Thawing Permafrost Is Unlikely To Increase Global Warming, Scientists Find – Forbes
Fall colors in tundra, in Tombstone national park. Yukon, Canada
As Earth continues to warm, scientists were wary about the impact melting permafrost would have in furthering greenhouse gas warming. Recent research suggests that melting permafrost may not have a significant impact on increasing temperatures.
The primary concern was associated with methane gas release into the atmosphere, which is a much more potent heat-trapping gas than carbon dioxide.
The research study focused on two types of permafrost, frozen soil and frozen methane hydrates in the soil underneath the world’s oceans.
Permafrost on land is predominantly found in Siberia, Alaska, and Northern Canada. As plants, algae and animals die in these regions significant amounts of the carbon are not decomposed but buried in frozen soil. This “locks away” this organic matter from the global carbon cycle.
As temperatures warm the soil begins to melt, introducing liquid water and oxygen to the organic matter and thus allowing bacteria to break it down and potentially release methane into the atmosphere.
Methane hydrates, the other main concern for permafrost melting, are a combination of water ice and methane trapped in frozen ocean sediment below the ocean floor. Similar to permafrost on land, as oceans begin to warm these hydrates will begin to melt and release both water and methane.
In both scenarios, the concern is that a warming planet will cause a sudden release of significant amounts of methane into the atmosphere, thus causing positive feedback and warming the planet more.
Louis Sass, a Physical Scientist with the United States Geological Survey, uses tape to measure the … [+]
Recent research, published in the journal Science, looked at small trapped gas bubbles in ice cores to see what the atmosphere looked like on Earth for the past 15,000 years.
By analyzing the gas bubbles, which were sequentially trapped through time and represent past atmospheric conditions, the team believes methane release from permafrost did not play a significant role in warming during past warming events.
The scenario they used was from the last glacial period to modern times, analyzing how permafrost played an impact on a warming planet.
The team found that signatures of methane gas were small during these past warming periods and that methane release from permafrost likely did not cause a large warming event.
In the case of land permafrost, in most scenarios the bacteria decomposed the organic matter through organic respiration, releasing carbon dioxide as opposed to methane. While the carbon dioxide released does add to warming, as we stated earlier, each molecule of CO2 is less potent than a molecule of methane (CH4).
When looking at methane hydrates in the ocean sediment, the team found that a significant amount of the methane released never makes it to the ocean surface. It simply dissolves into the ocean water as trapped gas or is oxidized by microbes in the ocean.
While this is good news that permafrost appears to play a smaller role in potential warming, that doesn’t mean we shouldn’t be concerned with methane as a greenhouse gas.
Vasilii Petrenko, an earth science professor and co-author of the paper clarifies, “our data shows we don’t need to be as concerned about large methane releases from large carbon reservoirs in response to future warming; we should be more concerned about methane released from human activities.”