In spring of 1998 three Moored Profilers were deployed in concert on the continental slope off the Virginia in a short-term process experiment called TWIST (Turbulence and Waves over Irregularly Sloping Topography). The instruments were deployed in a triangular array and programmed to profile together making 16 profiles each day. The following figure shows a depth-time contour plot of potential temperature derived from one of the instruments. Time is depicted here relative to the beginning of the deployment.
Fortnightly modulation of the semi-diurnal baroclinic tide is readily
apparent, becoming particularly intense at and after deployment day 13..
Note also the warming trend at the surface which is linked to the meandering
of the Shelf Break Front at that time, moving seaward toward the mooring
sites. In addition one can see the smaller scale structure which is the
energetic internal wave field.
The corresponding across- and along-isobath components of absolute velocity from this instrument are shown below.
These two figures illustrate the potential of the moored profiling system for high resolution velocity measurements. In each, the direction of the flow is differentiated by both color and contour line style: blue shading and solid contours denotes offshore and along-isobath flow to the northeast; onshore and southward along-isobath flow is marked in red with broken contour lines. Near zero current speed is green. The contour interval here is 5 cm/s.
A short test deployment of a McLane Moored Profiler was carried out
in January 2001 off Kaena Point, Hawaii. This system cycled continuously
for a 3-1/2 day period returning profiles approximately every 1.5 hours
between ~600 and ~1600 m depth. The test returned interesting information
about the internal tide generated by flow over the Hawaiian Ridge.
Vertical motions of isopycnals caused by the baroclinic internal tide (above) are in phase with the meridional tidal currents (below), indicative of a horizontal energy flux by the internal tide. One can also see a slight vertical tilt to the velocity contours (upward phase propagation in time) that is consistent with downward energy propagation by an internal wave.
In support of colleagues from the Institut fur Meerskunde, Kiel Germany, a WHOI Moored Profiler was prepared and loaned to them for a 10-month deployment in the Labrador Sea spanning winter 1999-2000. Below left, you may view the depth-time contour plot of potential temperature from this deployment. The time axis in this case begins on July 26, 1999. Note the three warm-core eddies that passed the mooring site in late summer 1999, the cooling at the surface that penetrates to the sampling level by day 130, the deep mixed layers seen in late February 2000 (~day 210) and the restratification that begins shortly thereafter. The panel to the right shows the potential density data acquired on February 23, 2000 showing a near-uniformly well mixed surface layer extending down to about 1000 m depth.
A WHOI Moored Profiler was deployed in the Deep Western Boundary Current of the Weddell Sea for 12 months beginning in April 1999. The figures below show depth-time contour plots of potential temperature, salinity and along-isobath velocity obtained from that instrument. Variability on a host of time scales is evident in the figures. Most notable is a long-period strengthening then weakening in the intensity of the along-isobath, bottom-intensified flow that is seemingly associated with a baroclinic uplift then relaxation of isopycnals (and isotherms, isohalines) at the boundary that is responsible for the near-bottom water property variations that are observed.
As detailed in another part of this site, many other instruments are now going into the field. This site will be updated as new data sets accumulate.