Atmospheric Forcings or Snow Cover: What’s driving observed trends in snowmelt?

Keywords: snowmelt, Great Lakes, synoptic, climate change
Session Type: Virtual Paper
Day: Saturday
Session Start / End Time: 4/10/2021 08:00 AM (Pacific Time (US & Canada)) - 4/10/2021 09:15 AM (Pacific Time (US & Canada))
Room: Virtual 40

Abstract

Runoff generated by snowmelt plays a critical role in the regional hydrology of the Great Lakes basin, but also presents a physical hazard for local communities during rapid melt events. Such snowmelt events are driven by a combination of sufficiently deep snow packs and the occurrence of suitable atmospheric conditions. In recent decades, the frequency of snowmelt events within the basin has generally decreased, however it remains unclear what is predominantly driving these declines: changing snow cover or atmospheric conditions. Using synoptic classification techniques, here we show atmospheric conditions are becoming more favorable for melt, with warmer temperatures, more southerly winds, and less cloud cover, plus increases in precipitation specifically during instances of rain-on-snow. This is similarly noted during the occurrence of extreme melt events, suggesting the potential for more frequency, extreme, and perhaps earlier melt events. However, despite the presence of more frequent and generally favorable atmospheric conditions for snowmelt over time, snow depth across the basin has widely decreased, and is closely related to ablation frequency. The declines in snow depth appear to be the dominant feature decreasing melt frequency.