Satellite data shows acceleration of Arctic carbon cycle

Region is behaving more like a boreal forest than a tundra.
By Laurel Kornfeld | Aug 08, 2018
Satellite data collected under NASA's Arctic Boreal Vulnerability Experiment (ABoVE) confirms the Arctic carbon cycle is speeding up due to warming temperatures, causing the region to act more like a North American boreal forest than like icy tundra.

Boreal forests are those found in regions south of the Arctic, specifically cold, temperate regions.

A NASA research team analyzed over 40 years of carbon dioxide surface measurements acquired by the National Oceanic and Atmospheric Administration's (NOAA) observatory in Barrow, Alaska, using a standard computer model geared toward ecosystem carbon balance in a study to determine the rate at which carbon is moving into and out of Alaska's North Slope.

While computer models used in earlier studies indicated an acceleration in the region's carbon cycle, satellite data, along with information collected from the area's air and surface, show that acceleration to be greater than any of the models predicted.

Carbon in the North Slope's tundra regions now spends 13 percent less time trapped in frozen soil than it did four decades ago, the researchers determined.

"Warming temperatures mean that essentially we have one ecosystem--the tundra--developing some of the characteristics of a different ecosystem--a boreal forest," said Anthony Bloom of NASA's Jet Propulsion Laboratory (JPL) in California. "While various factors regulate how fast this transformation will continue to occur, studies using Landsat and MODIS satellite imagery with field measurements over the past decades have observed a northward migration of shrubs and trees."

Landsat is a joint program between NASA and the United States Geological Survey (USGS) of Earth-observing satellites that provide the longest continuous space-based Earth observations. The Moderate Resolution Imaging Spectroradiometer (MODIS) is a satellite that observes every point on Earth in discrete spectral bands every one to two days.

The Arctic carbon cycle involves the release of carbon dioxide during Arctic summers, when warmer temperatures melt the top layers of permafrost, allowing microbes to break down organic matter that had been frozen in colder weather. This triggers plant growth, with plants removing the carbon dioxide as they conduct photosynthesis.

Overall warmer temperatures mean the carbon dioxide spends less time frozen in the soil and more time in the atmosphere, a phenomenon that could have global consequences.

"The balance between these two dynamics will determine whether Arctic ecosystems will ultimately remove or add atmospheric carbon dioxide in the future climate. Our study finds the latter is more likely. We anticipate that residence time of Arctic carbon will lead to faster and more pronounced seasonal and long-term changes in global atmospheric carbon dioxide," said former JPL researcher Sujong Jeong of Seoul National University.

A paper on the study has been published in the journal Science Advances.

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