Story highlights Mayor says "it will only be a matter of time before something happens out there"

Shell says it has started drilling in the Chukchi Sea off Alaska's North Slope

The Obama administration approved preparatory work in late August

Shell says it's capable of handling a big oil spill; environmentalists aren't so sure

Royal Dutch Shell has begun preparatory drilling for an offshore oil well in the Arctic, the oil company announced Sunday, the first step in a long-controversial project.

U.S. authorities granted Shell permission to begin work on the well in the Chukchi Sea, about 90 miles off the Alaskan North Slope, in late August.

"Today marks the culmination of Shell's six-year effort to explore for potentially significant oil and gas reserves, which are believed to lie under Alaska's Outer Continental Shelf," company spokesman Curtis Smith said in a writen statement. "In the days to come, drilling will continue in the Chukchi Sea, and we will prepare for drilling to commence in the Beaufort Sea."

Steve Oomittuk, the mayor of nearby Point Hope, said he's keeping a wary eye on the Shell operation and has concerns about what the future will bring.

"There's nothing we can do now but I worry about the weather and the animals we depend on for our survival," he said. If "Shell finds what it thinks is down there then many other companies are going to come and then it will only be a matter of time before something happens out there."

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The Obama administration gave Shell the green light to start "certain limited preparatory activities," including work related to the installation of a blowout preventer, on August 30. The government had been set to approve new drilling in Arctic waters off Alaska before BP's disastrous 2010 oil spill in the Gulf of Mexico prompted a review of existing plans.

That blowout at a BP well off Louisiana killed 11 workers, took nearly three months to cap and became the worst oil spill in U.S. history. Shell says it has taken steps "to do it right" in the Arctic, where the U.S. Geological Survey estimates more than 90 billion barrels of oil and nearly 1,700 trillion cubic feet of natural gas may be recoverable.

The shrinking of the region's sea ice -- which hit record lows this year -- has created new opportunities for energy exploration in the region. But environmental groups argue that Shell has failed to show it can handle a spill in the inhospitable region, roughly 700 miles north of Anchorage.

"While this is an interim step only, this is like a building inspector letting a developer start construction on a skyscraper on shaky ground before the safety plans are even complete," the environmental advocacy group Sierra Club said in a late August statement critical of the Obama administration. "It's premature, it's unwarranted and it's wrong -- especially when it's happening in one of the most pristine places on earth."

The amount of the Arctic covered by sea ice fell in late August to the lowest point since satellite observations began in 1979, the National Snow and Ice Data Center reported. That trend has stretched into September, with 45% less coverage than September conditions in the 1980s and 1990s.

Climate researchers say this decrease in sea ice a symptom of a warming climate, caused largely by the combustion of carbon-rich fossil fuels. The science is politically controversial but generally accepted as fact by most scientists.