The area of ocean covered by ice shrank to 1.9 million square miles on average for the five days through Wednesday, according to the latest data from the U.S. National Snow and Ice Data Center in Boulder, Colo. With as many as five weeks of the annual melt season left, it's already the fourth-lowest annual minimum ever measured.
"Unless the melting really, really slows down, there's a very real chance of a record," said Walt Meier, a research scientist at the NSIDC. "In the last week or so it's dropped precipitously. There's definitely a chance it'll dip below (1.5 million square miles."
The shrinkage is the most visible sign of global warming according to Meier, and raises the prospect that the Arctic Ocean may become largely ice free in the summer. That opens up new shipping routes and is sparking a race for resources that's led to Cairn Energy Plc and Royal Dutch Shell Plc exploring waters off Greenland for oil and gas.
"There's a whole new frontline from a strategic standpoint," said Cleo Paskal, a geopolitical analyst at Chatham House, a policy adviser in London. "Countries that have been kept apart by a wall of ice are now facing each other for the first time and countries like China are slipping up through the middle."
China has an icebreaker, Arctic research stations, and is positioning to develop infrastructure in Greenland and tap the island's mineral wealth, Paskal said.
Cairn drilled eight wells in two years through the end of 2011 in an unsuccessful attempt to find recoverable oil and gas reserves off Greenland. Shell, Exxon Mobil, Chevron and Statoil ASA also hold licenses to drill off the Greenland coast.
The sea ice melts every summer before freezing again in September. The NSIDC uses a five-day average ice extent to iron out day-to-day anomalies. When more dark ocean is exposed, it absorbs more of the sun's heat unlike the reflective ice, increasing the warming effect in a so-called feedback loop.
The increasing melt may be a harbinger of greater changes such as the release of methane compounds from frozen soils that could exacerbate warming, and a thaw of the Greenland ice sheet, which would contribute to rising sea levels, said NASA's top climate scientist, James Hansen.
"Our greatest concern is that loss of Arctic sea ice creates a grave threat of passing two other tipping points: the potential instability of the Greenland ice sheet and methane hydrates," Hansen said. "These latter two tipping points would have consequences that are practically irreversible on time scales of relevance to humanity."
The United Nations estimates the Greenland ice sheet contains enough water to raise global sea levels by about 23 feet, though melting would take thousands of years.
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