A 21st century shift in the mechanisms of the early-winter United States snowfall variability

Abstract

Snowfall is a critical element of natural disasters to the United States (US) with strong climatic and socioeconomic influences. Meanwhile, snowfall acts as a driving force to the US water supplies for agriculture, drinking water and hydropower. However, so far, what factors influence the US snowfall variations and how these factors change under global warming remain unclear. Here, we found that large-scale influences of the early-winter US snowfall experienced a shift from the Pacific to the Atlantic side around 2000, through observational analysis and climate model simulations. The Pacific/North American pattern was identified as a dominant driver of the early-winter US snowfall before 2000, but its impact became much weaker in the 21st century as its associated western North American cell shifted northward away from the US. Instead, the tropical and subpolar North Atlantic surface temperature has been influencing the early-winter US snowfall variations via teleconnections after 2000. This changed influence of US snowfall around 2000 is demonstrated to be related to the observed global warming pattern since the 1950s. Our study provides new perspectives in understanding large-scale snowfall pattern and variability and its connection to the global warming pattern.