Soil frost depth

The new measuring system used by a University of New Hampshire research team builds on one of the oldest and most common methods for measuring soil frost depth, the Gandahl frost tube used since the 1950s, pictured here.

The frost heaves that turn New England roads and their drivers into a bumpy mess are one of many consequences of the seasonal soil freeze-and-thaw cycle that affects about half of the northern hemisphere.

“It can destabilize roads and building, cause flooding by enhancing overland flow, and can impact the health of plants — including perennial crops — as well as forest tree species by damaging root systems,” said Alexandra Contosta, research assistant professor with the Institute for the Study of Earth, Oceans and Space, and a researcher with the NH Agricultural Experiment Station.

Yet there is a surprising lack of soil frost research that assesses the timing and extent of frozen soil and its impacts, according to a UNH news release.

Contosta is the lead scientist within a team of researchers at the University of New Hampshire who received a $1.2 million grant to remedy this gap in knowledge.

Scientists aim to answer two questions: how does soil frost vary over space and time, and how do changing soil frost conditions affect ecosystem processes such as soil carbon and nutrient retention?

The seasonal soil freeze and thaw also plays a critical role in the control of nutrient and carbon cycles in temperate ecosystems and affects permafrost, agroecosystems, urban ecosystems and the interface between people, buildings, and roads, the news release said.

A future combination of rapidly warming winters punctuated by extreme cold snaps suggests that freeze and thaw events are likely to increase in mid- to high-latitude regions, including New England, UNH researchers said.

The interdisciplinary team of ecologists, hydrologists, engineers and climate scientists working on the grant will develop and test new systems to understand the variation of soil frost across the landscape.

To do so, they will develop, test and deploy wireless, in-ground sensors and a ground-penetrating radar system for continuous measurements of soil frost. They will use the measurements to understand how changing winter conditions affect soil frost across the landscape and will assess how ecosystems respond to the depth of soil that’s frozen during the winter.

“Together, these new methods will enable more frequent measurements over broader spatial areas, which will provide important insights into soil freezing and its consequences on human and natural systems,” Contosta said.

Decreases in the depth and duration of the snowpack result in an overall reduction in the insulating power of snow and make soils more vulnerable to soil frost, according to UNH researchers.

“Our fully automated, wireless in-ground soil frost sensors and an unmanned aerial system ground penetrating radar technology will advance a fundamental understanding of how rapidly changing winters will impact soil microclimate. This understanding is essential to inform cold season hydrological, agricultural, and ecological processes,” Contosta said.

In addition to Contosta, the UNH scientific team includes climate scientist Elizabeth Burakowski; Experiment Station researcher and microbial ecologist Serita Frey; water resources engineer and surface water hydrologist Jennifer Jacobs; and electrical and computer engineer Shaad Mahmud. John Campbell, research ecologist with the U.S. Forest Service Northern Research Station, also is a collaborator.