Page Overview & Data Sources

• This page provides time series and map visualizations for daily polar sea ice extent and concentration from satellite-based data products. Ice extent estimates shown in the chart are from the Sea Ice Index (version 4) dataset developed by the National Snow and Ice Data Center (NSIDC). Each value is a 5-day mean of the total area where ice concentration is 15% or greater. An interactive chart is also available from the NSIDC here.


• Update August 5, 2025: This chart now uses Sea Ice Index version 4, which has small differences from version 3 for sea ice extents in 2025. Version comparisons are shown here.


• The sea ice concentration maps are generated from 0.5°x0.5° analysis fields from the NCEP Climate Forecast System (1979-2022) and NCEP Global Data Assimilation System (2023-present). See a map for a different date by clicking a data point on the time series chart. Switch views between Northern and Southern Hemisphere by clicking on the toggle button below the chart. The maps can be animated on the Daily Temperature, SST, and Sea Ice page.


• The chart and maps update daily with a one-day lag from observations depending on availability of the source data products.


• NCAR Command Language is used for data processing and map generation. The interactive time series chart is made using HighCharts.

Last updated 5 August 2025