Key Points from the Page
1. Seasonal Fluctuations
Arctic sea ice grows in winter (peaks around March) and melts a lot in summer (minimum around September).
This is a natural cycle, but recent decades show a change in the trend.
2. Long-Term Decline
Since 1978, satellite observations have shown a clear overall decline in Arctic sea ice.
The decline has gotten steeper in the 21st century.
Since about 2002, the minimum summer ice (in September) has not returned to the long-term average.
3. Change in Ice Types
There’s much less multiyear ice (ice that survives multiple years) and more annual ice.
Multiyear ice is more stable and thick; losing that makes the sea ice more vulnerable.
4. Causes
While natural variability (like the Arctic Oscillation) affects ice extent, the sharp long-term decline cannot be explained by natural cycles alone.
Rising global temperatures are a key driver.
Some climate models predict that parts of the Arctic could become seasonally ice-free before the end of this century.
5. How Data Is Collected
The time series is based on measurements from microwave sensors on satellites (e.g., Nimbus-7, NOAA satellites).
Satellites detect differences in microwave emissions between ice and open water, which helps map sea ice concentration.
There is a “pole hole” (a region near the North Pole) where satellite sensors historically couldn’t collect data; data models assume that area is ice-filled.
6. Visualization
The page shows image pairs for September (minimum) and March (maximum) from 1990 to 2025.
There’s a yellow outline in the images representing the 1981–2010 median for sea ice extent—useful as a baseline to compare changes.
