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Journals 2005/2006

James J. Dornicik
Ward Melville High School, East Setauket, New York

"Investigating Vertical Mixing at Eddy A4"
R/V Oceanus
July 14 - August 5, 2005
Journal Index:
July 14 - 15 - 16 - 17 - 18 - 19 - 20
       21 - 22 - 23 - 24 - 25 - 26 - 27
        28 - 29 - 30 - 31
August 1 - 2 - 3 - 4 - 5

July 18, 2005
Steaming to eddy A4 and finding the center of the eddy

We set sail at 07:00 from St. Charles Harbor in Bermuda. We have about a 12-hour steam to the edge of the eddy where the crews' research will begin. To find the eddy's center we will be using two measurement techniques. The first is an Acoustic Doppler Current Profiler or ADCP. What the ADCP does is send a pulse down and detects the different refraction at various depths and times. This allows us to determine which way the current is flowing and allows us to determine the edges of the eddy and ultimately determine the center of the eddy.

Just for everyone's sake an eddy is a vortex of water that spins around similar to a washing machine. We will also be determining the water temperature in the water column using an Expendable Bathy Thermograph, XBT for short. An XBT is a torpedo shaped instrument with a temperature sensor in it. The XBT is launched in a small tube and data on temperature is sent back to the computer via a small twin conductor wire. Once the test is done the wire is broken and the test is complete.

The center of the eddy can be determined by a temperature profile. The temperature at 700 meters will rise from 12°C to around 18°C at the center of the eddy. The following is the time and temperature data for the XBT.

Test Time Temp.
XBT#1 16:30 12°C
XBT#2 17:31 12°C
XBT#4 19:31 14°C
XBT#5 20:30 14.21°C
XBT#6 21:31 14.67°C
XBT#7 22:31 14.51°C
XBT#8 23:31 13.6°C
XBT#9 00:35 14.04°C
XBT#10 01:35 13.86°C

After XBT # 10 my shift was over and I went to sleep. The ADP scans and the XBT were continued until we hit the exact eddy center.