As previously reported, temperatures in the Arctic were as much as 14 degrees above average through parts of July, and now the National Snow and Ice Data Center has finalized its measurements of sea ice for the month. Not surprisingly, it's another record in a long list of records for Arctic melting.
In July 2011, there were 81,000 square miles of open water that would have been covered in ice in an average year. That's an area nearly the size of Kansas.
The previous record for a melt year was set in 2007, but that record was approached nearly every year since, as the trend in climate change remains very clear at the top of the world. The Arctic is responding more quickly than other parts of the Earth to global warming in part because as ice melts, sunlight that had reflected off its white surface is now absorbed by darker open water, leading to a cycle of increased warming and increased melting year after year.
The image featured here demonstrates the increased vulnerability that young sea ice faces each summer, with blue representing 15% ice cover and white 100% ice cover. Relatively thin, ice that is only one or two years old is more likely to melt than older, thicker ice. Over time, the extent of old, thick ice has declined dramatically, leaving the system increasingly vulnerable to dramatic changes.
The melt season ends in September, when the Arctic summer ends. That's when we'll know if 2011's melting will exceed 2007's overall. The longterm trend is clear, as this chart demonstrates:
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