Data and images shown in Charctic use passive microwave data from the Defense Meteorological Satellite Program (DMSP) F17 and F18 Special Sensor Microwave Imager/Sounder (SSMIS). Data sets include the Sea Ice Index, Near-Real-time DMSP SSM/I-SSMIS Daily Polar Gridded Sea Ice Concentrations, and the NASA-produced Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I Passive Microwave Data.
The underlying data used to produce these images and graphs may be obtained from NSIDC. NSIDC produces the daily extent values using a five-day trailing mean. Graphs shown here may vary slightly from graphs displayed in Arctic Sea Ice News & Analysis, due to differences in handling leap years. However, the underlying data values are the same that NSIDC displays for its daily extent image and graph.