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Sea Ice ECV project



Polar sea ice is both an indicator and a driver of global climate change. We now have over 40 years of satellite data to directly monitor its evolution in concentration, area, and extent (since the late 1970s) and almost 30 years for its thickness (since the early 1990s).

In the Arctic, sea-ice extent and volume have decayed in all seasons, with strongest reduction in late summer. This leads to a younger and more mobile sea-ice cover in the Arctic Ocean. In the Southern Hemisphere, sea-ice extent increased rather steadily until 2015, with much smaller coverage since 2016. The Special Report for a 1.5C Global Warming (IPCC SR15) documents that to limit global warming to 1.5C above pre-industrial levels could “substantially” reduce the risk of sea ice-free summers in the Arctic with respect to a 2C warming.

Although satellite observations are the foundation for most of our knowledge about the evolution of the global sea-ice cover, progress is still acutely needed to improve the observations of the Sea Ice Essential Climate Variable, in particular to achieve better spatial resolution, better consistency across satellite missions, and longer time-series. These are some of our research focii in the Sea_ice_cci project.


The ultimate objective of Sea_ice_cci is to advance the retrieval capability for two main variables of the Sea Ice Essential Climate Variable (ECV): sea-ice concentration and sea-ice thickness. Our research plan was designed to approach the GCOS requirements, and maximize the impact of CCI research to operational climate information services.

For sea-ice concentration (SIC), our efforts will be towards improving the spatial resolution of the Climate Data Records, by using the high-frequency channels available on the microwave radiometry missions since 1992. Starting with SSM/I F10, we now have an almost 30 years time-series with frequencies around 90 GHz. They offer higher spatial resolution, but also lead to larger retrieval uncertainties compared to the “classic” frequency channels available since the late 1970s. We will develop innovative algorithms that will combine all frequency channels, and balance between higher spatial resolution and lower accuracy. In addition, we will attempt to retrieve sea-ice cover information from the legacy ESMR instrument on board Nimbus-5 (1972-1977). ESMR was a pioneering instrument, and dedicated algorithms must be developed. All our SIC developments are coordinated with those of the EUMETSAT Ocean and Sea Ice Satellite Application Facility (OSI SAF,

For sea-ice thickness (SIT), a main objective is to consistently extend the existing Envisat+Cryosat2 time-series (2002-present) with data from ERS-1 and ERS-2 missions (1993 onwards). This is a challenging task due to the difference in technology between ERS and Envisat (ERS recorded blurred, lower-resolution pulses wrt Envisat). Another challenge is our incomplete knowledge of the snow cover since the early 1990s. Indeed, snow plays a crucial role in observing sea-ice thickness using space-borne altimeters, both for radar penetration, and conversion from freeboard to thickness. Other general algorithm developments, such as better uncertainty characterization, and gap-filling of the large polar observation hole (north for 81N for most of the period) will be tackled. All our SIT developments are coordinated with those of the Copernicus Climate Change Service (C3S).



"Frozen Seas" pilot episode [31/05/2019]

The Sea Ice ECV is the focus of "Frozen Seas", the pilot episode of the podcast series "Views from the Void" hosted by ESA's Anna Maria Trofaier. This first episode features our own Eero Rinne! Listen to "Frozen Seas" here, and follow the podcast on Twitter.

Sea_Ice_cci at ESA LPS19 [13-17/05/2019]

The project was well represented at LPS. It was too early in the project to hold a dedicated presentation, but we had orals and posters describing our achievements in previous phases, and plans for this new project.

Sea_Ice_cci Kick-Off meeting [24-25/04/2019]

The project team gathered at the Norwegian Meteorological Institute in Oslo, Norway. We updated each others on the progress since the end of previous phase (especially the on-going validation activities), and detailed our plans for the first year of the project. Now, "au boulot!".  

About the project

The objectives described above are ambitious, and will not be addressed up-front. We rather designed a series of three 1-year development cycles to gradually develop the algorithms, and prepare better climate data records.

Each yearly phase will include the following steps: 1) update user’s requirements, 2) algorithm developments, 3) prototype software and process data, 4) scientific validation, and 5) climate assessment.

A series of deliverables (documents and datasets) will be released throughout the project. Follow this space and/or take contact.

Sea_ice_cci now enters a 3rd project phase, the first under the "CCI+" umbrella. Previous two phases involved many of the same partners, and was led by S. Sandven (NERSC, NO). 

The project team

The Consortium is based on a close collaboration between the following partners:

Resources, data and documents

Some key documents from this phase:


Some key documents from earlier phases are:

Products description

Sea Ice Concentration

Round-Robin Data Package (SIC RRDP)

SICCI-25km v2.1 (2017)

SICCI-50km v2.1 (2017)

OSI-450 (2017) and OSI-430-b (ICDR)


Sea Ice Thickness

Envisat Monthly (NH, SH), and Swath data (NH, SH) (2018)

CryoSat-2 Monthly (NH, SH), and Swath data (NH, SH) (2018)

Envisat and CryoSat-2 NH (ICDR)
Find a list of all our CCI Sea Ice products (including old/deprecated versions) in the CEDA Catalogue:



Publications presenting results and outcomes of CCI Sea Ice

Kern, S., Lavergne, T., Notz, D., Pedersen, L. T., Tonboe, R. T., Saldo, R., and Sørensen, A. M.: Satellite passive microwave sea-ice concentration data set intercomparison: closed ice and ship-based observations, The Cryosphere, 13, 3261–3307,, 2019.

Sallila, H., Farrell, S. L., McCurry, J., and Rinne, E.: Assessment of contemporary satellite sea ice thickness products for Arctic sea ice, The Cryosphere, 13, 1187-1213,, 2019.

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., and Pedersen, L. T.: Version 2 of the EUMETSAT OSI SAF and ESA CCI sea-ice concentration climate data records, The Cryosphere, 13, 49-78,, 2019.

Korosov, A. A., Rampal, P., Pedersen, L. T., Saldo, R., Ye, Y., Heygster, G., Lavergne, T., Aaboe, S., and Girard-Ardhuin, F.: A new tracking algorithm for sea ice age distribution estimation, The Cryosphere, 12, 2073-2085,, 2018.

Paul, S., Hendricks, S., Ricker, R., Kern, S., and Rinne, E.: Empirical parametrization of Envisat freeboard retrieval of Arctic and Antarctic sea ice based on CryoSat-2: progress in the ESA Climate Change Initiative, The Cryosphere, 12, 2437-2460,, 2018.

Lu, J., Heygster, G., and Spreen, G.: Atmospheric Correction of Sea Ice Concentration Retrieval for 89 GHz AMSR-E Observations, IEEE J-STARS., 11, 1442–1457,, 2018.

Kern, S., and B. Ozsoy-Cicek: Satellite remote sensing of snow depth on Antarctic sea ice: An inter-comparison of two empirical approaches, Rem. Sens., 8(6), 450, doi:10.3390/rs8060450, 2016.

Schwegmann, S., Rinne, E., Ricker, R., Hendricks, S., and Helm, V.: About the consistency between Envisat and CryoSat-2 radar freeboard retrieval over Antarctic sea ice, The Cryosphere, 10, 1415-1425,, 2016.

Kern, S., B. Ozsoy-Cicek, and A. P. Worby: Antarctic sea-ice thickness retrieval from ICESat: Inter-comparison of different approaches, Rem. Sens., 8(7), 538, doi:10.3390/rs8070538, 2016.

Kern, S., A. Rösel, L. T. Pedersen, N. Ivanova, R. Saldo, and R. T. Tonboe, The impact of melt ponds on summertime microwave brightness temperatures and sea ice concentrations, The Cryosphere, 10(5), 2217-2239, doi:10.5194/tc-10-2217-2016, 2016.

Ivanova, N., L. T. Pedersen, R. T. Tonboe, S. Kern, G. Heygster, T. Lavergne, A. Sorensen, R. Saldo, G. Dybjkaer, L. Brucker, and M. Shokr: Inter-comparison and evaluation of sea ice algorithms: towards further identification of challenges and optimal approach using passive microwave observations, The Cryosphere, 9, 1797-1817, doi:10.5194/tc-9-1797-2015, 2015.

Kern, S., and G. Spreen: Uncertainties in Antarctic sea ice thickness retrieval from ICESat, Ann Glaciol., 56(69), 107-119, doi:10.3189/201AoG69A736, 2015.

Kern, S., K. Khvorostovsky, H. Skourup, E. Rinne, Z. S. Parsakhoo, V. Djepa, P. Wadhams, and S. Sandven: The impact of snow depth, snow density, and ice density on sea ice thickness retrieval from satellite radar altimetry: Results from the ESA-CCI Sea Ice ECV Project Round Robin Exercise, The Cryosphere, 9(1), 37-52, doi:10.5194/tc-9-37-2015, 2015.

Mäkynen, M., S. Kern, A. Rösel, and L. T. Pedersen: On the Estimation of Melt Pond Fraction on the Arctic Sea Ice with ENVISAT WSM Images, Trans. Geosci. Rem. Sens., 52(11), 7366-7379, doi:10.1109/TGRS.2014.2311476, 2014.

Other related publications by our team

Quartly, G.D.; Rinne, E.; Passaro, M.; Andersen, O.B.; Dinardo, S.; Fleury, S.; Guillot, A.; Hendricks, S.; Kurekin, A.A.; Müller, F.L.; Ricker, R.; Skourup, H.; Tsamados, M. Retrieving Sea Level and Freeboard in the Arctic: A Review of Current Radar Altimetry Methodologies and Future Perspectives. Remote Sens. 2019, 11, 881.

Gerland, S., D. Barber, W. N. Meier, C. J. Mundy, M. Holland, S. Kern, Z. Li, C. Michel, D. Perovich, and T. Tamura: Essential gaps and uncertainties in the understanding of the roles and functions of Arctic sea ice, Environmental Research Letters, 14(4),, 2019.

Krumpen, T., Belter, J., Boetius, A., Damm, E., Haas, C., Hendricks, S., Nicolaus, M., Noethig, E. M., Paul, S., Peeken, I., Ricker, R. and Stein, R. (2019): Arctic warming interrupts the Transpolar Drift and affects long-range transport of sea ice and ice-rafted matter, Scientific Reports, (9). doi: 10.1038/s41598-019-41456-y

Jena, B., A. Kumar, M. Ravichandran, and S. Kern: Mechanisms of sea-ice expansion in the Indian Ocean sector of Antarctica: Insights from satellite observation and model reanalysis, PLoS ONE 13(10): e0203222, doi:10.1371/journal.pone.0203222, 2018.

Li, H., H. Xie, S. Kern, W. Wan, B. Ozsoy, S. Ackley, and Y. Hong: Spatio-temporal variability of Antarctic sea-ice thickness and volume obtained from ICESat data using an innovative algorithm, Remote Sensing of Environment, 219, 44-61, doi:10.1016/j.rse.2018.09.031, 2018.

Contact us / support

Use the following emails to contact the Sea_ice_cci team:

  • Scientific leader: thomas.lavergne[at]
  • ESA technical officer: Anna.Maria.Trofaier[at]