An adult bowhead whale and calf swim through sea ice in the Arctic Ocean. (Photo: Corey Accardo/NOAA)

The Arctic is the final frontier of the oil era. Overused oil fields around the planet are dwindling, tempting energy firms to tap the top of the planet despite its hostile environment. An estimated 13 percent of Earth's undiscovered oil lies underneath the Arctic, totaling about 90 billion barrels. At our current rate of consumption, that would be enough to meet worldwide demand for about three years.

Russia broke the ice, so to speak, in 2013 with its Prirazlomnaya project, the world's first stationary oil-drilling platform in the Arctic Ocean. Oil companies are also vying to drill in Arctic waters off Canada, Greenland and Norway, although fickle oil prices have dampened some enthusiasm lately.

In the U.S., Royal Dutch Shell has has spent nearly $6 billion since 2005 on leases, permits and lawsuits in its quest for Alaska's oil-rich Beaufort and Chukchi seas. That quest suffered a string of setbacks in 2012 — most notably when its Kulluk drilling rig ran aground off Kodiak Island — but Shell hasn't given up. And this week, U.S. regulators rewarded Shell's determination by granting the company conditional approval to begin drilling in the Chukchi Sea.

That marks "a major victory for the petroleum industry and a devastating blow to environmentalists," as the New York Times put it. Why would oil rigs be "devastating" in such a remote part of the world? Here are five of the biggest concerns about trying to extract oil from the Arctic Ocean:

1. The noise.

Even if nothing goes wrong — which history suggests is unlikely — a lot can go wrong.

"[T]here will be unavoidable impacts from each phase of oil development in the Arctic Ocean — seismic exploration, exploration drilling, production platforms, pipelines, terminals and tankers," writes conservation biologist Rick Steiner, a former marine researcher at the University of Alaska who now runs a sustainability consulting project called Oasis Earth.

"The acoustic disturbance to marine mammals from offshore oil development is of particular concern, as underwater noise can affect communication, migration, feeding, mating and other important functions in whales, seals and walrus," he adds. "As well, noise can affect bird and fish migration, feeding and reproduction, and can displace populations from essential habitat areas."

Discontinuous sea ice floats on the Chukchi Sea in September 2013. (Photo: Tom Cronin/USGS)

2. The remoteness.

Remember how hard it was to wrangle the Gulf of Mexico's Deepwater Horizon oil spill five years ago? It took several months, even though it occurred just 40 miles off a more heavily populated and industrialized U.S. coast. The response effort involved mobilizing an armada of vessels, crews and equipment, not to mention coordinating how and when it would all be used.

Now imagine if the spill had occurred off Alaska instead of Louisiana. Even getting the necessary ships and gear to the spill site would be a herculean task. Shell has an official safety plan in case of a spill — including a local stock of tugboats, helicopters and cleanup equipment — but as the Deepwater Horizon illustrated, fail-safes like blowout preventers can fail and pre-spill plans can fall woefully short.

Melt ponds sit atop sea ice in the Chukchi Sea off Alaska's northwestern coast. (Photo: NASA)

3. The sea ice.

Even when response crews do mobilize to clean up an Arctic Ocean oil spill, their options will be limited. As the World Wildlife Fund points out, "there is no proven effective method for containing and cleaning up an oil spill in icy water." Dispersants helped break up the Deepwater Horizon spill in 2010, but they also proved dangerous in their own right, with a 2012 study suggesting they made the oil 52 times more toxic to wildlife. On top of its remote location, the Chukchi Sea is frequented by chunks of sea ice for most of the year. That can make navigation difficult, not to mention oil-spill cleanup.

"A major spill in the Arctic would travel with currents, in and under sea ice during ice season," Steiner writes, "and it would be virtually impossible to contain or recover."

4. The slow ecological recovery.

As bad as the 2010 Deepwater Horizon spill was, at least it occurred in a large, warm gulf populated by microbes that can eat oil. The Arctic Ocean, on the other hand, has low temperatures and limited sunlight, making an oil spill more likely to fester — as seen after the Exxon Valdez spill in 1989.

"A large spill would undoubtedly cause extensive acute mortality in plankton, fish, birds and marine mammals," according to Steiner. "[T]here would be significant chronic, sub-lethal injury to organisms — physiological damage, altered feeding behavior and reproduction, genetic injury, etc. — that would reduce the overall viability of populations. There could be a permanent reduction in certain populations, and for threatened or endangered species, a spill could tip them into extinction. With low temperatures and slow degradation rates, oil would persist in the Arctic environment for decades."

Gas flaring can produce particulate matter that's bad for Arctic ice as well as human health. (Photo: Ken Doerr [CC BY 2.0]/Flickr)

5. The emissions.

In addition to 90 billion barrels of oil, the Arctic may hold as much as 1.7 trillion cubic feet of natural gas — about 30 percent of the planet's undiscovered supply. Natural gas is harder to transport than oil, requiring either pipelines or facilities that convert it to liquefied natural gas (LNG), at which point it can be shipped by tankers. That kind of infrastructure is sparse in the Arctic, so offshore rigs might be more likely to burn off the extra natural gas on-site, a process known as flaring. That's better than letting the gas escape, since methane is a potent greenhouse gas, but flaring can produce other pollutants like black carbon, which causes snow and ice to melt more quickly by absorbing more heat.

Flaring can also cause more direct problems, says Rosemary Ahtuangaruak, an environmental justice advisor for the Alaska Wilderness League in Barrow, Alaska. Ahtuangaruak began working in Barrow as a community health aide in 1986, when a boom in onshore oil drilling — and gas flaring — was associated with a spike in health problems. "One of the things we saw right away were the respiratory illnesses," she tells MNN. "On nights when there were many natural gas flares, I was only getting a couple hours of sleep because of all the patients coming into the clinic."

Oil drilling also brought benefits like running water and better medical care, Ahtuangaruak says, but the influx of patients convinced her the negatives outweighed the positives. And on top of that, oil booms have a long association with social problems like crime, she notes. "Our national energy policy should not cost the health and safety of people who live where the oil and gas development is going to occur."

Of course, any new oil or gas drilling also poses a much broader public-health problem: climate change. Every barrel of oil removed from the Arctic Ocean will presumably be burned, releasing carbon dioxide that will spend centuries trapping solar heat in the atmosphere. Burning the Arctic Ocean's oil could release an additional 15.8 billion tons of CO2 into the atmosphere, which is equivalent to all U.S. transportation emissions over a nine-year period. It would raise global CO2 levels by 7.44 parts per million (ppm), nearly 10 percent of the global rise in atmospheric CO2 over the past 50 years.

Earth's air already has more CO2 than ever before in human history — recently reaching 400 ppm for the first time since the Pliocene Epoch — and it's growing at an unprecedented pace. Not only would Arctic Ocean drilling release more CO2, but any new long-term commitment to fossil fuels slows down the inevitable transition to climate-friendly renewable energy.

"Society faces a fundamental choice with the Arctic," Steiner writes. "Let's hope we choose wisely."