Unique thermal mixing patterns in Lake Ontario revealed by novel year-round observations of thermal stratification

Limnology and Oceanography
By: , and 

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Abstract

Year-round records of thermal stratification in the Great Lakes are rare, and there are few observations of thermal stratification during winter. In this paper, we analyze temperature data from 13 temperature logger chains and from over 130 benthic acoustic receivers that were deployed across Lake Ontario for 2 yr. The timing and duration of the fall overturn correlate with the local average water depth, and shallow sites (< 50 m depth) overturn up to a month before deep sites (> 100 m depths). Likewise, in spring, the shallow sites warm faster. Lake Ontario has partial ice cover, so wind-driven mixing stirs the water column throughout winter, and inverse thermal stratification is largely absent. The depth-averaged winter water temperatures vary between 0°C and 4°C, with the coldest temperatures (near 0.1°C) found in the shallow Kingston basin and warmest temperatures (near 4°C) at sites near the 244 m deep Rochester Basin. Lake Ontario appears to be a warm monomictic lake, rather than having a dimictic mixing pattern as previously described—there is no sustained ice cover or inverse stratification that inhibits vertical mixing in winter. Winter is a poorly understood season for many aquatic processes, including fish bioenergetics, fish distribution, biochemical processes, invertebrate distribution, and production. Moreover, the lack of knowledge of winter has hampered the use of correct initial conditions for running large lake hydrodynamic models.

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Publication type Article
Publication Subtype Journal Article
Title Unique thermal mixing patterns in Lake Ontario revealed by novel year-round observations of thermal stratification
Series title Limnology and Oceanography
DOI 10.1002/lno.70215
Volume 70
Issue 11
Publication Date September 30, 2025
Year Published 2025
Language English
Publisher Wiley
Contributing office(s) Great Lakes Science Center
Description 16 p.
First page 3401
Last page 3416
Country Canada, United States
Other Geospatial Lake Ontario
Additional publication details