• The Arctic is rapidly changing from the climate crisis, with no "new normal," scientists warn.
• Wildfires and permafrost thaw are making the tundra emit more carbon than it absorbs.
• From beaver invasions to giant holes, drastic changes in the Arctic are affecting the entire planet.

From Alaska to Siberia, the Arctic is changing so rapidly that there is no "normal" there now, scientists warn. The consequences reach across the globe.

The Arctic tundra now releases more carbon than it naturally draws down from the sky, as wildfires burn down its trees and permafrost thaw releases potent gases from its soil.

Once-brown regions are turning green with vegetation, while green areas are turning brown and barren. Sea ice and herds of caribou are disappearing.

This summer was the wettest on record for the Arctic overall, as rain is becoming more common than snow in some areas. Region by region, though, rainfall and the snow season are knocking down both high and low records.

Decades of data on "vital signs" suggest that "the Arctic exists now within a new regime, in which conditions year after year are substantially different than just a couple of decades ago," Twila Moon, a scientist at the National Snow and Ice Data Center, said in a briefing on Tuesday.

"Climate change is not bringing about a new normal," she added. "Instead, climate change is bringing ongoing and rapid change."

That's because the Arctic is warming about four times faster than the rest of the planet, according to previous research.

The increase in average temperatures is changing weather and landscapes in the Arctic, speeding up the climate crisis worldwide.

Giant holes, beaver invasions, and polar wildfires

For example, beavers are moving into Alaska's tundra and transforming its waterways with their dams, as warmer conditions have brought more wooded, comfortable riverbanks for them.

In Siberia, a giant hole in the ground is rapidly growing because the permafrost — a layer of soil that used to be permanently frozen — is thawing.

That's an extreme example, but melt and thaw is happening all over the planet's northernmost regions. Combined with drastic swings in weather year-to-year, these changes are wreaking havoc on Arctic landscapes, ecosystems, and people.

"These dramatic differences are making it difficult for communities to plan and they create safety issues for people who are used to more stable ice, snow, and temperature," Moon said.

She was presenting the Arctic Report Card, an update that the National Oceanic and Atmospheric Administration publishes each year, at the fall meeting of the American Geophysical Union.

This year's report revealed a crucial shift in northern landscapes: The Arctic tundra is no longer a net carbon sink, with its boreal forests pulling carbon dioxide from the sky. Now it's a net source of carbon emissions.

"This transition from a carbon sink to a source is of global concern," Brendan Rogers, a scientist studying the tundra at the Woodwell Climate Research Center, said in the briefing.

He added that the tundra's carbon emissions are relatively small for now, "but it's that transition that we're concerned about."

This shift is partly due to giant polar wildfires burning down tundra vegetation and all the carbon it's stored. It's also because of permafrost thaw, which releases large amounts of methane — a heat-trapping gas more potent than carbon dioxide — as bacteria in the soil digest thawing plant matter.

Meanwhile, rising Arctic temperatures are driving ice melt, including on the Greenland Ice Sheet, which is a major contributor to sea-level rise worldwide. Rising oceans are already increasing flooding in coastal cities across the planet.

For example, US coastal cities from Boston to San Diego have seen more and more flood days per year every decade since 1950, according to the Environmental Protection Agency.

Arctic science is more important than ever

Reporters asked the NOAA scientists about the incoming Trump administration and whether they were concerned about losing funding for their Arctic research.

"The need, the requirement, the demand signal if you will, is higher than ever before," Richard Spinrad, the NOAA Administrator, said in the briefing.

Changes in extreme weather and sea level across the globe show that "there's a need for these investments to increase right now," he said, adding that studies have shown "the return on those investments is extraordinary, in many cases 10 to 1 in terms of protection of lives and property."

• Parts of Siberia's landscape are a ticking time bomb.
• Giant craters started mysteriously appearing 10 years ago.
• A team of scientists think they finally know why.

Tucked away in the frigid northern corner of Siberia are giant craters, some deep enough to fit a 15-story building. Scientists observed the first crater in 2014 and have found about 20 more in the years since.

It's been fairly clear from the beginning that the craters are caused by some type of explosion deep underground. What's triggering the explosions is a topic of debate — one that Ana Morgado, a chemical engineer at the University of Cambridge, thinks she and her colleagues have settled.

If their theory is correct, it would mean these types of exploding craters are rare and only form under specific geologic conditions, so there's no risk of something similar showing up in, say, downtown Manhattan.

Their theory also ties these massive eruptions to climate change. As the planet continues to warm, more craters will likely erupt. When this happens, it releases a highly potent greenhouse gas into the atmosphere, which in turn contributes to climate change.

The mysterious case of Siberia's exploding craters

The colder nooks of the world, in places like Siberia and northern Canada, have a subsurface layer of soil called permafrost that's been permanently frozen for millennia. As global temperatures climb, pockets of permafrost are thawing worldwide.

This has led to some spectacular discoveries like a perfectly preserved 30,000-year-old squirrel in Canada and a 46,000 year-old worm in Siberia. It's not just ancient squirrels and worms hiding in permafrost.

Concentrated amounts of the highly explosive greenhouse gas methane are trapped deep underground in the permafrost in ice-like solids called methane hydrates.

Researchers widely agreed that when these hydrates are damaged, they release methane gas, which is what's triggering the explosions in Siberia.

How the hydrates are damaged in the first place, though, is less clear.

Existing theories suggest that warming permafrost, as a result of the warming Arctic, could ultimately destabilize the hydrate layer, releasing explosive methane gas.

"That was the initial idea, and we didn't question it at all at the beginning," Morgado told Business Insider. "What we questioned was that: Okay, you're saying that that is the case, but you don't present a physical model that can explain that. So no math."

When the team tried matching the math with the observations, they found that it would take centuries for the process to trigger an explosion. The Arctic had only been significantly warming over decades.

"So either something else was happening or magnifying this effect," Morgado said in an email.

The team found the missing piece to their puzzle when they learned of past geological surveys that had identified pools of liquid water, called cryopegs, just above the methane hydrates in Siberia.

What's causing the ground to erupt in Siberia

Normally, the cryopegs are stable. Morgado and the team realized that the summer would threaten this stability.

In summer, frozen soil at the surface melts. That meltwater is then pulled down toward the cryopegs via a process called osmosis — the same process that helps water climb against gravity through tall plants.

Osomis was the magnifying effect the researchers were looking for.

With longer, warmer summers in recent years, enough meltwater is available for long enough periods that it's being driven down to the cryopegs on timescales that matched the observations, Morgado said.

Once the meltwater reaches the cryopegs, it's over.

The meltwater increases the pressure inside the cryopegs, just like adding more water to a water balloon. That pressure cracks the soil leading to the surface, which triggers a drastic reverse in pressure. And that pressure change is what damages the methane hydrates, triggering an explosion.

More exploding craters to come

Siberia will likely have more explosive craters in the coming years as global temperatures continue to warm. That's a problem because the methane these explosions release is a highly potent greenhouse gas, which helps drive global temperatures up even more.

It's unclear exactly how much methane these explosions release, but in the grand scheme of climate change, they're a small matter. Thawing permafrost is a larger concern because it contains concentrations of not only methane but also carbon dioxide that is released into the atmosphere when it melts.

Siberia isn't the only place in the world with permafrost.

If the team's theory is correct, it's possible, but unlikely, that other places with permafrost will start erupting the way Siberia has, Morgado said.

"It would need to be very specific that you would have this in another place," Morgado said, adding, "Luckily we are not seeing the entire world, or the entire Arctic, bursting into craters."