Declining North American snow cover ablation frequency

Abstract

At a continental scale, trends in aggregate ablation frequency inform changes in snow cover extent, however the variability and trends in the frequency and magnitude of snow ablation events at regional scales are less well understood. Determining such variability is critical in describing regional hydroclimate, where snow ablation can influence streamflow, soil moisture and groundwater supplies. This study uses a gridded dataset of United States and Canadian snow ablation events derived from 1960 to 2009 surface observations to examine spatial and temporal variations of snow ablation frequency. Here, we show a relatively narrow band of peak ablation frequency seasonally advances and recedes over North America, forced by variations in snow depth and meteorological conditions suitable for ablation. Particularly in more moist regions away from the continent's interior, hydrologically relevant ablation events of at least 10.0 cm occur on an approximately yearly basis. Collectively, ablation events became significantly less frequent with time, where events specifically in the Appalachians and in Great Lakes regions declined by as much as 75% over the 50‐year period. Decreases in ablation frequency across the study region are primarily driven by significant decreases in snow cover, inhibiting the potential for ablation to occur due to a lack of sufficiently deep snowpacks. These results point to important snow cover related changes in the hydrologic cycle in a warming climate and highlight specific areas of interest where more localized analysis of ablation trends and forcing mechanisms would be appropriate.

Ohio River basin snow ablation and the role of rain‐on‐snow

“…The southwest‐to‐northeast increasing gradient of both snow ablation and rain‐on‐snow ablation event frequency observed here is similar to that observed by other studies in the literature that used different approaches (Jeong & Sushama, 2018; Li et al, 2019; Suriano, 2022; Suriano et al, 2021; Wachowicz et al, 2020; among others). For instance, Wachowicz et al (2020) evaluated rain‐on‐snow event frequency seasonally for the eastern United States, inclusive of the ORB, using a 1° gridded snow depth product.…”

“…Prior research has suggested there is evidence U.S. snowfall totals have decreased, and will continue to decrease, with time despite stationary or increasing trends in total precipitation, as less precipitation occurs as snowfall (Notaro et al, 2014; among others). This may yield mixed rain‐on‐snow frequency signals, as less snowfall would result in a thinner snowpack that could be completed ablated more quickly, thus the potential for fewer rain‐on‐snow events once the snowpack is exhausted (Suriano et al, 2021). This aligns with research that suggests snow cover and snow mass has decreased across North America over time (Mudryk et al, 2020).…”