Stability characteristics of deep-water replacement in the Strait of Georgia

It has been suggested that low-frequency current fluctuations in the southern Strait of Georgia are the result of baroclinic instability. However, data extracted from cyclesonde and fixed current meter moorings suggest that the conditions for baroclinic instability are highly variable in space and time. It has been recently discovered that there are summertime bottom-intensified gravity currents with fortnightly and monthly periods associated with the introduction of salty waters from the Juan de Fuca Strait during periods of neap tides. These currents are the dominant mechanism for deep-water renewal in the Strait of Georgia. It is argued that these currents are baroclinically unstable and that the stability characteristics are reasonably consistent with the observed structure of the low-frequency current fluctuations. The episodic nature of these unstable bottom flows may help to explain the spatial and temporal variability of the low-frequency current fluctuations observed in the Strait of Georgia.