Over the years, Alaska receives increased precipitation, a fact that will lead to its permafrost thaw in the future.
A new study, recently published in Nature's npj Climate and Atmospheric Science Journal, focuses on how rainfalls affect the permafrost of Alaska, a correlation that has not been thoroughly studied until today.
Permafrost refers to any soil material that lies beneath the Earth's surface and its temperature is less than 0°C, thus it is completely frozen. Permafrost ground is common in regions with low temperatures such as mountainous areas and those near the poles of the planet.
Frozen grounds cover a large proportion of the Earth's surface (25% of the Northern Hemisphere is occupied by frozen ground). Interestingly, some of the regions which have permafrost are not covered by snow.
Alaska is currently experiencing extreme weather phenomena which include both increased temperatures, wildfires and heavy rainfalls. In fact, during the past 5 years, Alaska has received a century-record amount of precipitation. These extreme weather alterations are caused by climate change and are responsible for a phenomenon known as Polar Amplification which leads to larger temperature changes near the poles than the Earth's average temperature increase.
According to Prof. Merritt Turetsky, co-author of the study and Director of Colorado University Boulder’s Institute of Arctic and Alpine Research, those changes occur at a very high rate and could potentially affect the ecosystems in Alaska. “These changes are not occurring gradually over decades or lifetimes; we are watching them occur over mere months to years," Prof. Turetsky stated.
Over the aforementioned 5-year period, the team conducted in-situ investigations and took 2750 measurements of the permafrost subsidence by the end of the summer period. During the years that the region received the largest amount of precipitation, the permafrost retreat was higher. Moreover, after the wettest summer (2014), permafrost retreated and did not bounce back to its initial levels in the winter, a fact that proves that meltdown is permanent.
While Polar Amplification is a phenomenon adequately studied, its impact on the planet's permafrost has not been understood yet. Permafrost meltdown is a critical issue as the frozen grounds contain huge amounts of carbon dioxide which would be released into the atmosphere intensifying the greenhouse effect on Earth. Moreover, many infrastructure projects are founded or supported by permafrost and could be damaged or destroyed in case it is removed.
The researchers suggest that the permafrost thaw is also dependent on the terrain. For example, forests with thick moss layers were highly resistant to this phenomenon while tussock tundra was the least resistant terrain possibly because water from rainfalls accumulates on the flat ground and impacts permafrost for a longer duration.
Click the video below to see how a measurement of the permafrost's level is conducted.
Source: CU Boulder
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