NBC News reports:

The Arctic just experienced its second-hottest year on record. And concerningly, the region’s tundra has transitioned from being a sink for carbon to a source of emissions as permafrost melts to release methane.

That will only amplify the amount of heat-trapping gases that enter the atmosphere, paving the way for further warming.

The findings, shared Tuesday in the National Oceanic and Atmospheric Administration’s Arctic report card, show how climate change is scrambling ecosystems and shape-shifting the landscape in the part of the planet where global warming is most intense.

Considered a bellwether region for the effects of climate change, the Arctic is heating up far faster than places at lower altitudes — two to four times as quickly, depending on the baselines scientists use for comparison and which geography they include in assessments. The last nine years in the Arctic have all had the highest average temperatures recorded since 1900.

That dynamic is the result of a phenomenon called Arctic amplification. As the Arctic loses snow cover and sea ice, more dark-colored ocean water and rock emerge. Those dark surfaces reflect less radiation back to space, absorbing heat, instead. In addition, patterns of circulation in the oceans and the atmosphere are increasingly transporting heat toward the Earth’s poles.

Together, that means the Arctic is a fundamentally different place from what it was just 10 years ago, said the lead editor of the new NOAA report, Twila Moon, deputy lead scientist and science communication liaison at the National Snow and Ice Data Center. [Continue reading…]