Have climate change and warmer winters altered freeze-thaw patterns?

Although an increase in the number of freeze-thaw (F/T) events are known to cause increased damage to pavement systems, further research is required to understand the impact of climate change on F/T cycles. This study aimed to determine the frequency of F/T cycles, and hence damage events, at typical air temperature sensor levels, in various layers of pavement, and at critical subgrade locations. In response to global warming, the study considered rigorously computed F/T events rooted in Minnesota climate data between 1901 and 2020. Cooperative Observer Network (COOP) and Modern-Era Retrospective Analysis Version 2.0 (MERRA-2) data were employed to examine subsurface warming conditions. The number of F/T cycles at the air temperature sensor level and individual pavement layers was determined by utilizing historical data from the COOP weather stations and Minnesota Road Test Facility (MnROAD). The evaluation was conducted on both a monthly and yearly basis. Results indicated that starting from 1981, Minnesota winters have become warmer by 0.1 to 1.2 degrees C in the daytime and by 0.3 to 1.5 degrees C during nighttime. The warmer winter weather results in fewer F/T cycles at shallow pavement levels on an annual basis while remaining erratic at deeper sub-pavement locations. The reduction of F/T events at shallower pavement depths was substantial during the late fall and early spring months. While monthly composites of F/T events at air-temperature sensor levels also reflected a decrease in F/T cycles during late fall and spring, the annual frequency of F/T events was randomly distributed.