Calculating Lateral Frost Front Penetration in a Rapidly Retreating Cliff of Fine Sediments

Abstract

An adapted version of the Stefan equation (CLIFFSE) was tested to predict lateral progression of the frost front into cohesive sediments that form coastal cliffs along the north shore of the maritime estuary and gulf of the St Lawrence River (Quebec, Canada). The equation was adapted to accommodate the influence of cliff erosion on lateral penetration of freezing and thawing into vertical cliff faces. As the cliff erodes, freezing and thawing are initiated from the newly revealed surface. Frost progression and erosion were measured with an automated thermal erosion pin system. Measured observations agreed with predictions from the adapted equation (78 to 99% of the variability explained). Erosion associated with thawing front progression during winter warm spells led to a relative reduction in the frost front depth. Subsequently, progression of the frost front into the cliff contributed to an additional 50 cm of sediment freezing and erosion by the end of the cold season, which was not predicted by the original Stefan equation. Our findings support the hypothesis that multiple warm spells influence the amount of lateral penetration of the frost front in vertical cliffs.

Long-Term Evolution and Monitoring at High Temporal Resolution of a Rapidly Retreating Cliff in a Cold Temperate Climate Affected by Cryogenic Processes, North Shore of the St. Lawrence Gulf, Quebec (Canada)

“…As a result, the frequency of th events number reached a maximum in early spring and lead to a rapid cliff retreat wit the occurrence of numerous processes (Figure 13). As Boucher-Brossard et al [52] hav shown on the north shore of the St. Lawrence, the maximum annual depth reached by th frost wave can also be increased by winter warm-spell events. They cause the retreat o the silt-clay surface of the cliff, which instantly reduces the distance between the cliff su face and the frost front, and thus allowing the frost wave to continue its progression a depth.…”

“…Early spring (Spring A) begins when the prevailing maximal air temperatures are positive (defined as the cumulative sum of maximal daily temperature of the subsequent deviation from the 0 • C threshold remaining positive). Late spring (Spring B) begins when mean temperatures exceed 0 • C. Following the above characterization, frost action during fall is typically superficial, and during winter, frost typically penetrates the sediment [52,74,75].…”

“…Despite the progress made in the knowledge of the hydroclimatic forcing involved in cliff retreat, very few studies have so far attempted to quantify the relative contribution of different erosion processes to cliff retreat, particularly in cold regions [36]. In cold temperate regions, some erosion processes such as thermoabrasion, which are expected to intensify with the reduction of the ice cover, have not been fully addressed, but have the potential to occur when the frost is active and in the absence of an ice-foot [52]. This gap in the quantification of geomorphological processes is, however, an obstacle towards accurately quantifying environmental drivers of cliff erosion prior to modeling of the coastal system in the context of climate change.…”

Measured and predicted freeze-thaw days frequencies in climate change conditions in central Poland

“…It causes frost-vulnerable silt and clay sediments on vertical or nearly vertical cliff faces to exfoliate and fall off exposing another layer of sediments to frost processes. Consequently, the frost front progresses into the sediments and the rate of the cliff retreat increases ( Bernatchez, Jolivet & Corriveau, 2011 ; Day et al, 2013 ; Boucher-Brossard et al, 2017 ). This process can amount to up to 20–90% of the total annual lake or river cliff retreat being the joint effect of wave erosion and other subaerial geomorphological processes e.g .…”

“…Repeated cycles of freeze-thaw and dehydration create a five to 10 mm-thick mechanically weathered surface layer on the face of the cliff which will be removed or will fall off. Consequently, successive layers of sediments become exposed and subjected to freeze-thaw activity leading to the progression of a frost front into cliff sediments and an increase in the cliff retreat ( Bernatchez, Jolivet & Corriveau, 2011 ; Day et al, 2013 ; Boucher-Brossard et al, 2017 ). Freeze-thaw cycles can substantially decrease erosional resistance of a shore ( Lawler, 1993 ; Gatto, 1995 ; Wynn, Henderson & Vaughan, 2008 ; Pizzuto, 2009 ).…”