As a suggestion, a nice test area to assess the relative performance
of the new ES-150 against the OS-38 is the Juan de Fuca Canyon.
A canyon really only in name - it is a deep across-shelf trough that
joins the open ocean to the mouth of the Strait of Juan de Fuca. It
acts as a passageway to feed colder nutrient rich waters into the
Strait and ultimately the Salish Sea region (Puget Sound and the
Georgia Basin). Because there is a lot of vertical water column
shear and longitudinal gradients in the currents, it should be an
interesting place to compare the relative performance of these
comparable ADCP systems.
showing the mouth of the Strait of Juan de Fuca
and the link between it and the shelf break, formed by the Juan de Fuca "canyon". The black line indicates the proposed transect.
The white box shows the bounds of the more detailed figure
below. Superimposed is the NOAA chart showing the
shipping lanes
The transect is 85.2 km (46 nm) and would take about 5.8 hours to
cover running at 8 knots. Note that it starts in the outgoing
shipping lane, but thereafter is outside the main shipping traffic.
It is (presumably) an only slightly circuitous path on the way to
the shelf break that the vessel will going anyway in order to
reach deep water.
A close up view is presented here (using GMRT bathymetry):
rotated map sheet showing the transect in
detail (100m contour interval)
vertical depth profile along the proposed
transect (note the sill at the SW end).
The idea is to run this transect just as part of a transit (in
and/or out) during the pre-testing period. And perhaps on the way
out for the first testing leg.
Originally my idea was to then focus on the sill at the mouth, and
run back and forth along a 8 nm (1 hour) section for the duration of
one M2 tidal period (so would cost 13 hours). It would have been
nice to have the bottom mounted ADCP just in the landward side of
the sill - but the logistics of dropping it there and needing to
pick it up later, are not practical.
In it, they show that there is a two level system. Above the depth
of the surrounding shallower shelf (~< 140m) the watermasses are
moving back and forth with tidal frequencies. Below that depth (>
150m) within the constraints of the canyon, there is net upstream
(landward) flow of deeper (nutrient rich of course) water. Between
the two watermasses, there is significant shear. The most
interesting aspect of the study is the behaviour of the flow as one
goes over the constraining sill at the shelf break. At this location
they report a strong lee wave response with overturns (large scale
turbulence).
The canyon axis is all > 200m, with local holes down to 380m and
is thus an ideal area to test the performance of these lower
frequency ADCPs. The WH300 will only look at the top 100m (at best),
but the OS38 will see all of it (and much deeper if available). The
ES-150 is a not yet a very well known system. But at 150 kHz it
should be able to image the whole water column.
Suggested Data Collection:
OS38 - 10m(?) bins broad band - max range 600m
WH300 - 2m bins broad band - max range 100m
ES-150 - however KM suggest it be set up (perhaps alternating
pings ,oblique and splitbeam nadir?) - max range 600m.
EM712 - logging water column +/-65 deg, forced to Medium Mode
(all CW).
EM124 - logging water column +/- 65 deg forced to shallow mode
(default).
EM2040 - sonar mode - forced to FM - 100m range. (un-synched)
ES-200 - logging 1ms CW
ES-38 - logging 1ms CW
MVP-300 dipping every 15 minutes to max depth (20m off
bottom)?.
Quite how the synchronization should proceed, I'm not sure. All
could be unsychronized?. Testing could be done in the transit down
the Strait as all about the same depth. The EK-80's do NOT have to
be on as they are not being tested. I suspect they would be synch'ed
with the ES-150 anyway.
Other MBES WCD data samples
To get an idea about what we might find here, I've browsed the NCEI
water column archives and found 4 MBES systems that transit through
the area:
You'll see there is a noticeable scattering horizon separating the
upper shelf waters from the isolated canyon waters.