Extension des glace de mer de 1979 - 2009
NSIDC: Sea Ice Extent

September 1979-2008

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Avg. Extent

September Sea Ice Extent
Arctic Sea Ice Minimum
September 1979-2008
Sea ice extent is a measurement of the area of ocean where there is at least some sea ice. Usually, scientists define a threshold of minimum concentration to mark where the ice ends; the most common cutoff is at 15 percent. Scientists use the 15 percent cutoff because it provides the most consistent agreement between satellite and ground observations. Scientists tend to focus on Arctic sea ice extent more closely than other aspects of sea ice because satellites measure extent more accurately than they do other measurements, such as thickness.
The Arctic sea ice minimum marks the day, each year, when the sea ice extent is at its lowest. The sea ice minimum occurs at the end of the summer melting season. The summer melt season usually begins in March and ends sometime during September. The average sea ice extent for September of each year, starting with 1979, is shown. Three of the last seven years (2002, 2005 and 2007) have seen record minimums in Arctic sea ice extent.
The Arctic sea ice minimum is coincident with the Antarctic sea ice maximum.
Use the timeline tool to view the sea ice time series animation. We recommend unselecting all other time series data while viewing this time series. For help using the timeline tool see Virtual Globes: Google Earth Timelines.
See Also:
Frequently Asked Questions
State of the Cryosphere
Cryosphere Glossary
All About Sea Ice
Sea Ice Index

Data

Date

March Sea Ice Extent
Arctic Sea Ice Maximum
Sea ice extent is a measurement of the area of ocean where there is at least some sea ice. Usually, scientists define a threshold of minimum concentration to mark where the ice ends; the most common cutoff is at 15 percent. Scientists use the 15 percent cutoff because it provides the most consistent agreement between satellite and ground observations. Scientists tend to focus on Arctic sea ice extent more closely than other aspects of sea ice because satellites measure extent more accurately than they do other measurements, such as thickness.
The Arctic sea ice maximum marks the day of the year when the sea ice covers the largest area of the Arctic. The sea ice maximum occurs at the end of the winter cold season. The winter cold season usually begins in September and ends in March. Monitoring winter sea ice is also important to understanding the state of the sea ice. Scientists have found that Arctic sea ice has been recovering less in the winter, meaning the sea ice is already "weak" when the summer melting season arrives. A possible cause is that the underlying ocean is warmer.
The Arctic sea ice maximum is coincident with the Antarctic sea ice minimum.
Use the timeline tool to view the sea ice time series animation. We recommend unselecting all other time series data while viewing this time series. For help using the timeline tool see Virtual Globes: Google Earth Timelines.
See Also:
Frequently Asked Questions
State of the Cryosphere
Cryosphere Glossary
All About Sea Ice
Sea Ice Index

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