As for the human impact, increased freeze-thaw cycles can impact the integrity of building and road structures leading to potholes and decomposition of building materials such as siding. (Greg Clarke/Flickr Creative Commons)
Connecticut has seen extreme shifts in temperature this winter, which are negatively impacting the Earth’s atmosphere through cyclical freezing and thawing periods. These temperature shifts range from mid-50s degree weather on Jan. 1 in Hartford to a chilling -1 degree Fahrenheit on Jan. 21, according to AccuView Weather.
Periodic cycles of freezing and thawing are natural, but they can have significant impact on our atmosphere and infrastructure in severe cases. Freeze-thaw cycles contribute to erosion through the expansion of frozen water and can increase levels of carbon dioxide (CO2), according to CBS Chicago.
Cristian Schulthess, an associate professor in plant science and landscape architecture at the University of Connecticut, said biological breakdown in the soil is greatly accelerated during periods of warmth.
“The impact of nutrient concentrations is more significant than the impact of environmental temperature. Intuitively, I would expect CO2 emissions to also increase with the freeze thaw cycles,” Schulthess said. “The more bioactive the environment, the more decomposition of soil organic molecules will be observed.”
Schulthess also said an increase in the frequency of freeze-thaw cycles contributes to a greater emission of carbon dioxide, as more microorganisms are active and able to break down organic soil material.
“It turns out that the structure of water in the bulk media is easier to convert into the structure of ice, and hence it is easier to freeze than the structure of water near the solid surface,” Schulthess said. “So as soil freezes, it is freezing toward the solid particles, not from them. There may be several microorganisms that survive the winter freeze in that thin film ‘thawed’ region surrounding each soil particle.”
Erosion can occur when water enters a crevice and freezes. As water freezes, it expands, pushing the surrounding materials and increasing the size of a gap, according to CBS Chicago. This phenomenon is often seen in soil which, Schulthess said, often impacts agriculture.
“Freeze-thawing also impacts soil compaction, which impacts soil aeration, and this in turn impacts soil biochemical reactions, which in turn impacts SOM content and CO2 emissions,” Schulthess said. “Water is attracted to solid surfaces and this causes the water to orient itself in a special way relative to the surface. The next nearest water molecules are also impacted and will tend to follow the orientation set by the first layer of H2O molecules, and so on.”
The way in which water molecules orient themselves is a key contribution to soil aeration, which is essential to crop and root growth, and soil integrity. According to Schulthess, this can have major effects on agricultural processes as well.
“It will soon reach a point where the bulk water orientation is dominating, but the region near the solid surface will have a different average structure,” Schulthess said. “The structure of water is not rigid; it is very short lived; and hence it is a liquid. The effect of this phenomenon is that the water molecules in the bulk liquid have a different freezing point than the water molecules near the solid surfaces.”
Schulthess also brought up how freeze-thaw cycles can also impact the salinity, or the amount of salt, within soil. An increase in salt lowers the freezing point of water. This is the reason much as sidewalks are coated in salt to prevent the accumulation of ice.
“To further complicate things, the unfrozen portion of the soil is becoming saltier and saltier. This is because the salts in the soil liquid phase are not part of the ice phase,” Schulthess said. “The salts remain in the liquid phase and the liquid thus becomes saltier and saltier.”
More salt within soil liquid results in more nutrients for microorganisms, Schulthess said. This is yet another factor that contributes to the emission of carbon dioxide.
“The impact of this is that the liquid phase also becomes more and more difficult to freeze. Salty water has a lower freezing point,” Schulthess said. “The salty thin film region that survives the winter next to each soil particle is thus rich in nutrients, which is a nice bonus for the microorganisms that are able to survive there.”
As for the human impact, increased freeze-thaw cycles can impact the integrity of building and road structures leading to potholes and decomposition of building materials such as siding.
“I would expect fewer loss of nutrients if it is only one cycle per winter season rather than several cycles and soil nutrients impacts soil fertility, which impacts crop yields,” Schulthess said.
Rachel Grella is a campus correspondent for The Daily Campus. She can be reached via email at rachel.grella@uconn.edu.
