We released a new dataset version 300 of the SMOS/SMAP thin sea ice thickness data in our data browser. SMAP data is currently not available (since 6th of August 2022) so that our NRT product only includes SMOS data.

 

Changes compared to the previous version 205 are

• updated projection information for better GIS compatibility
• fixed slight grid shift to match official NSIDC north polar stereo grid coordinates
• fixed issue with missing SMAP data in products after September 2021
• updated to latest released SMAP L1B data (17000 to 18290)

 

update (8th Nov 2022): SMAP data is available from 5th of October 2022 again and included in our v300 product.

Thickness of thin sea ice

The thickness of thin sea ice (SIT) is daily retrieved from observations of the L-band microwave sensor SMOS (Soil Moisture and Ocean Salinity). Horizontal and vertical polarized brightness temperatures in the incidence angle range of 40° to 50° are averaged. The ice thickness is then inferred from the polarization difference and the intensity using an empirical method (Huntemann et al., 2014).

Thin sea ice occurs during the freezing season. In the melting season, the thickness of sea ice is highly variable and the emission properties in the microwave change due to the wetness of the surface and occurrence of melt ponds in the Arctic. Therefore, thickness data are calculated only during the freezing season, that is from October to April in the Arctic and from March to September in the Antarctic. During the melting season, the procedure does not yield meaningful results.

Two variants of the data SMOS sea ice thickness data are processed, an RFI filtered version and a raw unfiltered version. Despite L-band emission at the SMOS&SMAP frequency being banned for communication, strong emissions from various sources on the ground may affect the sensitive instruments and cause large errors in the ice thickness data. We use the RFI related flags in the SMOS L1C and SMAP L1b data to filter out affected data. It is, in general, advisable to use the filtered version of the SMOS product or the SMOS&SMAP combined product, where this data is filtered by default.

As the resolution of SMOS at the used incidence angle range is about 40 km, only larger regions of thin ice will be retrieved correctly. The rim of thin ice shown in many cases not necessarily indicates thin ice, but can also be caused by the smearing effect (convolution) of the low resolution.

Each day of ice thickness data product are calculated twice to ensure that all swath files were available in the archived product. First processing is done directly on the next day with only about 7 hours delay. At this time it can happen that not all swath files are available and another processing of the same day is initiated 23 hours later. In more than 50% of the time the first processing does not include all swath but usually provides sufficient coverage for Arctic and Antarctic regions.

This service has been developed in the framework of the EU project SIDARUS. After completion of the SIDARUS project end 2013, the service is continued on a best effort base in the context of the Polar View and of the Arctic Regional Ocean Observing System (Arctic ROOS).

 

Data Archive

All data can be found in the Data Archive. To quickly browse the dataset, please have a look at the Data Browser.

How to cite

Please help maintaining this service by properly citing and acknowledging if you use the data for publications:

Huntemann, M., Heygster, G., Kaleschke, L., Krumpen, T., Mäkynen, M., and Drusch, M.: Empirical sea ice thickness retrieval during the freeze-up period from SMOS high incident angle observations, The Cryosphere, 8, 439-451, doi:10.5194/tc-8-439-2014, 2014.

Contact

For questions regarding the data please contact Gunnar Spreen, Marcus Huntemann, or Georg Heygster.
For questions related to the website and data-browser please contact Malte Gerken.

Institute of Environmental Physics, University of Bremen, Germany.

The procedure and validation efforts are described in Huntemann et al. (2014) However, no warranty is given for the data presented on these pages.

Thin Sea Ice Thickness (SIT) is retrieved daily using observations from the L-band sensors SMOS (Soil Moisture and Ocean Salinity) from ESA and SMAP (Soil Moisture Active Passive) from NASA. SMOS brightness temperatures are recorded at 40 degree incidence angle using a fit function, while the incidence angle of SMAP is fixed at the same value. The mixed brightness temperature (Patilea et al., 2019) data from the two sensors is then used in the retrieval itself. The sea ice thickness is computed from the empirical correlation between SIT and two brightness temperatures parameters polarization difference and intensity (Huntemann et al., 2014). 

Thin sea appears mainly during the two freeze-up periods at the poles, October to April in the Arctic and March to September in the Antarctic. During the polar summers due to melting or other morphological changes of the sea ice surface that change the emisivity, the retrieved sea ice thickness will not be considered meaningful.

The resolution of both satellites is approximately 40~km, so just retrievals over this area or larger, should be considered to be correct. Due to the large resolution, the thin sea ice at the ice edge should be considered with care due to smearing effects. The same problem appears in coastal areas where the ocean pixels will be contaminated by land emissions, generating SIT all along the coasts.

 

The processing of the previous day data is started with a delay of 8 hours and reprocessed 24 hours later once

and again a week later. This is done to correct days when not all swaths or data is available at the time

of the first processing.

 

Data Archive

All data can be found in the Data Archive. To quickly browse the dataset, please have a look at the Data Browser.

How to cite

Please help maintaining this service by properly citing and acknowledging if you use the data for publications:

Patilea C, Heygster G, Huntemann M, Spreen G. Combined SMAP/SMOS Thin Sea Ice Thickness Retrieval.
Cryosph Discuss. 2017;25(October):1-16. doi:10.5194/tc-2017-168.

Contact

For questions regarding the data please contact Gunnar Spreen or Marcus Huntemann.

For questions related to the website and data-browser please contact Malte Gerken.

Institute of Environmental Physics, University of Bremen, Germany.

The procedure and validation efforts are described in Patilea et al (2019). However, no warranty is given for the data presented on these pages.