(CNN) The Arctic's snow and ice are the planet's air-conditioner, reflecting the sun's energy back into space and keeping temperatures around the North Pole cool.

But a new report shows there are signs that this critical cooling system may be breaking down, and the impacts of what is happening in the Arctic are being felt by people and ecosystems far beyond.

In 2019, average air temperatures in the Arctic were 1.9 degrees Celsius (3.42 degrees Fahrenheit) above normal, the second-hottest recorded since 1900, according to the National Oceanic and Atmospheric Administration's annual Arctic Report Card , published Tuesday.

The high temperatures in 2019 are another sign that the current period of Arctic warming shows no signs of stopping.

Since the mid-1990s, the Arctic has experienced levels of warming that are more than double the global average. And since 2014, every year in the Arctic has been warmer than any year between 1900-2014, the study found.

The authors say these exceptionally high air temperatures are at the root of the other impacts chronicled in the report -- from shrinking sea ice cover and shifts in fish species distributions, to near-record melting on Greenland's ice sheet and permafrost thaw.

For years, climate scientists have paid close attention to the Arctic to understand the effects of human emissions of heat-trapping gases.

The Arctic is a bellwether for the global climate -- seemingly small changes here can have huge consequences, and portend what's to come for the rest of the planet.

"A couple of degrees of warming in Florida is something you may not even notice. But in the Arctic, going from 31 degrees to 33 degrees (Fahrenheit), you're going from ice-skating to swimming in the Arctic Ocean," said Walt Meier, a senior research scientist at the National Snow and Ice Data Center and a co-lead author on the Arctic Report Card's sea ice section.

Sea ice is shrinking. The fish we depend on are searching for colder waters

One of the most significant impacts of a warmer Arctic is the effect the heat is having on the region's sea ice, which continued a pattern of decline in 2019.

Warmer temperatures lead to less ice and snow, which means less sunlight is reflected and more heat is absorbed by the dark water of the open ocean. This warms the ocean further, which continues a vicious cycle that shrinks the sea ice even more.

Sea ice coverage in the Arctic usually reaches its annual minimum in September after the ice melts over the summer months.

This year, the remaining area of ice after the summer melt was tied with 2007 and 2016 for the second-lowest ever recorded. The 13 lowest sea ice extents in the satellite record have now all occurred in the last 13 years.

Sea ice usually freezes again during the cold winter months, but the 2018-2019 winter maximum extent of sea ice coverage was also much smaller than normal, ranking as the seventh-lowest recorded, according to the report.

Fragmented sea ice leaves the Arctic between Greenland and Svalbard, Norway.

There have been other significant changes to the thickness of the sea ice in recent years, which continued in 2019.

As recently as 1985, older and thicker ice made up 33% of the sea ice at the end of winter. But the Arctic's ice has thinned drastically lately. In March 2019, barely more than 1% of the sea ice was thick ice that remained frozen from the previous year.

"We're seeing a continued shift towards a younger, thinner, and less extensive ice cover," Meier said.

The vanishing sea ice has well-documented impacts on animals like polar bears that use it as a platform from which to hunt their prey. But it is also having major impacts on other species too, including humans.

The Bering Sea, which links the northern Pacific Ocean with the Arctic Ocean, provides more than 40% of the US catch of fish and shellfish, and many indigenous communities depend on its waters for food.

The hunters in the village of KIvalina, Alaska, have seen the migration patterns of fish, caribou, seal and whale that they need for the long winter months change due to the warming weather.

The presence of certain kinds of fish in the Bering Sea is dependent on the formation of sea ice there, which cools the waters to make an ideal habitat for its native species.

But the Bering Sea has seen record low sea ice the last two winters and the change is reshaping the entire marine ecosystem, the report says.

Without sea ice to cool the water, fish and other species that prefer warmer waters are pushing into areas outside of their normal range, while cold water species are moving further north into the Arctic.

According to testimony in the report from leaders of indigenous communities, these seismic changes are imperiling the food sources their people rely on.

"In a warming Arctic, access to our subsistence foods is shrinking and becoming more hazardous to hunt and fish," they say in the report.

Greenland's melt is accelerating. That's bad news for coastal cities

Greenland's ice sheet contains enough water to raise global sea levels by more than 24 feet, and the report finds that 2019 was another year of near-record melting,

The ice lost in 2019 rivaled the melting seen in 2012, which set the record for melting on the ice sheet.

The report finds that between 2002 and 2019, enough melt water from Greenland's ice sheet spilled into the ocean to raise global sea levels by an average of 0.7 millimeters each year.

That might not sound like much, but analysis shows that 190 million people currently live below where the high tide line is expected to be in 2100 , so seemingly small amounts of sea level rise can have huge impacts on coastal communities.

Scientists found that melting on Greenland's ice sheet was very near record levels in 2019.

"There is some amount of sea level rise that is now 'baked in'," said Twila Moon, another research scientist at the NSIDC and one of the authors of the Arctic Report Card's Greenland chapter. "However, the actions that we are taking right now are going to make a very, very large difference in how much sea level rise there is in the future."

Another study released Tuesday in the scientific journal Nature brought even more bad news for Greenland and the billions of people living along the world's coasts.

Between 2005 and 2011, Greenland's ice sheet melted at a rate that was five times faster than during the early 1990s . And all told, Greenland's melting tracks closely with the worst-case sea level rise scenarios projected by the UN's Intergovernmental Panel on Climate Change.

At this rate, melting from Greenland's ice sheet alone could raise global sea levels by close to half a foot by 2100.