Dataset: CTD_MOCNESS.25

The MOCNESS is based on the Tucker Trawl principle (Tucker, 1951). The particular MOCNESS system from which these CTD data came is one of three net systems. The MOCNESS-.25 carries nine rectangular nets (1/4-m²), usually with 64 micrometer mesh. In all three MOCNESS systems, the underwater unit sends a data frame, comprised of temperature, depth, conductivity, net-frame angle, flow count, time, number of open net, and net opening/closing, to the deck unit in a compressed hexadecimal format every 2 seconds and from the deck unit to a microcomputer every 4 seconds. Temperature (to approximately 0.01 deg C) and conductivity are measured with SEABIRD sensors. Normally, a modified T.S.K.-flowmeter is used. Both the temperature and conductivity sensors and the flowmeter are mounted on top of the frame so that they face horizontally when the frame is at a towing angle of 45deg. Calculations of salinity (to approximately 0.01 o/oo S), potential temperature (theta), potential density (sigma), the oblique and vertical velocities of the net, and the approximate volume filtered by each net are made after each string of data has been received by the computer. (Wiebe et al., 1985) In addition, data were collected from four other sensors attached to the frame: the Transmissometer, the Fluorometer, the Downwelling light sensor, and the Oxygen sensor. A SeaBird underwater pump was also included in the sensor suite.

It should be noted that whenever the data are of questionable value, 50.000 is written in the particular data field.

Unless otherwise indicated, these data have not been post-processed.

For additional information, contact the chief scientist for the cruise or the U.S. GLOBEC Data Management Office (DMO).

Note: Some variables have been eliminated from the display but are nevertheless available. These variables include: oxycurrent, oxytemp, tempco, and echo.

References

Fofonoff and Millard, 1983, UNESCO technical papers in Marine Sciences, #44.

Tucker, G.H., 1951. Relation of fishes and other organisms to the scattering of underwater sound. Journal of Marine Research, 10: 215-238.

Wiebe, P.H., K.H. Burt, S. H. Boyd, A.W. Morton, 1976. The multiple opening/closing net and environmental sensing system for sampling zooplankton. Journal of Marine Research, 34(3): 313-326.

Wiebe, P.H., A.W. Morton, A.M. Bradley, R.H. Backus, J.E. Craddock, V. Barber, T.J. Cowles and G.R. Flierl, 1985. New developments in the MOCNESS, an apparatus for sampling zooplankton and micronekton. Marine Biology, 87: 313-323.

updated September 30, 2008. mda