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Mixing processes from CTD profiles using a lake-specific equation of state : Quesnel Lake James, Christina

Abstract

Quesnel Lake, is a deep (511m maximum depth) fjord-type lake in northeast British Columbia, Canada. Mixing processes in the lake exchange deep-water with surface water and contribute to the renewal of surface-water nutrients and oxygenated deep-water. These processes are of great consequence to the lake's trophic dynamics and understanding them will enable better management of the large salmon resources in Quesnel Lake. To better understand large-scale convective processes, a lake-specific equation of state was developed. Water samples were collected at locations around Quesnel Lake and analysed for ionic and non-ionic composition as well as other quantities that are integral to determining the lake's equation of state including pH, alkalinity and specific conductance. A relationship was developed to find lake water salinity from CTD data. Salinity was in turn related to density using a modified form of a general limnological equation of state. The equation of state developed for Quesnel Lake gives densities accurate to ± 0.0018kg/m³ whereas the general equation of state (based on seawater composition) is only accurate to ± 0.0158kg/m³ for Quesnel Lake water samples. The lake-specific equation of state was used to identify gravitational instability in density profiles estimated from CTD data. In order to compare water parcel density within a profile, the hydrostatic pressure effect must be removed. The three quantities that are used for this purpose, potential density, quasi-density and standard density, were compared. Quasi-density was found to be most appropriate for Quesnel Lake's deep water which is near the temperature of maximum density. Quesnel lake water column stability was quantified using the Brunt-Vaisala frequency calculated using quasi-density.

Item Metadata

Title
Mixing processes from CTD profiles using a lake-specific equation of state : Quesnel Lake
Creator
James, Christina
Publisher
University of British Columbia
Date Issued
2004
Description
Quesnel Lake, is a deep (511m maximum depth) fjord-type lake in northeast British Columbia, Canada. Mixing processes in the lake exchange deep-water with surface water and contribute to the renewal of surface-water nutrients and oxygenated deep-water. These processes are of great consequence to the lake's trophic dynamics and understanding them will enable better management of the large salmon resources in Quesnel Lake. To better understand large-scale convective processes, a lake-specific equation of state was developed. Water samples were collected at locations around Quesnel Lake and analysed for ionic and non-ionic composition as well as other quantities that are integral to determining the lake's equation of state including pH, alkalinity and specific conductance. A relationship was developed to find lake water salinity from CTD data. Salinity was in turn related to density using a modified form of a general limnological equation of state. The equation of state developed for Quesnel Lake gives densities accurate to ± 0.0018kg/m³ whereas the general equation of state (based on seawater composition) is only accurate to ± 0.0158kg/m³ for Quesnel Lake water samples. The lake-specific equation of state was used to identify gravitational instability in density profiles estimated from CTD data. In order to compare water parcel density within a profile, the hydrostatic pressure effect must be removed. The three quantities that are used for this purpose, potential density, quasi-density and standard density, were compared. Quasi-density was found to be most appropriate for Quesnel Lake's deep water which is near the temperature of maximum density. Quesnel lake water column stability was quantified using the Brunt-Vaisala frequency calculated using quasi-density.
Extent
4965283 bytes
Genre
Thesis/Dissertation
Type
Text
File Format
application/pdf
Language
eng
Date Available
2009-12-03
Provider
Vancouver : University of British Columbia Library
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
DOI
10.14288/1.0063438
URI
http://hdl.handle.net/2429/16247
Degree
Master of Applied Science - MASc
Program
Civil Engineering
Affiliation
Applied Science, Faculty of; Civil Engineering, Department of
Degree Grantor
University of British Columbia
Graduation Date
2005-05
Campus
UBCV
Scholarly Level
Graduate
Aggregated Source Repository
DSpace

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For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.