Towards Improved Understanding of Extreme Snow Melt Runoff Events: a Case Study of the Chesapeake Basin

Snow cover and its seasonal ablation is an important contributor to crucial hydrological variable such as streamflow, soil moisture, and groundwater supplies. Seasonal variations in the frequency and magnitude of large ablation events are important as they can lead to severe environmental and societal consequences for any region with snow present in its annual cycle. Such consequences may manifest themselves as: snowmelt-induced floods, lack of streamflow in snowmelt fed rivers, and transport of pollutants or excess nutrients in rapid snowmelt events, to name just a few. Little research has been conducted on understanding the connection between the frequency and magnitude of ablation events on a basin scale and the role of global-scale atmospheric and oceanic forcings in their variation. Moreover, the pathways that link global-scale forcings to basin-scale snow hydrology are poorly understood as is the manifestation of snow-induced streamflow variability in future climate scenarios.

Motivated by recent trends in Northern Hemisphere spring snow cover, this study explore the potential for more intense, earlier snowmelts, and the impact of such events of the hydroclimatology of the Chesapeake Basin, a region encompassing some 165,759 kmē. Gridded daily snow depth data at 1° X 1° spatial resolution from 1950-2009 was used to build a climatology of extreme ablation events for the Chesapeake, identifying events using both daily and multi-day depth change values in conjunction with streamflow discharge rates. Atmospheric forcings leading up to and during identified events were further classified by air mass and synoptic types, with the goal of identifying pathways by which global-scale anomalies can influence this major basin.