Understanding the Hydroclimatic Drivers of Harmful Algal Blooms in the Laurentian Great Lakes Region

Abstract:

Surface water quality is influenced by the changes in the regional hydroclimate and human activities which can cause sensitive coastal regions to deviate from their natural state. In the Great Lakes region, a manifestation of these effects is through the increased frequency, magnitude, and spatial extent of Harmful Algal Blooms (HABs). These HABs are driven by anthropogenic activities (e.g., agricultural and land management practices, wastewater discharge, etc.) and hydroclimatic factors in the form of precipitation patterns and surface runoff. The latter are the underlying driver of HABs and a critical component in forecasting the extent of these blooms in future.

This work focuses on two science questions: 1) Identify the drivers of precipitation seasonal cycle and changes under future climate scenarios; and 2) Explain the effects of cold-season processes and precipitation phase on surface runoff. The aim of this study is to understand the processes involved in the atmospheric moisture and hydrological budgets that drive the surface runoff and can subsequently alter the nutrient loads into the lakes.

Using various reanalysis and CMIP6 datasets to study the atmospheric moisture processes, we found that the future projections suggest a shift in the seasonal cycle of precipitation in the Great Lakes region, with drying in the summer months and wetter winter/spring/early-summer months. This shift in seasonal magnitudes, especially higher precipitation in the colder months, can alter the precipitation phase that will likely affect runoff quantities. To further investigate the impacts of seasonal precipitation changes on runoff, we conduct high-resolution WRF (Weather Research and Forecasting) model simulations of precipitation phase in the Lake Erie basin that will provide forcing for the WRF-Hydro model to conduct surface hydrology assessments and quantify variations in runoff quantities.