Cape Morris Jesup in Greenland is just about the northernmost piece of land on planet Earth. It’s located just 400 miles south of the North Pole, on Greenland’s craggy, desolate north shore. This is a place so far north that the sun doesn’t rise for most of the winter months.

In February, in the dark of winter, Cape Morris Jesup’s weather station recorded nearly 60 hours of temperatures above freezing — a new record. On February 24, the temperature reached a high of 43 degrees Fahrenheit.

Think of it like this: On February 24, you could be standing on the northernmost bit of land in the entire world, in darkness, in shorts and a T-shirt. That you wouldn’t quickly die is astounding because the cape’s temperatures are usually closer to minus 30 degrees in February.

It’s often said that on this warming planet, nowhere is changing faster than the Arctic. But this winter is providing stunning new evidence of a region in extraordinary, worrying flux.

On Friday, we got another bit of evidence this is true: The National Snow and Ice Data center announced that this winter’s Arctic ice maximum was among the smallest in history.

During the winter months, the polar ice cap grow and grows. But this year, it’s final size covered an area 448,000 square miles less than the 1981-2010 average. “The four lowest seasonal maxima have all occurred during the last four years,” the NSIDC reports.

That’s a truly troubling trend. Less ice in the Arctic triggers a feedback loop. The less ice, the more solar radiation is absorbed into the ocean. And that makes the region even warmer, and leads to even smaller amounts of ice.

It’s also a hint of the future to come: an Arctic Ocean that’s not permanently frozen and all the disastrous consequences that come with that.

Here are five of the most alarming observations of the Arctic from the beginning of this year. (Also check out a Today, Explained episode on this topic.)

1) It was the warmest Arctic winter on record

Overall, this winter (as measured by December, January, and February, the three coldest months) was the warmest on record. As the Associated Press reported, Arctic weather stations averaged 8.8 degrees Fahrenheit above normal.

These Arctic warm spells do occur due to natural variability, Alek Petty, a NASA polar scientist, says. “But the key is that they are happening more frequently, they are lasting longer, and they have been more intense than they used to be,” he says. Indeed, this was the third Arctic winter in a row that experienced an extreme heat wave.

2) There’s new evidence that weird weather in the Arctic impacts our weather

Earlier in March, Nature Communications published a study looking at temperatures in the Arctic and in North America from 1950 to 2016. And it found a correlation: When the Arctic is weirdly warm, it tends to be weirdly cold and snowy down here in the continental United States, particularly on the East Coast. We saw this pattern on display this year. If you can think back to New Year’s Eve, it was well below 0 degrees Fahrenheit in some places on the US East Coast. Meanwhile, it was around 30 degrees in Alaska.

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Climate scientists still don’t know what causes this pattern or whether it’s becoming more common due to climate change. One (unproven) hypothesis is that a warming Arctic decreases the strength of the jet stream. This air current acts like a tourniquet keeping Arctic air from bleeding out over North America. It’s also hard to say what the direction of the correlation is. Is the Arctic weather impacting the weather down south, or the other way around, or a little bit of both? (The researchers in the Nature Communications paper suspect it’s the Arctic that’s driving the trend. But it’s not conclusive.)

Whatever the cause, know this: Weather is global. And when the Arctic becomes weirdly warm, the consequences can hit close to home.

3) There were record-low amounts of ice, continuing a decades-long downward trend

There’s no land at the North Pole — it’s a frozen ocean. One of the most spectacular yearly cycles on Earth is the freezing and thawing of huge swaths of this ocean. Throughout the winter months, the ice cap doubles in size from nearly 3 million square miles to nearly 6 million.

Here’s NASA’s illustration of what the sea ice extent looked like in 2015 through the early months of 2016. It’s a beautiful reminder of how the seasons transform the land and life on it.

Every year, polar scientists measure the extent of the sea ice during winter. That is: how much area in the Arctic Ocean gets frozen over. And every year, on average, that area gets smaller and smaller.

The record low was last year. The second lowest was this year. 2016 and 2015 are virtually tied for third. This trend shows no sign of reversing.

In the following chart of sea ice extents, you can clearly see how the average maximum winter sea ice declines every decade.

The record-low levels of ice also led to another Arctic first: For the first time ever, a ship was able to navigate the Arctic Ocean north of Russia during wintertime. This milestone is partly due to technical advances in shipbuilding. But it’s also due to the fact that there was less ice in the waters this year, and that the ice that remained was thin enough for the ship to break through.

In its most recent Arctic Report Card — an annual assessment of the Arctic environment — NOAA concluded that the region “shows no sign of returning to [the] reliably frozen region of recent past decades.” This winter showed this trend is not letting up anytime soon.

The loss of winter sea ice, Petty says, “reinforces the message that we’re radically changing the climate system.”

4) Scientists saw unsettling signs that the remaining ice is getting thinner and less stable

A big conclusion from NOAA’s last Arctic Report Card was that not only is the Arctic’s ice sheet shrinking but what ice remains is growing less stable. In 1985, 45 percent of the ice in the Arctic was more than a year old. In 2017, that figure was down to 21 percent. Younger ice is thinner than older ice and more susceptible to changes in temperature, and to melting. Thinning ice makes life tougher for polar bears, which travel on ice sheets to find food.

And this winter, polar scientists saw something unheard of happening to some of the oldest, thickest ice left. In late February, satellite images showed a hole in the ice (i.e., exposed water) just north of Greenland. That’s where scientists expect the ice “to be at its thickest and most stable,” Petty says. Yet this winter, winds were able to push it offshore. Scientists don’t expect this area to be ice-free in the summer. And they’re currently unsure if such a hole has ever been observed before during the winter.

The northerly warm airflow opened up the sea ice north of Greenland. This large open water area is very unusual. I haven't seen a similar event like this before in the almost 25 years I now work with satellite data. pic.twitter.com/RJcONASaO4 — Lars Kaleschke (@seaice_de) February 26, 2018

Melting sea ice does not contribute much to sea level rise. Watch an ice cube melt in a glass of water — the water level won’t rise because ice is less dense than water. And when it melts, it just fills in the exact area it displaced while solid. (This is basically true for what happens when the polar ice caps melt. But because freshwater is less dense than salt water, when the fresh water in the Arctic ice melts, it does raise the sea level by a tiny bit.)

More importantly, the melting sea ice does impact something that contributes greatly to sea level rise: land ice. As the sea surface melts, it grows darker, which traps more heat, causing more melting. That leads to warming in the whole region. And that’s critical — because sitting on top of Greenland is an enormous ice sheet. If this land ice melts into the water, it will cause a global sea level rise. If all of it melts, scientists estimate, the sea level will be 25 feet higher.

And as polar scientists observe declines in Arctic sea ice, they’re witnessing a concurrent acceleration of melting in some parts of Greenland, as Vox has reported.

5) An “ice-free Arctic” could come within decades

Arctic sea ice extent has been measured by satellites since the 1970s. So while climate scientist suspect we’re witnessing the greatest decline in Arctic sea ice in human history, it’s hard to prove conclusively.

Yet scientists can make some guesses about historical ice extent by sampling ice cores, permafrost records, and tree rings. In the latest Arctic Report Card, NOAA included this chart, which plots the estimated sea ice area for the past 1,500 years. And, well, it looks a little scary.

In a few decades, polar scientists predict that the Arctic will become virtually ice-free, with less than a million square kilometers of ice (a bit larger than the size of Texas) during the peak of summer. This has a lot of geopolitical consequences, as Vox’s Johnny Harris explained in a documentary. Russia is now positioning itself to be the dominant country when it comes to shipping routes in the Arctic Ocean.

This winter was extreme. And it only suggests that this “ice-free” Arctic may arrive sooner than later.

“If you project forward in time using climate models ... that’s suggesting timelines of 20 or 30 years for an ice-free arctic,” Petty says. “But these strong changes we’re seeing in winter … might mean this can happen a lot earlier than these projections suggest.”