It’s been downright toasty at the North Pole, at least by Arctic standards.

The northernmost weather station in the world, Cape Morris Jesup in Greenland, saw temperatures stay above freezing for almost 24 hours straight last week, and then climb to 43 degrees Fahrenheit (6.1 degrees Celsius) on Saturday before dropping again.

But that Saturday temperature was a whopping 45 degrees Fahrenheit above what’s normal this time of year:

Cape Morris Jesup (#Greenland's northernmost observation station) is now reporting temperatures well above freezing today... +6.1°C at the latest observation! Crazy!



Station is provided by @dmidk at https://t.co/kedfPPAg9q. pic.twitter.com/wEcs4B61mo — Zack Labe (@ZLabe) February 24, 2018

While there are year-to-year variations in Arctic temperatures, it’s concerning that this is the third year in a row where we’ve seen a heat wave during winter, according to Mark Serreze, director of the National Snow and Ice Data Center at the University of Colorado Boulder.

And the heat wave, along with an overall warmer winter, is having a direct impact on the Arctic sea ice that should be at its maximum extent this time of year but is instead at record lows. In January, we saw the lowest extent of Arctic sea ice for this time of year since records began in 1979.

Occasional rapid temperatures spikes are a common weather phenomenon, even in the Arctic. But scientists read the growing frequency — combined with the backdrop of rising overall temperatures — as a strong signal that the climate is changing at a stunningly rapid pace, even faster than they predicted just a few years ago.

We’ve seen an unprecedented pattern of high temperatures in the Arctic in recent years

Even as a cold snap grips Northern Europe and Asia, bringing snow as far south as Rome for the first time in six years and temperatures as low as 5 degrees Fahrenheit in the United Kingdom, it’s actually warmer in parts of the Arctic.

In fact, as you can see in this map of temperature anomalies, many parts of the world are seeing unusual weather right now, both warm and cold:

“The immediate cause of this is clear: You’ve got a jet stream pattern that is allowing all this high-pressure warm air into the Arctic,” Serreze said. The jet stream, a high altitude, and high-speed air current, in turn, helps drive winds closer to the surface that also bring in warm air into polar regions.

You can see how the wind is pushing air into the Arctic that is warmer than 32 degrees Fahrenheit, shown in green in the animation below:

Temperatures rising above the freezing in the Arctic is a crucial threshold. “That’s the point where everything changes,” said Marco Tedesco, a geophysicist at the Lamont-Doherty Earth Observatory. “This is extremely exceptional.”

These higher temperatures start changing the way ice forms, resulting in thinner, less dense sheets. Weather conditions above the melting point of ice also alter how snow accumulates, leading to snowpacks that are more sensitive to heat.

Thinner ice and lighter snow then have knock-on effects for the Arctic weather system as a whole, since heat can more easily flow from the sky to the sea and vice versa. Scientists are still trying to understand how this reverberates throughout the world, but they’re already seeing strong waves that would otherwise be tempered by ice cover battering parts of the Alaskan coast and eroding the coastline.

Some of the biggest effects of the smaller winter ice cap and lighter snowpack will emerge later this year as the summer heat pushes polar ice back even further, amplifying the ongoing effects of rising average temperatures around the world.

“That hastens the slide toward an ice-free Arctic. It’s putting you on a bad footing,” Serreze said.

This is more bad news for the North Pole

We can’t directly attribute the recent heat spell in the Arctic to climate change, but the past few years of record high temperatures and record low sea ice fit the trend of what scientists expect as the average temperatures go up.

Scientists project that heat waves will become more frequent, intense, and longer lasting as average temperatures go up. (And yes, 43 degrees Fahrenheit counts as a heat wave in the Arctic.)

Already, we’re witnessing the fastest decline in Arctic sea ice in at least 1,500 years. And this change isn’t slow and gradual; sea ice has seen a sharp and rapid drop.

We’ve seen similar stark changes in ice on land. Greenland’s ice sheet, which would raise global sea levels by 25 feet if it all melts, has seen portions reach a tipping point where they have suddenly started melting 80 percent faster.

As a result, scientists are bracing for more weird weather around the world that could bake cities, freeze freeways, and dump rain without warning.

“The Arctic keeps throwing us curveballs,” Serreze said.