By Carola F. Berger, PhD, CT
The Science & Technology Division was very fortunate to have Dr. Nic Jelinski, assistant professor of soil science in the Department of Soil, Water, and Climate at the University of Minnesota, as the Division Distinguished Speaker at ATA62. Mery Molenaar already summarized the first of his two very engaging presentations. Here, I review the second presentation, titled “Permafrost-Affected Soils in Alaska: Distribution, Comparative Morphology, and Change.”
Let’s start with some terminology to make sure we are all on the same page. Dr. Jelinski defined “soil” as the unconsolidated mineral or organic material on the surface of the Earth that has been subject to and shows the effects of alterations by parent material, climate, organisms (flora and fauna), topography, and time. It is composed of a mineral, inorganic, solid component; an organic solid component; and a pore space component that’s usually filled with air or water, or both. Frozen soil contains both liquid and solid (frozen) phases of water. This makes water in soils a very complex, dynamic system that does not entirely freeze uniformly at 0 degrees Celsius, due to various chemical admixtures. As a result, some water remains in liquid form even in soils that are below the freezing point.
“Permafrost” is defined as any material that remains at or below 0 Celsius for at least two consecutive years. So, permafrost is a thermal state, not a type of material and isn’t necessarily formed of ice entirely, as it can also contain components in liquid and gaseous states. Generally, there is an active, non-permafrost layer of soil that thaws and refreezes. This sits on top of the permafrost table marking the upper limit of the permafrost, where the maximum temperature is below 0 degrees Celsius. Below that is a more or less thick layer of permafrost, the bottom base of which is also heated above 0 Celsius by geothermal energy.
The Importance of Permafrost
In Northern Alaska, the permafrost distribution is continuous. Some places contain permafrost that has been present since the last ice age, as determined by carbon dating. Between the Northern and Southern mountain ranges in Alaska, however, the permafrost distribution is discontinuous and depends on environmental conditions such as snow and vegetation, which are good insulators, and wildfires, which heat up the soil.
As Dr. Jelinski explained, permafrost is extremely important because permafrost contains much more carbon than is currently in Earth’s atmosphere. This disproportionate amount of carbon enclosed in permafrost—accounting for about 30-40% of the total amount of carbon in Earth’s soils—is due to the cold temperatures. The cold temperatures inhibit microbial decomposition and keep the carbon from escaping into the atmosphere. Suffice it to say that it would not be a good thing if these carbon stocks were to be released into the atmosphere, which would happen if portions of the permafrost begin to thaw.
Unfortunately, that is exactly what is happening right now. Several decades of study show that arctic permafrost regions are currently experiencing significant climatic change, including warming temperature and increased snowfall. These factors increase permafrost temperatures and, in some cases, lead to permafrost thaw. This in turn leads to thermokarst, where the ground collapses and leaves giant sinkholes. Dr. Jelinski showed some dramatic pictures of entire settlements being swallowed by these craters. Aside from the obvious giant holes in the ground, this process also has an invisible effect: increased release of methane and other carbon greenhouse gases into the atmosphere, which in turn contributes to the warming process. As mentioned above, permafrost contains a disproportionately large amount of carbon, which is why accelerated permafrost thawing is not a good thing.
In summary, aside from their unique beauty, permafrost-affected soils and landscapes play a globally important role in Earth’s climate. The study and preservation of these fragile permafrost ecosystems are therefore of utmost importance. I would like to thank Dr. Jelinski for explaining the global significance of permafrost, a fact that I, at least, was not aware of before his enlightening and wonderfully engaging presentation. Who knew that dirt (soil) could be so exciting and important?