%======================================================================
%                    I N T R O / F L A M E 2 . T E X 
%                    doc: Wed Sep 30 14:45:35 1998
%                    dlm: Wed Jun  7 21:55:36 2000
%                    (c) 1998 A.M. Thurnherr
%                    uE-Info: 60 0 NIL 0 0 72 3 2 4 ofnI
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\begin{figure}[t]

\placeFig[.9]{intro/F2_stations}

\caption[1998 stations \FFp{(}{)}]{\FFp{}{ } CTD stations; shading is the
same as in \protect\rfigNP{AMAR-bridge}; contour interval is \m{500};
full-depth CTD stations are marked with big stars; the small stars near
\latN{35}{35}/\lonW{34}{15} show the bottom turning points of a CTD
tow-yo \protect\rfig{F2-inflow}; black stars with white borders indicate
profiles extending below \m{2550}.}

\labelFig{F2-stations}

\end{figure}

In June/July 1998 the \A segments were revisited during the \FF cruise,
the main purpose of which was the recovery of eight moorings with 25
current meters deployed in 1997 \rsec{CM-methods}. To investigate the
low-frequency variability of the hydrography and of the particle plume
the \R region was re-sampled. Because of favorable weather conditions
sampling was extended in both directions along the rift valley to cover
the \sA and \A segments. \rFigNP{F2-stations} shows the locations of
the tow-yo and the full-depth stations occupied during the \d{6} of
sampling. In addition to the stations shown, the eastern off-ridge
background station of the \F cruise \rsec{F-methods} was re-occupied
for reference.

Because of instrument problems, two separate \emph{Neil-Brown Mk.IIIb}
CTDs were used on a platform which was also equipped with a \emph{Sea
Tech Light Scattering Sensor} (LSS), a 12-bottle sampling rosette, and
auxiliary instruments such as an altimeter. The temperature sensor of
one of the two CTDs was pre-cruise calibrated (the other instrument was
taken as a spare).

To calibrate the temperature sensors, the first sampling bottle of the
CTD rosette was fitted with two digital reversing thermometers,
pre-cruise calibrated to \degC*{\pm2}{-3}. Near-bottom temperatures
were recorded at 23 out of the 35 CTD stations. The average of the two
thermometer readings was used for calibration. RMS errors of the
temperature calibrations for the two CTDs are \degC*{1.2}{-3} and
\degC*{1.5}{-3}, respectively.

The conductivity sensors of both CTDs were calibrated by analyzing 34
and 158 bottle samples with an \emph{Ocean Scientific International
AUTOSAL Model 8400A} salinometer, resulting in RMS errors of
\psu*{1.8}{-3} and \psu*{3.3}{-3}, respectively. The conductivity
sensor accuracy of \Spm*{5}{-6} corresponds to a salinity accuracy of
\psu*{6}{-3} at \degC{4} and \dbar{3000}.

The LSS was not calibrated and instrument voltage anomalies with
respect to the observed mean between \m{1500} and \m{1850} are used as
the ``nephel'' unit (c.f.\ \rsecNP{F-methods}).

