US JGOFS Antarctic Environments Southern Ocean Process Study (AESOPS)
 
Palmer Leg 98-02; 24 Feb.-3 April 1998
 
Documentation for: THE HYDROGRAPHIC BOTTLE DATA 

L.A. Codispoti (lou@ccpo.odu.edu)
Old Dominion University,  August, 1998


General Comments:

This "readme" file pertains to the salinity data taken from the
hydrographic rosette that was equipped with  ~10-liter
"Niskin-like" Bullister Bottles made mostly of PVC during Palmer
leg 98-02 (24 Feb.-3 April 1998).

Dr. Susumo Honjo (shonjo@whoi.edu) of the Woods Hole
Oceanographic  Institution was the chief scientist during this
leg.  This cruise was the last AESOPS Leg, and its main purpose
was to recover the JGOFS sediment trap and optical array
moorings, and to collect additional data at the mooring sites. 

No units are given for salinity in this report because the most
recent definitions of salinity define it as a dimensionless
number.  Some questionable data have not been submitted, but they
are available upon request (lou@ccpo.odu.edu).


Temperature:

The temperature data associated with each bottle depth were taken
by the CTD system during the bottle tripping process.  Consult
the companion CTD data report for this cruise to learn more about
the CTD system.


Sampling:

The samples in this report were taken from ~10 liter Bullister
bottles. 

Because there is little or no lag time between triggering a
bottle and bottle closure with the new SeaBird rosette systems,
bottles were generally held at the sampling depth for at least 30
seconds before tripping or until the deck read-outs stabilized if
this took more than 30 seconds.  NOTE THAT THIS TIME INTERVAL WAS
NOT ALWAYS SUFFICIENT TO ALLOW FOR COMPLETE FLUSHING OF THE
BULLISTER BOTTLES.  EXAMINATION OF DATA FROM STRONG SALINITY
GRADIENTS SUGGESTS THAT IN A FEW CASES THE EFFECTIVE DEPTH OF THE
SALINITY SAMPLE COULD BE UP TO ~5 M DEEPER  THAN THE INDICATED
DEPTH, BUT, IN GENERAL, THESE DATA ARE NOT SIGNIFICANTLY BIASED
BY THIS PROBLEM.

NOTE THAT THE MID-POINT OF THE SAMPLING BOTTLES WAS ~1m ABOVE THE
CTD SENSORS.  THE DATA HAVE NOT BEEN CORRECTED FOR THIS OFFSET.


Salinity:

In general, the methods employed for the bottle salinity
determinations did not differ significantly from those described
in the JGOFS protocols that were distributed in 1994 (UNESCO, IOC
Manual and Guide #29). 

Salinities were determined with Guildline Autosal salinometers.
New vials of standard sea-water were used to standardize before
and at the end of every run. Agreement between bottle salinities
and the primary sensors on the SeaBird CTD systems was usually
better than ~0.025 (except in regions of strong gradients) before
post-cruise data processing which employs the bottle salinities
to correct the CTD salinities. More information on the quality of
the salinity data are given in the companion CTD report.  Both
the CTD salinity data at the time of bottle tripping and the
salinities run on the Niskin bottle samples with an Autosal
salinometer are reported here.

NOTE THAT TEMPERATURE CONTROL AND POWER PROBLEMS IN THE AUTOSAL
ROOM MAY HAVE SLIGHTLY DEGRADED THE AUTOSAL SALINITY DATA FROM
THIS CRUISE AND THAT THE ERRORS MAY HAVE, AT TIMES, EXCEEDED THE
WOCE STANDARD OF 0.002. THE USER CAN ESTIMATE THIS EFFECT FOR
MANY CASTS BY EXAMINING DATA FROM THE LARGE PROPORTION OF
REPLICATE SAMPLES THAT WERE COLLECTED.