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A before and after shot of the rapidly retreating sea ice in the McClure Strait and Parry Channel, part of the famous "northwest passage”.

Moderate Resolution Imaging Spectroradiometer (MODIS)/NASA

The sea ice that covers the Arctic Ocean has shrunk to a record low this summer, prompting concerns that rising northern temperatures could affect Arctic communities and cause more erratic weather patterns in the south.

The U.S. National Snow and Ice Data Center reported this week that the area covered by pack ice had dipped below 4 million square kilometres for the first time in recorded history. The data centre has collected satellite images of sea ice in the Arctic since 1979, and the average summer ice coverage during the 1980s and 1990s was 6.7 million square kilometres.

"It's very likely the lowest [summer sea ice cover] in a century," said Mark Serreze, director of the NSIDC. "We are seeing the effect of a warming planet, and in particular a warming Arctic."

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It's part of a long-term trend that can be attributed to climate change, he said, adding climate models have long predicted that the Arctic would be the site of the earliest and most pronounced effects of a warming planet.

"I'm certainly surprised at how low the sea ice is, but I'm not surprised regarding the overall trend being observed," he added.

Son Nghiem, a research scientist at NASA's Jet Propulsion Laboratory, said Arctic ice is becoming thinner, weaker and younger – and therefore breaking away and melting more easily.

Ocean water is slower to adjust to seasonal changes than the atmosphere, so Arctic sea ice usually reaches its lowest level in September. That means the level of ice coverage could drop even further in the coming weeks.

Some researchers have warned that a long-term loss of summer sea ice could affect weather patterns further south, by warming the Arctic and changing the nature of the clashes between warm and cold fronts that are responsible for storms.

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