In a year full of troubling signs that Earth’s climate is rapidly changing, some of the most alarming signals came from the Arctic.

The thawing tundra has become a source of greenhouse gas emissions, instead of locking away carbon. Sea ice levels are near historic lows. Fires are getting worse. Surface air temperatures are near record highs. And, yes, the polar bears are in trouble.

“There’s a lot going on in the Arctic,” said Brendan Rogers, an Arctic scientist at the Woodwell Climate Research Center in Falmouth, Mass. “There’s big changes in the rivers, and with salmon, and big changes in the atmosphere, and with sea ice, and ocean productivity, and the fauna.”

One area of particular concern to Rogers is the increase in wildfires. Fire season is getting longer, the fires are burning bigger and hotter, and more fires are being ignited by lightning strikes.

“The primary reasons are all directly tied to climate change,” he said.

Some fire activity is natural, of course. But Rogers said that, because of climate change, “the fires are happening too quickly, too much; they’re also increasing in severity and intensity.”

Another point of acute concern: Parts of the Arctic that have long stored carbon are now turning into sources of carbon.