On June 19, 2015, Mats Granskog and his 35 crewmates found themselves drifting slowly southwestward, toward the edge of the Arctic Ocean’s floating lid of sea ice. The R/V Lance, their sturdy former sealing boat and now a Norwegian research vessel, was hitching a ride in an ice floe about a kilometer across. They were about as far from the North Pole as San Francisco is from Portland, Oregon.

Granskog, a sturdy 43-year-old of Finnish origin, is chief scientist in an unusual and ambitious effort to study the full life cycle of Arctic sea ice, from its formation in winter to melt-out in summer. He and his colleagues on the Norwegian Young Sea Ice Cruise, or N-ICE2015, hoped they would gain new insights into what some experts are calling the “new Arctic,” a region that’s feeling the brunt of human-caused climate change more intensely than any other.

Shifting sea ice can crush a boat, so mariners don’t typically freeze themselves into it on purpose. But that’s precisely what the crew of the Lance had done that January, in the dead of the polar night.

With just a small bubble of illumination from the boat, they had managed to unload tons of equipment onto the ice: scooters, sheds, buoys, ice drills, a tent, and a 33-foot-tall weather mast. As the expedition progressed, they endured violent storms and temperatures plunging below minus 40 degrees Fahrenheit.

“There was also the threat that a hungry polar bear comes along and wants to chew on your equipment, or your leg,” Granskog recalls, with a hint of a smile. “We had a few close encounters in the dark, nothing serious, but of course it was a reminder that we are not the king in this place.”

By June 19, with the late spring sun doing a lazy 360 around the sky, they could at least see the polar bears coming. And conditions had improved considerably, with temperatures hovering around freezing. After breakfast, several crew members were preparing to head out onto the ice to squeeze in some final scientific work. The Lance would soon head for port in Svalbard, about a day’s cruise to the south.

Sea ice can melt quickly in June—especially these days, with global warming leaving the frozen layer much thinner and less extensive than it used to be. “We’re losing the sea ice,” observes Mark Serreze, director of the National Snow and Ice Data Center.

Studies suggest that the decline in summer Arctic sea ice has been steeper since the late 20th century than at any time in the past 1,450 years. Serreze predicts that within the next couple of decades, human-caused warming will leave the Arctic with no significant summer sea ice cover.

The melting ice has already turned the region into something of a new frontier, with many nations eyeing its sea routes, its strategic position between Eurasia and North America, and its potentially huge reserves of oil and gas. Indeed, the area north of the Arctic Circle may harbor an estimated 90 billion barrels of oil and 1,670 trillion cubic feet of natural gas, as well as 44 billion barrels of technically recoverable natural gas liquids. This amounts to 22 percent of the world’s undiscovered stores of these fuels. All that from an area comprising just 6 percent of Earth’s surface, according to a U.S. Geological Survey assessment.

And herein lies the polar paradox: As global warming from burning fossil fuels and other human activities causes sea ice to shrink, it helps open the Arctic to offshore fossil fuel exploration. Should large amounts be discovered and burned, it will be all the more challenging to meet the Paris Agreement goal to keep the rise in global temperatures this century well below 2 degrees Celsius, or 3.6 degrees Fahrenheit—and to limit the already-significant impact on this and other regions. Meeting that goal was a stretch even before reports today suggested that President Donald Trump would pull the United States out of the accord. This latest move—and the burning of Arctic fossil fuel resources made accessible by continued warming—would likely put the 2 degree Celsius limit well out of reach.

Russia and Norway are already drilling in their own Arctic waters. So far, the output is relatively modest. Russia’s single Arctic offshore operation produced just 2.1 million tons of oil in 2016, which is not even enough to cover a single day’s consumption of petroleum in the U.S. But Arctic oil output could grow significantly in the coming years. And Moscow is definitely dreaming big. The country is laying claim, via peaceful means through the United Nations, to a vast swath of offshore territory—for exclusive rights to drilling, as well as fishing and other economic activities.

Russia also seems to have placed an iron fist into the velvet glove of its legal claim. In recent years, the nation has staged a major military buildup in the Arctic—more than what’s necessary for simple defense, says Heather A. Conley, a specialist in Arctic affairs at the Center for Strategic and International Studies. She argues that Moscow is trying to bring down an “ice curtain” in the region. While the Iron Curtain of the Cold War excluded citizens of the Soviet Union and its satellites from contact with the West, the ice curtain appears aimed at a different kind of exclusion: denying other nations access to large swaths of the Arctic.

Conley believes there’s a window of opportunity to prevent confrontation. “But windows can close,” she says.

The Arctic “is not only a potential environmental and ecological disaster,” Sweden’s Foreign Minister, Margot Wallström, told fellow European ministers and others at a conference in Norway earlier this year. Developments in the region “could also well develop into a security threat of global proportions.”

Out on the ice itself, though, the threat facing Granskog was tangible and immediate. He knew the ice could split open instantly, sending his N-ICE2015 researchers and their equipment tumbling into the drink. “Mother Nature is in control,” he says. “You’re walking on a thin piece of ice, and anything can happen.”

As it turned out, he and his colleagues on the Lance would not have to wait long to experience first-hand what can happen in a dramatically warming Arctic.

The crew was under no illusion about what had been happening, literally right beneath their feet. During the expedition, they found that some ice was less than five feet thick—roughly half what it was just a few decades earlier. To explore what was going on below that thin ice, the scientists had been using a remotely operated vehicle. What they discovered startled them.

“Operating an ROV under the ice has lately been like driving in spinach soup,” Granskog wrote in a blog post. “The waters are full of phytoplankton, and zooplankton that are feeding on them, with visibility as low as driving a car during a snow blizzard.”

Phytoplankton are tiny plants, and the foundation of the entire Arctic marine ecosystem. So any changes in the abundance, species composition, geographic range, and life cycles of these algae could have profound effects on Arctic life. You can think of them as the grass of the sea, with zooplankton serving as the cows. These, in turn, feed the Arctic cod (Boreogadus saida), which are eaten by seals, which are the favorite meal of polar bears (Ursus maritimus). Mess with the phytoplankton, and you may well be messing with the bears, too.

Like almost all plants, phytoplankton need sunlight to survive. Yet here were copious blooms of the stuff under ice blanketed in snow up to two feet thick.

The researchers discovered that the increasingly thin and fracture-prone sea ice was to blame. Strong storms broke it open more often than expected—starting way back during the brutally cold and dark winter months. Although the resulting stretches of open water would quickly freeze over, these former “leads,” as scientists call them, were like zippers that subsequent storms could easily reopen.

As the polar skies brightened a bit with the approach of spring, these zippers opened and refroze, and opened again, exposing seawater to life-giving pulses of solar energy. However short these pulses may have been, they were enough to trigger and sustain blooms earlier in the year than normal.

Ordinarily, giant blooms of phytoplankton and zooplankton don’t materialize until later in spring, as sea ice breaks up for good. And the life cycles of species further up the chain are timed to take advantage of that later banquet. But as more and more of the green soup forms under the ice early on, the whole system could be thrown off kilter. For example, the under-ice blooms could deplete nutrients from the water, possibly limiting the later blooms that currently sustain the Arctic food chain. Indeed, N-ICE2015 researchers had found evidence for depletion of nutrients in the water they sampled.

One expert in Arctic marine biology offers a blunt assessment about what’s already happening. Changes to sea ice are leading to “a complete shift in everything we thought about this ecosystem,” says Rolf Gradinger, of the University of Tromsø in Norway.

Consider the zooplankton that eat the phytoplankton. “True Arctic ones are big and fatty, with a lot of energy content,” he points out. This offers excellent nutrition for Arctic cod, baleen whales, seals, and ultimately the polar bears. But as the ice withers further, these Arctic zooplankton could decline and be replaced by more southerly species—containing “much less energy per bite.”

Even as changes in the Arctic are affecting our lives thousands of miles to the south, the region may still seem at the periphery of the world—remote, unconnected, and relatively unimportant. One reason for this perception is that in maps, the Arctic has long been depicted as a broad white swath—”a barren place way up there,” observes Paul Wassmann, an Arctic marine ecologist at Norway’s University of Tromsø. In these maps, “the Arctic is seen as a kind of appendix.”

Now, as the region warms, Wassmann says it would be wise to shift our perspective—literally. Instead of common map projections with the equator running across the middle, consider one that looks straight down on the North Pole. Seen in this way, the Arctic is at the very center of the Northern Hemisphere, with land arrayed at its periphery.

With the exception of the United States, other Arctic nations have embraced this perspective shift. While the Arctic once was seen to be at the fringes of human affairs, Margot Wallström, Sweden’s foreign minister, argues, “this is far from true now—because global developments have put the region at the center of international attention.”

As Sturla Henriksen, CEO of the Norwegian Shipowners’ Association, puts it, “A polar ocean is opening up”—for shipping, as well as extraction of resources such as oil, gas, and fish.

Much of the region is still harsh and unforgiving, and will remain that way for some time. That makes exploiting offshore Arctic resources very expensive. Even so, Arctic bulls are pushing to proceed.

While the use of renewable energy worldwide is projected to grow 1,700 percent by 2050, fossil fuels are still expected to comprise a third of all energy consumption. “It is not important exactly what the number is,” says Karl Eirik Schjøtt-Pedersen, Director General of the Norwegian Oil and Gas Association. “There will still be a significant demand for oil and gas in 2050.”

Between now and then, many existing oil and gas reservoirs will become depleted. (In fact, Norway’s own production has been halved since 2000.) That, Schjøtt-Pedersen and others argue, makes exploring for Arctic oil and gas sensible right now. To those who say the risks are too high in the fragile Arctic environment, he asserts that the Barents Sea in the Norwegian Arctic is less dangerous than the waters off Newfoundland.

“There are no significant climatic barriers which stand in the way of developing new fields in the Barents Sea,” he says.

Norwegian environmentalists vehemently disagree. They argue that the risks to fragile Arctic ecosystems from oil spills far outweigh any benefits. And they say the impact of burning those fossil fuels—yet more warming and climatic disruption—poses a threat that should not be taken lightly.

But the Barents Sea fields alone potentially harbor the equivalent of 17 billion barrels of oil. And that’s proving irresistible to the Norwegian government. Just this past March, the country announced preliminary plans to open a record number of blocks for oil and gas exploration in its portion of the Barents.

As much as Norway is focusing on developing the Arctic, Russia is going even further. In 2015, the country filed a territorial claim with the United Nations for 463,000 square miles of the Arctic, including the North Pole. That’s an area three quarters the size of Alaska. Russia says geological surveying proves that the continental shelf extends from their northern coast across all of that oceanic territory. If the U.N. accepts the petition (by no means a foregone conclusion), Russia will gain exclusive economic control of resources in those waters and the seabed beneath.

This attempt is not new. It originates with Stalin. But Moscow may now have the science to support its claim, which was made under a treaty called the United Nations Convention on the Law of the Sea. Under UNCLOS, Denmark also claims a swath of the Arctic. Canada is expected to formally file as well, in 2018.

Meanwhile, the United States hasn’t even ratified the Law of the Sea—the only Arctic nation not to do so. Republicans in the U.S. Senate have prevented ratification for years, arguing that treaties like this undermine U.S. sovereignty.

The Russians see the Law of the Sea from a different perspective—as a way to dramatically extend their economic sovereignty.

Russia has pressed its claim while “following the rules,” says Conley of the Center for Strategic and International Studies. They see riches to be harvested, and they’re more likely to reap them this way.

Those riches may lie surprisingly far over their northern horizon. Last January, a Russian scientist named Gennady Ivanov briefed attendees at the appropriately named Arctic Frontiers conference in Norway on what his company has discovered about the seafloor geology around the North Pole: “I assure you,” he said excitedly, “there is oil and gas there.”

Vladimir Barbin, the nation’s senior official dealing with the region, declared that “Russia’s future is linked to the Arctic.” Already, it provides 10 percent of Russia’s GDP (although other estimates put it as high as 20 percent). “In the future, it will be even more significant,” Barbin said. “Russia must use available Arctic resources ‘so that we can benefit the development of the country.'”

To help with economic development, Russia is building 10 search and rescue centers along the Northern Sea Route, the Eurasian equivalent of the famed Northwest Passage. This move is part of a push to improve support infrastructure along a shipping route that can cut the journey between Europe and Asia by a third.

With just 50 ships, give or take, making the passage each summer, the route currently handles only a trickle of traffic. But as the ice retreats, more ships will be tempted to make the journey. And already for Russia, portions of the route are proving crucial for moving people and material involved in developing Arctic oil and gas resources.

The new stations also have military capabilities that go beyond what’s needed for search and rescue, says Conley. And this is just part of the ice curtain strategy. Russian officials have created a new strategic command for the region. They also plan to reopen 50 Arctic military bases by 2020. Already, Russia has been conducting large military exercises there, involving not just conventional but also nuclear forces. In February 2015, for example, nuclear units of the Russian Navy conducted exercises beneath the North Pole. (Russia is also developing mobile nuclear power plants that can provide electricity to its Arctic military forces.)

One of the most striking military exercises occurred in March of 2015. Russian President Vladimir Putin called the Northern Fleet to full combat readiness in a snap Arctic exercise involving more than 45,000 troops, 41 warships, 15 submarines, and 110 aircraft. But perhaps the most unsettling aspect was that Russia gave no notification to NATO, as is customary with exercises like this.

“Clearly, this is about global power projection capabilities, and the Arctic is a strategic location,” Conley observed at an event in early 2016. “We knew that from the Cold War era, and it exists today. The U.S. doesn’t view it that way, but Russia certainly does.”

It has all the hallmarks of a military strategy known as “anti-access/area denial,” or A2/AD, she believes. Simply put, A2/AD is intended to protect friendly military forces while preventing adversaries from securing potentially advantageous positions. Russia also sees the Arctic as providing strategic access for its Northern Fleet to enter the Atlantic and Pacific Oceans.

“With its strong national Arctic identity and the location of its strategic nuclear deterrent in the Far North, Russia views itself as the Arctic superpower, as the Kremlin is increasingly willing to use the Arctic to demonstrate Russia’s return to power on the global stage and in the region,” Conley and a colleague conclude in a paper titled “The New Ice Curtain.”

Meanwhile, the U.S. has just two icebreakers compared to Russia’s 41. “Most Americans do not even know that they are an Arctic nation,” Conley says.

And while Russia and other Arctic countries are fully aware of how warming is transforming the region—and are attempting to take full advantage of it—President Donald Trump continues to deny that global warming is even taking place, and has begun demolishing U.S. policies to reduce the carbon emissions causing it.

Just as Arctic ecosystems will have winners and losers thanks to climate change, so will the nations of the world. And from that climatic perspective, Russia’s efforts in the high north make sense, according to James White, a climate scientist who directs the Institute of Arctic and Alpine Research at the University of Colorado. “Russia is the biggest beneficiary of a warmer planet,” he says.