To: SPURS investigators
Re: SPURS cruise planning
Date: May 24, 2012
I have been working on the cruise plans for our upcoming SPURS
field work and welcome your input and feedback on this general outline.
A more detailed breakdown of the shiptime is in the works but I wanted
to share this outline to get us all on the same page.
Some basic constraints for the Knorr cruise:
Dates: Depart WH Sept. 6 - Arrive Ponta Delgada, Azores, Oct. 9, 33 days at sea
Distances: It is 1915 nm from Woods Hole to 25N, 38W, about 8 days of steaming.
It is 993 nm from 25N, 38W to Ponta Delgada, about 4 days of steaming.
This gives our working time on site of about 21 days.
My thinking is that we can spend roughly one week deploying
assets, including moorings, floats and gliders, about one week doing a
small "control volume" with repeat surveys around the moorings, and
about one week doing a feature survey, targeting a front or eddy
identified by the satellites and models. Of course, we must always
figure on some time lost to weather or chasing down the errant glider,
but this is a general outline.
The moorings will require bathymetric surveys of the sites
before finalizing line lengths; Tom requests that we do the surveys for
all three sites first so as to give time for the mooring groups to set
up. Surveying will not take long, and can be done at night; the three
moorings should take no longer than three days to deploy, so long as the
weather is reasonable. Obviously, some gliders, floats and drifters
could be deployed during this time as well.
Steve is planning deployment of his 25 profiling floats in a 5 x
5 grid with 30 km spacing. If we steam this with a "radiator" pattern
(with approximately upwind/downwind legs) this would take about 2 days.
I imagine this would be the best time to deploy the gliders, though I
understand that they can self-position and get to their survey lines on
their own, so could be deployed as soon as we are in the area.
The control volume around the moorings will be done with an
Under Way CTD while steaming, ships ADCP, then microstructure and
CTD/LADCP casts at the corners. The idea is to hit the corner stations
on a 7 hour cycle, so we get four in an inertial period (~28 hrs). The
corners could be the moorings or some wider square. A turbulence glider
would also be doing the legs, and it may be an excellent pattern for a
wave glider as well. If we do this for 6 days we cover 5 inertial
periods.
This would allow us about a week to chase down and survey an
interesting feature (front or eddy) suggested by the satellites and
models. Surveys could be stars (eddy) or butterflys (front) and the
UW-CTD, CTD/LADCP and microstructure profiles will be appropriate
assets. This gives us an opportunity for discovery. One option is to
steam south into a region with stronger surface salinity gradients,
though there would be some loss in survey time. A cluster deployment of
surface drifters would be possible if the drifter working group decides
this is worthwhile. The working group is presently discussing
deployment strategies.
I am looking for feedback on this general plan. Let me know
your specific deployment needs, so that we can work them into the
detailed plans. I want to know about expectations for things like
whether CTD casts are required on deployment of various assets. (I
understand that none are needed for the floats, but how about for the
gliders?). Do the mixed layer floats require a steam to the east to get
"up-stream"f the site? If so, how far?
Let me know your expectations for your participation in the cruise and I will work them into the detailed plan.
Thanks,
Ray
Sound good
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