Title | Observation and analysis of shear instability in the Fraser River estuary |
Publication Type | Journal Article |
Year of Publication | 2009 |
Authors | Tedford E.W, Carpenter J.R, Pawlowicz R, Pieters R., Lawrence G.A |
Journal | JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS |
Volume | 114 |
Date Published | NOV 4 |
ISSN | 2169-9275 |
Abstract | We investigate the occurrence of shear instability in the Fraser River estuary. Instabilities observed with an echo sounder are compared with a linear stability analysis based on observed velocity and density profiles. We find that each set of observed instabilities coincides with an unstable mode predicted by the Taylor-Goldstein equation. Each of these instabilities occurs in a region where the gradient Richardson number is less than the critical value of 1/4. Both the Taylor-Goldstein predictions and the echo soundings indicate the instabilities are concentrated either above or below the density interface. This ``one sidedness'' is in contrast to the archetypal Kelvin-Helmholtz instability. Although the dominant source of mixing in the estuary appears to be caused by shear instability, when the tide produces strong near-bed velocities, small-scale overturning due to boundary layer turbulence is apparent throughout the depth. |
DOI | 10.1029/2009JC005313 |