Ventilation and dissolved oxygen cycle in Lake Superior: Insights from a numerical model

Abstract

Ventilation and dissolved oxygen in Lake Superior are key factors that determine the fate of various natural and anthropogenic inputs to the lake. We employ an idealized age tracer and biogeochemical tracers in a realistically configured numerical model of Lake Superior to characterize its ventilation and dissolved O2 cycle. Our results indicate that Lake Superior is preferentially ventilated over rough bathymetry and that spring overturning following a very cold winter does not completely ventilate the lake interior. While this is unexpected for a dimictic lake, no part of the lake remains isolated from the atmosphere for more than 300 days. Our results also show that Lake Superior's oxygen cycle is dominated by solubility changes; as a result, the expected relationship between biological consumption of dissolved O2 and ventilation age does not manifest. Key Points: Lake Superior is preferentially ventilated over rough bathymetry Overturning following an icy winter does not completely ventilate the lake Dissolved oxygen signal is dominated by physical processes