Interbasin exchange of hypoxic water in the western basin of Lake Erie

Session: Oxygen Cycling and Hypoxia: Processes, Impacts, and Management

Aidin Jabbari, University of Guelph, [email protected]
Reza Valipour, Environment and Climate Change Canada, [email protected]
Leon Boegman, Queen's University, [email protected]
Yingming Zhao, Ontario Ministry of Natural Resources, [email protected]
Josef Ackerman, University of Guelph, [email protected]

Abstract

Hypoxic conditions (dissolved oxygen [DO] concentrations < 2 mg L-1) due to (1) seasonal warming during calm and warm periods and (2) instantaneous upwelling of cold-hypoxic hypolimnetic water from the central basin have been reported as the main causes of stratification and hypoxia in the western basin of Lake Erie.  We investigated these processes using field measurements at two locations in Pigeon Bay and one location at the northwest of the central basin during a 50-day period in summer of 2018. We recorded an almost continues period of 24 days of hypoxia within 1 m of the bed in the western basin caused by upwelling from the central basin that were followed by strong winds from the south and southwest tilting the thermocline upward in the northwest of the central basin due to Ekman transport.  Upwelling stratification is stronger than seasonal warming and thus reduces the DO flux through the thermocline, which could lead to more severe hypoxia.  Comparisons with historical measurements revealed that upwelling stratification is responsible for > 60% of hypoxia in the study area during the late summer over the past 30 years.  Results will help with the prediction of hypoxia as well as fisheries management.