The Fraser River freshet is starting (snow pack melt in the coastal mountains), and the suspended sediment loads coming out of the river mouth into the Strait of Georgia are also increasing. This is especially evident at our...
The VENUS observatory measures the tide and large surface waves with our pressure sensors, but internal waves also exist and can sometimes been seen in the inverted echo-sounder data. Here is a one hour record of the 200 kHz ZAP inverted echo-sounder data from the Delta Dynamics Laboratory (DDL) on 11 January 2012 (20:00 UTC). The train of solitary internal waves shows up as an undulating layer of scattering material in the upper 20m.
Internal waves are generated when an “internal” density interface is disturbed. The ocean is stratified in density, with dense sea-water always underlying less dense (lighter) sea-...
Dynamic sediments and sediments with active biogeochemistry often generate a variety of chemical compounds, some of which will be gaseous. This inverted echo-sounder image from 30 October 2011 at the Delta Dynamics Laboratory in the Strait of Georgia at 108m water depth near the mouth of the Fraser River has captured numerous clouds of rising bubbles. Such bubbles have several...
The ASL Zooplankton Acoustic Profiler (ZAP) located at the base of the slope of the Fraser Delta recorded this hourly image of echo-sounder backscatter between 4:00 and 5:00 UTC September 5, 2011 (21:00 – 22:00 PDT September 4, 2011, just after dusk and at rising tide). The image reveals a dense school of large fish between 10 and 20m depth, and many individual fish...
The Parascientific Pressure sensor located at our Fraser Delta site caught the oceanic signal of the local 6.3 earthquake of September 9, 2011 (12:41 PDT). The pressure sensor is located on a bottom mounted platform and samples at a rate of ~700 ms. The background trend is the rising tide, on which is superimposed the surface pressure signature of tsunami like waves “sloshing” about in the Strait of Georgia. The signal also shows up in other pressure sensors at this and our...
During rising and high tide, the sea pushes back against the Fraser River, reducing its flow at the mouth. As the tide ebbs, approaching low tide, the flow at the river mouth increases, and the sediment laden river water is “released/floods” into the Strait of Georgia. The river water, especially during periods of faster moving flow, is laden with silt and fine sands. As the flow...
