Evaluating the Relationship Between Extratropical Cyclone Tracks and Teleconnection Patterns to Improve Laurentian Great Lakes Water Level Modeling

The Laurentian Great Lakes (hereafter Great Lakes) serve an important role in regional commerce, transportation, hydropower, and recreation. In addition, these vast bodies of water provide a vital trade route for transporting goods from the United States and Canada to the rest of the world. Changes in water levels within the Great Lakes can have a significant impact on these economic drivers, including the cost and time of transporting goods, changes in required coastal infrastructure, and ecosystem changes. Accurately predicting Great Lakes water level changes is crucial to adapting accordingly to the inevitable impacts.

Lake level changes are controlled by a combination of the component net basin supply (CNBS; basin-wide precipitation, lateral runoff, and over-lake evaporation) and water exchange between lakes. The individual quantities of the CNBS are influenced by various factors, ranging from regional and synoptic weather patterns to hemispheric and planetary-scale teleconnection circulations. Understanding the role of these larger-scale patterns in relation to the behavior and influence of each CNBS mechanism is paramount for effective water management and accurate lake water level predictions.

For this study we examine the seasonal role of extratropical cyclones (ETCs) on the CNBS of the Great Lakes. ETCs can enhance over-lake precipitation and regional runoff, resulting in increased water supply and water levels on meteorological time scales. ETCs can also impact over-lake evaporation through changes in over-water atmospheric lapse rates and cloud-cover impacts on solar insolation. However, the degree to which CNBS components change on a seasonal to annual timescales varies by ETC frequency, track, and origin. This longer-term evolution of ETC impacts is partially controlled by the planetary teleconnection patterns in place or forecasted to be dominant in the future.

A valuable tool that can be used to better understand CNBS is the Large Lake Statistical Water Balance Model (L2SWBM; Gronewold et al., 2016), which applies probability distributions to evaporation, runoff, and precipitation observations and produces estimates with uncertainty for resolving the Great Lakes water cycle (Fry et al., 2022). We use 1950-2019 L2SWBM monthly output with ERA5 reanalysis data to examine the seasonal impacts of ETCs on CNBS and to better understand ETC mechanisms responsible for lake level changes. We then bin ETCs by teleconnection phase and strength to investigate how North American storm tracks respond to planetary atmospheric and oceanic conditions, and how these changes could affect Great Lakes CNBS. ETCs are detected in 6-hourly ERA5 data using the TempestExtremes v2.1 feature detection suite (Ullrich et al., 2021). We then compare regional ETC presence to L2SWBM water level changes for each season using compositing techniques. The goal of this project is to develop an enhanced comprehension of direct and remote influences on Great Lakes’ water supply, allowing for the creation of the requisite datasets for the next-generation Great Lakes water level forecasting system, as part of the Great Lakes Environmental Research Laboratories’ Bipartisan Infrastructure Law: Subseasonal to Annual (BIL-SA) project.