, as it corresponds to the surface enclosed by the sea ice edge.

Further details on the definition can be gound on the National Snow and Ice Data Center (NSIDC) website.

As an index resulting from a spatial integral, the same SIE can be obtained from different SIC distributions. Therefore, for model evaluation, it is generally recommended to compute SIE over specific regions to exclude the possibility of error compensations.

Structure

The sea ice extent diagnostic follows a class structure and consists of the files:

  • seaice_class.py: a python file in which the SeaIceExtent class constructor and the other class methods are included;

  • regions.yml: a yaml file with the definitions of regions where SIE can be calculated

  • notebooks/seaice.ipynb: an ipython notebook which uses the seaice_class class and its methods;

  • README.md: a readme file which contains some technical information on how to install the sea ice diagnostic and its environment.

Input variables

  • ci (sea ice concentration, GRIB paramid 31)

  • usual model-specific invariants (latitude, longitude, grid cell areas)

Output

The script produces figSIE.pdf and figSIE.png, two figures showing the full seasonal cycles of sea ice extent in the specified regions for the available time of integrations.

The script also produces as many NetCDF files as there were items provided in the mySetups list. Each NetCDF file has the time series of sea ice extent recorded for the various regions.

Methods used

Examples from the seaIce class contained in the seaice_class.py file:

  • computeExtent: method to retrieve the data and compute the sea ice extent of the retrieved data.

  • plotExtent: method to plot the sea ice extent time series.

  • createNetCDF: method to create a NetCDF file with the sea ice extent time series.

Observations

OSI-SAF osi-450. See Lavergne et al. (2019)

References

  • Lavergne, T., Sørensen, A. M., Kern, S., Tonboe, R., Notz, D., Aaboe, S., Bell, L., Dybkjær, G., Eastwood, S., Gabarro, C., Heygster, G., Killie, M. A., Brandt Kreiner, M., Lavelle, J., Saldo, R., Sandven, S., & Pedersen, L. T. (2019). Version 2 of the EUMETSAT OSI SAF and ESA CCI sea-ice concentration climate data records. The Cryosphere, 13(1), 49–78. https://doi.org/10.5194/tc-13-49-2019

Example Plot(s)

../_images/figSIE.png

Available demo notebooks

Notebooks are stored in diagnostics/seaice/notebooks

Detailed API

This section provides a detailed reference for the Application Programming Interface (API) of the “seaice” diagnostic, produced from the diagnostic function docstrings.

class seaice.SeaIceConcentration(config, loglevel: str = 'WARNING', outputdir=None)

Bases: object

The SeaIceConcentration constructor.

Parameters:

  • config (str or dict) – If str, the path to the yaml file containing the configuration. If dict, the configuration itself.

  • loglevel (str) – The log level Default: WARNING

Returns:

A SeaIceConcentration object.

configure(config=None)

Sets the list of setups

plotConcentration()
run()

The run diagnostic method.

The method produces as output a figure with the winter and summer spatial distributions of sea ice concentration averaged in time (Arctic and Antarctic)

class seaice.SeaIceExtent(config, loglevel: str = 'WARNING', threshold=0.15, regions_definition_file=None, outputdir=None)

Bases: object

Sea ice extent class

The SeaIceExtent constructor.

Parameters:

  • config (str or dict) – If str, the path to the yaml file containing the configuration. If dict, the configuration itself.

  • loglevel (str) – The log level Default: WARNING

  • threshold (float) – The sea ice extent threshold Default: 0.15

  • regions_definition_file (str) – The path to the file that specifies the regions boundaries

Returns:

A SeaIceExtent object.

computeExtent()

Method which computes the seaice extent.

configure(config=None)

Set the number of regions and the list of regions. Set also the list of setups.

createNetCDF()

Method to create NetCDF files.

plotExtent()

Method to produce figures plotting seaice extent.

run()

The run diagnostic method.

The method produces as output a figure with the seasonal cycles of sea ice extent in the regions for the setups and a netcdf file containing the time series of sea ice extent in the regions for each setup.

class seaice.SeaIceThickness(config, loglevel: str = 'WARNING', outputdir=None)

Bases: object

The SeaIceThickness constructor.

Parameters:

  • config (str or dict) – If str, the path to the yaml file containing the configuration. If dict, the configuration itself.

  • loglevel (str) – The log level Default: WARNING

Returns:

A SeaIceThickness object.

configure(config=None)

Sets the list of setups

plotThickness()

Generates thickness plots for sea ice for different models, hemispheres, and months.

run()

The run diagnostic method.

The method produces as output a figure with the winter and summer spatial distributions of sea ice thickness averaged in time (Arctic and Antarctic)

class seaice.SeaIceVolume(config, loglevel: str = 'WARNING', regions_definition_file=None, outputdir=None)

Bases: object

Sea ice volume class

The SeaIceVolume constructor.

Parameters:

  • config (str or dict) – If str, the path to the yaml file containing the configuration. If dict, the configuration itself.

  • loglevel (str) – The log level Default: WARNING

  • regions_definition_file (str) – The path to the file that specifies the regions boundaries

Returns:

A SeaIceVolume object.

computeVolume()

Method which computes the seaice Volume.

configure(config=None)

Set the number of regions and the list of regions. Set also the list of setups.

createNetCDF()

Method to create NetCDF files.

plotVolume()

Method to produce figures plotting seaice volume.

run()

The run diagnostic method.

The method produces as output a figure with the seasonal cycles of sea ice volume in the regions for the setups and a netcdf file containing the time series of sea ice volume in the regions for each setup.