.. _ssmi_ice_area:

Ice area and extent time series: SSM/I derived
==============================================

Description
-----------
The sea ice data presented here were derived from satellite
passive-microwave radiometers, specifically, the Scanning Multichannel
Microwave Radiometer (SMMR) on NASA's Nimbus 7 satellite, for November
1978-August 1987, a sequence of Special Sensor Microwave Imagers (SSMIs)
on the F8, F11, and F13 satellites of the Defense Meteorological
Satellite Program (DMSP), for August 1987-December 2007, and the Special
Sensor Microwave Imager Sounder (SSMIS) on the DMSP F17 satellite for
January 2008-December 2012. The baseline data used were daily maps of
sea ice concentration. The maps are polar stereographic projections with
individual grid elements of approximately 25 km x 25 km; and the ice
concentration data are also archived at the National Snow and Ice Data
Center (NSIDC) at http://nsidc.org. The concentrations are calculated for
each ocean grid element and are used to derive 'sea ice extent', which is
calculated as the sum of all ocean elements having a sea ice
concentration of at least 15%, and 'sea ice area', which is calculated as
the sum over all ocean grid elements of the product of ice concentration
and grid element area. The data sets provided here include the
hemispheric totals and additionally the values for nine regions in the
Arctic and five regions in the Antarctic. These regions are identified in
Figures 1 and 2 respectively. Figures 3 and 4 provide plots of the trends
in the Arctic and Antarctic sea ice extents, along with monthly
deviations and 12-month running means. The monthly deviations are
calculated by taking the individual month's ice extent/area and
subtracting from it the average over the course of the data set of the
extents/areas for that month.

Source
------
`NASA Ice area and extent website`_

Release Policy
--------------
NASA data are not copyrighted; however, when you publish our data or
results derived therefrom, we request that you include an acknowledgment
within the text of the publication and reference list.
`Data Citation and Acknowledgements`_

References
----------
- `Cavalieri et al. (1999)`_
- `Cavalieri et al. (2012)`_
- `Cavalieri and Parkinson (2012)`_
- `Parkinson et al. (1999)`_
- `Parkinson and Cavalieri (2012)`_
- `Zwally et al. (2002)`_

`bibtex file`_

MPAS-Analysis Tasks
-------------------
- :ref:`task_timeSeriesSeaIceAreaVol`

.. _`NASA Ice area and extent website`: https://neptune.gsfc.nasa.gov/csb/index.php?section=59
.. _`Data Citation and Acknowledgements`: https://podaac.jpl.nasa.gov/CitingPODAAC
.. _`Cavalieri et al. (1999)`: https://doi.org/10.1029/1999JC900081
.. _`Cavalieri et al. (2012)`: https://doi.org/10.1109/LGRS.2011.2166754
.. _`Cavalieri and Parkinson (2012)`: https://doi.org/10.5194/tc-6-881-2012
.. _`Parkinson et al. (1999)`: https://doi.org/10.1029/1999JC900082
.. _`Parkinson and Cavalieri (2012)`: https://doi.org/10.5194/tc-6-871-2012
.. _`Zwally et al. (2002)`: https://doi.org/10.1029/2000JC000733
.. _`bibtex file`: https://web.lcrc.anl.gov/public/e3sm/diagnostics/observations/SeaIce/IceArea_timeseries/obs.bib