Climate change is speeding up the Arctic’s carbon cycle faster than previously believed, according to 40 years of data compiled from NASA’s Arctic Boreal Vulnerability Experiment (ABoVE). If these rates continue, the North Slope landscape could change to a warmer, more temperate climate found throughout much of North America.
"Warming temperatures mean that essentially we have one ecosystem – the tundra – developing some of the characteristics of a different ecosystem – a boreal forest," said study co-author Anthony Bloom of NASA's Jet Propulsion Laboratory in a statement.
According to research published in Science Advances, Alaska’s North Slope tundra spends 13 percent less time locked in frozen soil than 40 years ago.
Rising global temperatures thaw the uppermost layers of permafrost – a thick layer of soil that remains frozen throughout most of the year. Permafrost holds large stores of organic carbon that have been locked away for thousands of years. When permafrost thaws, so do the organic matter contained in it, such as ancient plants and animals. As the National Snow & Ice Data Center explains, it’s akin to taking a bag of frozen broccoli out of the freezer and putting it into the refrigerator. Eventually, the vegetables will begin to decay and break down.
Microbes found in permafrost break down previously frozen organic matter and release carbon dioxide as waste into the atmosphere. Typically, plant growth during the warmer months removes this waste from the atmosphere by way of photosynthesis. The Arctic carbon cycle is a delicate balance of carbon being released into and removed from the atmosphere, and is skewed as warmer temperatures increasingly thaw the frozen ground at rates that photosynthesis can’t keep up with.
Tundra covers almost 20 percent of the Earth’s surface, and globally it has been thawing at deeper levels for longer periods of time. In parts of Canada, methane gas released from the frozen soils has been dated to more than 2,000 years old. A number of studies suggest that ancient carbon is emerging from Arctic soils, lakes, and rivers at rates faster than previously believed.
The Arctic has long been called the “canary in the coal mine” when it comes to climate change because it is warming at twice the rate as the rest of the world. Currently, the Arctic is a carbon sink because it holds a lot of the world’s carbon in its frozen ground. However, if this trend continues and transitions the Arctic to a carbon source, releasing more carbon than it absorbs, researchers say it could start a cycle that leads to further increased global warming and have implications beyond Alaska.
Researchers say they have measured a northward migration of shrubs and trees over the past decades, indicating that Alaska’s North Slope is transitioning to a boreal, or taiga, forest characterized by warmer temperatures, more precipitation, a greater presence of trees, and the northward migration of animals like moose and deer – who would compete with the Tundra’s reindeer.