Summer on the Chukchi Sea is pleasant for only a select few: the rugged polar bears, walruses, and whales that live on and under its seasonal islands of ice, built to brave the pounding wind and currents. This body of water, which separates northern Alaska from Siberia, may seem desolate, but its inhabitants will soon have company.

Drill rigs may arrive in the Chukchi as early as this summer, as Royal Dutch Shell is betting it can successfully—and safely—extract oil from beneath its cold, choppy waters. On Monday, the U.S. government effectively gave Shell a green light. (Final confirmation won’t come until various drilling permits, including one for disturbing marine mammals, are granted, but those are very likely to come through.) “Sea ice permitting, the earliest date exploration may begin offshore Alaska is July 15,” says Curtis Smith, a spokesman for Shell.

There are likely at least 4 billion barrels of oil hiding there. (For comparison, the U.S. produces a little more than 3 billion barrels of crude oil each year.) The Arctic Ocean, which includes the Chukchi, is estimated to contain 13 percent of the world’s untapped oil and holds a treasure waiting for whoever can reach it. But environmentalists are trying to stop what they consider to be the exploitation of an unspoiled sea and a seasonal sanctuary for wildlife.

“They’re drilling in one of the most important late-summer refuges,” says Margaret Williams, the managing director of the Arctic Program of the World Wildlife Fund. She says the Chukchi Sea is home to half of all U.S. polar bears and is an important habitat for many at-risk animals, including endangered humpback whales.

Shell has been eyeing the Chukchi Sea since at least 2008, when it paid the U.S. government $2.1 billion for the rights to drill there and in several other areas of the Arctic. That deal secured Shell’s claim to the Chukchi, but didn’t guarantee that its drilling application would be approved by the government. Shell’s prospects started looking promising when, after a long legal fight with environmentalists, the federal Bureau of Ocean Energy Management (BOEM) published an Environmental Impact Statement (EIS) for the project in mid-February.

The EIS, an official government analysis of the environmental consequences of drilling in the Chukchi, acknowledged the possibility of a major spill—defined as a loss of more than 1,000 barrels—happening sometime in the next 75 years if Shell were to move beyond the exploratory drilling it has planned for the summer. But the agency ultimately concluded that drilling would cause “no significant impact” to the region and approved Shell’s formal application to drill in the Arctic. (While catastrophes are the exception rather than the rule, the BOEM did estimate that BP’s Deepwater Horizon operation would spill less than 5,000 barrels of oil before its 2010 disaster released 4.9 million barrels into the Gulf of Mexico.)

Shell’s no stranger to the risks of Arctic drilling. The company explored the Chukchi in 2012, its first time drilling in the Arctic in two decades. That attempt failed as one of its drilling rigs ran ashore in the Kodiak archipelago. Shell’s mistake was moving the rig from Alaskan waters in the frozen final days of December to avoid getting taxed at the start of the new year, according to the Coast Guard’s report for the incident. When Shell’s drill ship was placed into rough waters, it was juggled by waves before breaking free of its tow ship and running aground. The accident appears to have been avoidable, because workers knew from the beginning that the move was dangerous: The tow ship master had warned the drill ship operator, "To be blunt I believe that this length of tow, at this time of year, in this location, with our current routing guarantees an ass kicking.”

Another incident could result in the loss of more than just a $200 million drilling ship. In the Arctic, an oil spill would be hard to control. A frozen sea makes it especially difficult for oil to be cleaned up properly, since petroleum sticks to ice. While oil in warm, well-stirred areas like the Gulf of Mexico can be degraded by microbes, it’s likely too much to handle for Arctic bacteria, which have not evolved the need to chew through oil, says Alexander Horne, a professor emeritus of ecological engineering at UC Berkeley. A Chukchi spill would have more long-term effects than BP’s Deepwater Horizon disaster, he says.

And with winds sweeping at 30 to 50 miles per hour over a mix of freezing water and pack ice, any attempt to purge spilled oil would practically be a lost cause. “When you have ice storms and incredible fog, it’s hard to detect oil in the Arctic,” explains Williams, of the World Wildlife Fund.

One remedy would be trying to contain the gusher or divert it to another well, but if that didn’t work, Shell workers would likely turn to a product resembling dish soap as another way to neutralize some of the escaped oil. “Dispersants similar to what we use to clean our dinner dishes could be injected into the oil in an attempt to disperse it, making it less damaging to the environment,” says Robert Bea, a risk-management consultant and a professor emeritus of environmental engineering at the University of California, Berkeley. “But potentially, thousands of gallons of dispersant would have to be injected. It’s all a challenge of logistics, and it’s particularly daunting here because we are more than 1,000 miles from the nearest harbor. There isn’t a nearby Home Depot to help with the logistics.”

Dispersants could only be used for summer oil spills, when there is less ice. But years down the line, when Shell completes its initial summer exploratory stages, steady production will likely occur year-round in icy conditions. In winter, especially, any spilled oil would have far-reaching consequences, experts say. “Oil that escapes goes to the bottom of the ice, and ice is not steady. It’s moving with the ocean current,” says Bea. “This ice with oil gas trapped under it would be incorporated into the Arctic Gyre and that would move around the Arctic area. Some of the pollution would reach Russia, Canada, and Norway.”

In an extremely cold sea, liquids take longer to disappear through evaporation or dilution. That’s why a circulating vortex of oil would be not just lost profits for Shell, but a major risk to Arctic wildlife. Crude oil contains certain elements that, when it’s spilled, may stick around long enough to damage fish gills before evaporating or diluting, says Horne, the Berkeley professor. As bad as the gill damage would be, even worse effects on marine life would likely come from the toxic and corrosive phenols in oil. “You could jump in a barrel of oil and you’d be oily-looking. If you jumped in a barrel of [pure] phenol, you’d be dead within minutes,” Horne says.

Shell, for its part, thinks it can get the job done safely. “We have put in place an environmentally sensitive, thoroughly responsible plan for exploration offshore Alaska,” says Curtis, the company spokesman. “We wouldn’t consider moving forward with anything less. No company in the world has assembled the Arctic oil-spill response and containment assets that Shell has. We look forward to never using them.”

Robert Bea knows about the inhospitable Arctic firsthand—and feet. “My feet got so cold that we would bring hair dryers on board, plug them into electric outlets, [then] into our boots and gloves,” says Bea. He worked for Shell as a drill rig worker in the 1960s, later rising through the ranks to help engineer Shell’s first Arctic oil-and-gas platform. Even Bea, who has worked with and for the oil industry for 55 years, wonders if the Arctic is ready for such a drastic change. “Have we really worried enough about the potential of a catastrophic blowout?” he asks. “Have we learned enough about the prevention and mitigation of spills? At this point it’s an unanswered question.”