EcoAlert: Dramatic Arctic Sea-Ice Melt over a Two-Week Period




These images, captured two weeks apart by NASA's Terra satellite on 17 July (below) and 3 August (above), show a stark melting of sea ice in the Arctic's North-West Passage. The region's ice cover is now significantly lower than expected, says the Canadian Ice Service, with coverage on July 30th estimated at 33 per cent, compared to the 1981-2010 median of 79 per cent. The ice retreat will continue through September, when annual ice cover is at its lowest.

These images, acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite, show significant changes over two weeks. The top image shows Parry Channel on July 17, 2012, when ice filled the channel. The bottom image shows the same region on August 3, when some ice was still clinging to the shores of Victoria and Melville Islands but open water otherwise dominated the region.

The Canadian Ice Service reported that ice cover in Parry Channel began to fall below the 1981–2010 median after July 16, 2012, and the loss accelerated over the following two weeks. On July 23, the percentage of ice cover in the channel was roughly 67 percent, compared to the median of 80 percent. On July 30, ice cover was roughly 33 percent, compared a median of 79 percent.

These photo-like images show widespread open water in early August, though patches of ice linger south of Melville Island. Walt Meier of the National Snow and Ice Data Center cautioned, however, that while the Parry Channel appeared almost entirely free of ice, it was not necessarily open for navigational purposes. Sea ice can be thin enough to avoid detection by satellite sensors such as MODIS yet still thick enough to impede ships.

Recent studies have suggested that certain organisms have begun to take advantage of the open water. The Northwest Passage opened in 2007, a year when there was record-low sea ice in the Arctic. A 2007 study on Neodenticula seminae—a type of plankton historically found in the Pacific Ocean—concluded that the species had turned up in the North Atlantic. The research suggested that the plankton’s route included the Canadian Arctic Archipelago. A 2012 study on bowhead whales, which tracked individuals with satellite transmitters, indicated that Pacific and Atlantic populations had begun to overlap in the Northwest Passage in August 2010.

The increasing temperatures and diminishing sea ice have been linked to changes in the behavior of salmon and bears. Extreme Arctic melts can leave shorelines vulnerable to erosion, and may even be responsible for the colder winters experienced in Northern Europe and North America of late.

Attempts to identify a shortcut between Europe and Asia across the Arctic date back to the late fifteenth century, just several years after Columbus journeyed to the Americas. For centuries, attempts to find the route were stymied by unfamiliar geography and unforgiving ice. The Northwest Passage was first successfully navigated by the Norwegian explorer Roald Amundsen between 1903 and 1906. He used the southern route through the Northwest Passage; Parry Channel is part of the northern or “preferred” route.




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