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.
00:04Arctic sea ice naturally grows in the winter, peaks around March, and melts in the summer, lowest around September.
00:12But on long timescales, both winter and summer ice extents are declining.
00:182. Long-term Decline
00:19Satellites have tracked sea ice since 1978.
00:24There's a strong downward trend in summer, September, minimum extent, especially since the early 2000s.
00:31Winter, March, recoveries are also weaker, there's less multi-year ice, ice that survives more than one melt season, and more first-year ice.
00:413. Causes of Ice Loss
00:42While natural variability, like the Arctic Oscillation, plays a role, the sharp decline in Arctic sea ice cannot be explained by natural variability alone.
00:52Rising global temperatures are a big factor, warming has increased melt, and the ice isn't recovering as much in winter.
01:00Some climate models predict that parts of the Arctic could become ice-free in summer before the end of the 21st century.
01:085. How Data is Collected
01:10The time series is based on measurements from microwave sensors on satellites, e.g. Nimbus 7, NOAA satellites.
01:18Satellites detect differences in microwave emissions between ice and open water, which helps map sea ice concentration.
01:25There is a pole hole, a region near the North Pole, where satellite sensors historically couldn't collect data.
01:32Data models assume that area is ice-filled.
01:356. Visualization
01:37The page shows image pairs for September, minimum, and March, maximum, from 1990 to 2025.
01:45There's a yellow outline in the images representing the 1981 to 2010 median for sea ice extent, useful as a baseline to compare changes.
01:53Why it matters
01:55Climate indicator
01:57The decline in Arctic sea ice is one of the clearest indicators of global warming.
02:03Feedback effects
02:04Less ice means more dark ocean water exposed, which absorbs more heat, albedo effect, accelerating warming.
02:12Ecosystems at risk
02:13Many Arctic species depend on sea ice, polar bears, seals, etc., so losing ice endangers their habitat.
02:20Global impact
02:22Melting ice contributes to sea level rise and can change ocean circulation patterns, potentially affecting weather globally.
02:30Human activity
02:31As ice becomes thinner and less extensive, Arctic shipping and resource extraction could increase, but this comes with geopolitical, environmental, and safety risks.
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