Characterizing the Impacts of Atmospheric Blocking on Great Lakes' Regional Hydroclimate

Blocking anticyclones (stationary regions of anomalously high pressure) have been identified as major contributors to moisture transport and enhanced precipitation in high latitude regions, but little focus has been given to their effects on Great Lakes’ regional hydroclimate. Blocks are characterized by highly anomalous middle to upper-tropospheric easterlies, which effectively reroute prevailing winds meridionally. Due to their slow-moving, persistent nature, the geopotential height gradient on the edge of the anticyclones can facilitate the transport of deep moisture plumes over long distances. In this study, we investigate the influence of blocking on extreme moisture transport in the Great Lakes Region to better understand impacts on the water budget components, such as evaporation, precipitation, and basin-wide runoff. The Great Lakes are the largest freshwater lake system in the world, containing over 20% of the earth’s freshwater and 30 million people between the United States and Canada. We identify and catalog blocking events and develop an eastern United States and western Atlantic climatology using ERA5 reanalysis data products from 1979-2023 to investigate blocking impacts in the Great Lakes Region. Blocks are detected using the 500 hPa geopotential height data using an identification algorithm based on Masato et al. (2013). We then quantify moisture transport associated with blocks using the ERA5 integrated vapor transport (IVT). To develop a better understanding of the impacts of blocking and their associated moisture transport in the Great Lakes Region, we investigate blocking size and persistence. This assessment will give insight into the associated physical mechanisms responsible for temperature and moisture changes in the Great Lakes Region and how the blocking climatology could change.