Observations and environmental implications of variability in the vertical turbulent mixing in Lake Simcoe

Chowdhury, Mijanur R., Wells, Mathew G. and Cossu, Remo (2015) Observations and environmental implications of variability in the vertical turbulent mixing in Lake Simcoe. Journal of Great Lakes Research, 41 4: 995-1009. doi:10.1016/j.jglr.2015.07.008


Author Chowdhury, Mijanur R.
Wells, Mathew G.
Cossu, Remo
Title Observations and environmental implications of variability in the vertical turbulent mixing in Lake Simcoe
Journal name Journal of Great Lakes Research   Check publisher's open access policy
ISSN 0380-1330
Publication date 2015-12-01
Year available 2015
Sub-type Article (original research)
DOI 10.1016/j.jglr.2015.07.008
Open Access Status Not Open Access
Volume 41
Issue 4
Start page 995
End page 1009
Total pages 15
Place of publication Philadelphia PA, United States
Publisher Elsevier
Collection year 2016
Language eng
Formatted abstract
A field study was conducted in Lake Simcoe to examine variations in turbulent mixing rates for a 40-day period in late summer of 2011. High sampling frequency records of water currents and temperature profiles were acquired using an acoustic Doppler current profiler (ADCP) and a chain of fast-response temperature loggers respectively. The acquired data were processed to quantify the relative strengths of the stratification in relation to the velocity shear, expressed by the dimensionless gradient Richardson number (Rig). We then used the calculated Rig as a proxy to estimate vertical turbulent eddy diffusivity (Kz) in the stratified water column of the lake. Kz exhibited large spatial and temporal variability with frequent high values in the epilimnion (Kz ~ 10− 5–10− 4 m2 s− 1), and relatively low values in the metalimnion (Kz ~ 10− 7–10− 6 m2 s− 1) and the hypolimnion (Kz ~ 10− 6–10− 5 m2 s− 1). We correlated the Kz variability with the environmental forcing through the Lake number (LN), which expresses the relative strengths of the stratification to the wind forcing. Analysis of the environmental implications of Kz variability suggested that vertical turbulent transport of dissolved oxygen was 10% of the total oxygen depleted in the hypolimnion for the observation period. We concluded that at least some of the observed year-to-year variability of hypolimnetic oxygen depletion could be due to the variation in turbulent transport of dissolved oxygen across the thermocline.
Keyword Dimictic lake
Thermal stratification
Turbulent mixing
Hypoxia
ADCP
The gradient Richardson number
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Civil Engineering Publications
Non HERDC
 
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Created: Thu, 18 Feb 2016, 21:06:40 EST by Jeannette Watson on behalf of School of Civil Engineering