Dataset: bottle
Deployment: TT053

Hydrographic Data: temp, salinity, nutrients from Niskin bottles

Principal Investigator:

Dr Louis A. Codispoti (Old Dominion University, ODU)

Co-Principal Investigator:

John M. Morrison (North Carolina State University - Marine, Earth and Atmospheric Sciences, NCSU MEAS)

BCO-DMO Data Manager:

Cynthia L. Chandler (Woods Hole Oceanographic Institution, WHOI BCO-DMO)

Project:

U.S. JGOFS Arabian Sea (Arabian Sea)

Version:

May 8, 2000

Deployment Synonyms:

TTN053, TN053, TTN-053

Version Date:

2000-05-08

Data URL:

https://www.bco-dmo.org/dataset-deployment/450675/data

Expand/Collapse All

Description

Hydrographic Data: temp, salinity, nutrients from Niskin bottles

Methods & Sampling

Dataset acquisition description

See Platform deployments for cruise specific documentation

Final Corrections to Arabian Sea Niskin Bottle Data

performed at US JGOFS DMO October 28, 1996


From: Lou Codispoti 
Subject: Final Corrections

Dear JGOFS investigator, This is to inform you that some minor corrections were made to the JGOFS Arabian Sea nutrient data after the 1996 meeting in New Hampshire. It is doubtful that any of these corrections will alter any of your hypotheses, but they may have some significance in documenting changes over long periods of time, and in WOCE-style investigations. The need for these corrections arose, as a consequence of post-cruise re-calibration of pipets, and because we did not properly account for the nutrient content of our low nutrient sea-water. The corrections have already been applied to the US JGOFS Arabian Sea nutrient data collected with the hydrographic rosette, by personnel at WHOI who maintain the US JGOFS data. I list them here for your information. 1) All ammonium and nitrite data from Thompson leg TN053 were multiplied by 0.997. 2) All ammonium and nitrite data from ALL US JGOFS Arabian Sea cruises (TN039, 043, 045, 049, 050, 053 and 054) were multiplied by 0.995. 3) ALL phosphate data from ALL US JGOFS Arabian Sea cruises (TN039, 043, 045, 049, 050, 053 and 054) were multiplied by 0.992. Corrections 2) and 3) should probably be applied to the ONR data as well, but I will leave this up to Burt Jones, as I am not exactly sure how he did his standardizations. Basically, corrections 2) and 3) arise from a failure to take into account dilution of the Low Nutrient Sea Water signal by standards in cases where the LNSW contains appreciable quantities of nutrients. The above corrections are pretty minor within the scheme of nutrient analyses, but we should always attempt to eliminate such systematic errors. George and Chris have made these corrections on the US JGOFS Arabian Sea nutrient data collected from the hydrographic rosette. Trace metal rosette data and experimental data have not yet been corrected. Cheers, Lou Codispoti +---------------------------------+------------------------------------------+ | Louis Codispoti | Center for Coastal Physical Oceanography | | Research Professor | Old Dominion University | | lou@ccpo.odu.edu | Norfolk Virginia, 23529 USA | | http://www.ccpo.odu.edu/ | PH: 804-683-5770 FAX: 804-683-5550 | +---------------------------------+------------------------------------------+

US JGOFS Data Management Office Note Regarding Calculated Depth

 The depth values in the bottle file have been calculated from pressure
 using the algorithm below.

 The US JGOFS Data Management Office is the source of the calculations.

 The latitude used in computation was the lat_begin of the bottle file.

 The CHECKVALUE was used to verify the accuracy of the computation.

 The stated accuracy of this algorithm is 0.1 meters
 
 Thanks to Edward Peltzer (MBARI) for supplying the algorithm and for
 discussions regarding the computation.

function DEPTH=depth(P,LAT); DEPTH Computes depth given the pressure at some latitude D=DEPTH(P,LAT) gives the depth D (m) for a pressure P (dbars) at some latitude LAT (degrees). Fofonoff and Millard (1982). UNESCO Tech Paper #44. Notes: (ETP3, MBARI) This algorithm was originally compiled by RP @ WHOI. It was copied from the UNESCO technical report. The algorithm was endorsed by SCOR Working Group 51. The equations were originally developed by Saunders and Fofonoff (1976). DSR 23: 109-111. The parameters were re-fit for the 1980 equation of state for seawater (EOS80). CHECKVALUE: D=9712.653 M FOR P=10000 DECIBARS, LAT=30 DEG CALCULATON ASSUMES STD OCEAN: T = 0 DEG C; S = 35 (IPSS-78) X = sin(LAT/57.29578); X' = X*X; GR = GRAVITY VARIATION WITH LAT: ANON (1970) BULLETIN GEODESIQUE GR = 9.780318*(1.0+(5.2788E-3+2.36E-5*X')*X') + 1.092E-6*P D = DEPTH BEFORE GRAVITY CORRECTION D = (((-1.82E-15*P+2.279E-10)*P-2.2512E-5)*P+9.72659)*P DEPTH = D/GR

Deployment-specific acquisition description

   PI:              Louis Codispoti
   of:              Old Dominion University
   dataset:         Temp, salinity, nutrients from Niskin bottles
   dates:           October 29, 1995 to November 25, 1995
   location:        N: 24.3329  S: 10.0823  W: 56.4858  E: 67.1784
   project/cruise:  Arabian Sea/TTN053 - Process Cruise 6 (bio-optics)
   ship:            Thomas Thompson

US JGOFS Arabian Sea Cruise: TN053
        HYDROGRAPHIC BOTTLE DATA


L.A. Codispoti (lou@ccpo.odu.edu)
Old Dominion University, June 1996

General Comments:

This "readme" file pertains to the salinity, dissolved oxygen, and
nutrient data taken from sampling bottles with the hydrographic
rosette that was equipped with 24 10-liter Niskin type bottles during
RV T.G. Thompson cruise TN053. This cruise was the sixth JGOFS
Arabian Sea Process Leg and took place during Oct.-Nov. 1995.
Dr. William M. Balch of the Bigelow Laboratory for Ocean Sciences
(bbalch@bigelow.org) was the chief scientist.

NOTE THAT MULTIPLE CASTS WERE TAKEN AT MOST STATIONS AND THAT, IN SOME
CASES, THE GEOGRAPHIC POSITIONS OF CASTS AT THE SAME STATION MAY VARY
SIGNIFICANTLY.

Some questionable data are not included in this report. These data are
still retained in files at Old Dominion University and are available
upon request. 

No units are given for salinity in this report because the most recent
definitions of salinity define it as a dimensionless number.  To
accommodate every preference, Winkler oxygen values are reported in
ml/l, micromolar and micromoles per kg.  The latter values can only be
calculated with a knowledge of the oxygen sample temperatures when the
samples were drawn. These "draw temperatures" are not reported here,
but can be obtained by contacting lou@ccpo.odu.edu.  Nutrient values
are reported in micromolar. They can be converted to micromoles per
kg, by combining laboratory temperature on the Thompson (approx. 25
deg C during this leg) and the salinity of the sample to compute
density and then dividing the value in micromolar by this number. NOTE
THAT AIR CONDITIONING PROBLEMS DURING THIS LEG CAUSED LABORATORY
TEMPERATURES TO RANGE FROM ~23-27 DEGREES.

Final Corrections

performed at US JGOFS DMO October 28, 1996

From: Lou Codispoti 
Subject: Final Corrections

Dear JGOFS investigator,

This is to inform you that some minor corrections were made to the
JGOFS Arabian Sea nutrient data after the 1996 meeting in New
Hampshire.  It is doubtful that any of these corrections will alter any
of your hypotheses, but they may have some significance in documenting
changes over long periods of time, and in WOCE-style investigations.

The need for these corrections arose, as a consequence of post-cruise
re-calibration of pipets, and because we did not properly account for
the nutrient content of our low nutrient sea-water.

The corrections have already been applied to the US JGOFS Arabian Sea
nutrient data collected with the hydrographic rosette, by personnel at
WHOI who maintain the US JGOFS data. I list them here for your
information.

1) All ammonium and nitrite data from Thompson leg TN053 were
multiplied by 0.997.

2) All ammonium and nitrite data from ALL US JGOFS Arabian Sea cruises
(TN039, 043, 045, 049, 050, 053 and 054) were multiplied by 0.995.

3) ALL phosphate data from ALL US JGOFS Arabian Sea cruises (TN039,
043, 045, 049, 050, 053 and 054) were multiplied  by 0.992.

Corrections 2) and 3) should probably be applied to the ONR data as
well, but I will leave this up to Burt Jones, as I am not exactly sure
how he did his standardizations.  Basically, corrections  2) and 3)
arise from a failure to take into account dilution of the Low Nutrient
Sea Water signal by standards in cases where the LNSW contains
appreciable quantities of nutrients.  The above corrections are pretty
minor within the scheme of nutrient analyses, but we should always
attempt to eliminate such systematic errors.

George and Chris have made these corrections on the US JGOFS Arabian Sea
nutrient data collected from the hydrographic rosette. Trace metal
rosette data and experimental data have not yet been corrected.

Cheers, Lou Codispoti

-- 
+---------------------------------+------------------------------------------+
| Louis Codispoti                 | Center for Coastal Physical Oceanography | 
| Research Professor              | Old Dominion University                  | 
| lou@ccpo.odu.edu                | Norfolk Virginia, 23529 USA              |
| http://www.ccpo.odu.edu/        | PH: 804-683-5770  FAX: 804-683-5550      |
+---------------------------------+------------------------------------------+


 The depth values in the bottle file have been calculated from pressure
 using the algorithm below.

 The US JGOFS Data Management Office is the source of the calculations.

 The latitude used in computation was the lat_begin of the bottle file.

 The CHECKVALUE was used to verify the accuracy of the computation.

 The stated accuracy of this algorithm is 0.1 meters
 
 Thanks to Edward Peltzer (MBARI) for supplying the algorithm and for
 discussions regarding the computation.



 function DEPTH=depth(P,LAT);

  DEPTH   Computes depth given the pressure at some latitude
          D=DEPTH(P,LAT) gives the depth D (m) for a pressure P
              (dbars) at some latitude LAT (degrees).

          Fofonoff and Millard (1982). UNESCO Tech Paper #44.

  Notes:  (ETP3, MBARI)
          This algorithm was originally compiled by RP @ WHOI.
          It was copied from the UNESCO technical report.
          The algorithm was endorsed by SCOR Working Group 51.
          The equations were originally developed by Saunders
              and Fofonoff (1976).  DSR 23: 109-111.
          The parameters were re-fit for the 1980 equation of
              state for seawater (EOS80).

  CHECKVALUE: D=9712.653 M FOR P=10000 DECIBARS, LAT=30 DEG

  CALCULATON ASSUMES STD OCEAN: T = 0 DEG C; S = 35 (IPSS-78)


  X = sin(LAT/57.29578);
  X' = X*X;


  GR = GRAVITY VARIATION WITH LAT: ANON (1970) BULLETIN GEODESIQUE

  GR = 9.780318*(1.0+(5.2788E-3+2.36E-5*X')*X') + 1.092E-6*P


  D = DEPTH BEFORE GRAVITY CORRECTION

  D = (((-1.82E-15*P+2.279E-10)*P-2.2512E-5)*P+9.72659)*P

  DEPTH = D/GR

Data Processing Description

Dataset Processing Description

Methods:

In general, the methods employed for the bottle salinity, Winkler
dissolved oxygen, and nutrient analyses did not differ significantly
from those described in the JGOFS protocols that were distributed in
June, 1994. Minor differences included the following: 

1) Sea Bird CTD systems and bottle carousels were employed (SBE-9+ underwater 
units, SBE-11 deck units, SBE-32 carousels).  These units  represent a newer 
generation of equipment than the units described in the JGOFS protocols.  

2) The weights of the salts used for primary standards for dissolved oxygen 
and nutrients were not adjusted to an "in vacuo" basis as suggested in 
the protocols. It is unlikely that this departure from procedure would 
cause significant errors. Our calculations suggest that the maximum 
differences arising from our decision to not correct to an "in vacuo" 
basis would range from 0.02% (oxygen standards) to 0.06% (ammonium standards).  

3) The protocols give one a choice of adjusting nutrient methods so that 
calibration curves are strictly linear, or opting for more response and 
taking into account non-linearities.  We choose the latter method.  

4) No corrections were made for "carryover" between nutrient samples run 
on the Technicon Autoanalyzer. Data from this cruise, suggest that
carryover effects in our nutrient analyses are generally less than ~2%
of the concentration difference between adjacent samples. Examination
of cases where more than one sample was taken from a depth at which
there was a significant increase in nutrient concentrations will help
the user determine the carryover effect for many individual casts. 

5) Calibration and re-calibration of volumetric ware were not exactly as
described in the JGOFS protocols, but this was largely compensated for
by comparing independent standards diluted with independent volumetric
ware, and by re-calibration of some of the volumetric ware after
cruises TN045 and TN050. WE HAVE NOT YET RECALIBRATED THE VOLUMETRIC
WARE USED DURING TN053. WE WILL UPDATE THE DATA IF RECALIBRATION
SUGGESTS A NEED TO DO THIS, BUT WE DO NOT EXPECT SIGNIFICANT CHANGES

6) Duplicate oxygen samples were not drawn from every Niskin or Go-Flo
bottle, but there were several comparisons of bottles tripped at the
same depth.  

7) Azide was added to the Winkler oxygen pickling reagents to destroy 
nitrite that can be present in relatively high concentrations in the 
Arabian Sea. ON LEGS PRIOR TO TN053, OXYGEN STANDARDIZATIONS WERE RUN USING 
REAGENTS THAT DID NOT CONTAIN AZIDE, BUT DISCUSSIONS AND TESTS SUGGESTED THAT 
IT WOULD BE BETTER TO STANDARDIZE WITH AZIDE, DESPITE SOME CONFUSION IN THE 
LITERATURE ON THIS MATTER.  CONSEQUENTLY, WE SWITCHED PROCEDURES BEGINNING WITH  
LEG TN053 AND USED REAGENTS CONTAINING AZIDE TO STANDARDIZE.  OUR TESTS SUGGEST 
THAT THE MAXIMUM CHANGE IN OXYGEN CONCENTRATIONS ARISING FROM THIS CHANGE WOULD 
OCCUR AT THE HIGHEST OXYGEN CONCENTRATIONS AND BE < ~0.01 ML/L.

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 Niskin
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 THE MID-POINT OF THE SAMPLING BOTTLES WAS ONE METER ABOVE
THE CTD SENSORS.  THE DATA HAVE NOT BEEN CORRECTED FOR THIS ONE METER
OR 1.01 DECIBAR DIFFERENCE BETWEEN CTD SENSOR AND SAMPLING BOTTLE
POSITIONS.

Salinity:

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 recently
calibrated sensors on the Sea Bird CTD systems was usually better than
0.02 (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.

Dissolved oxygen:

The Winkler dissolved oxygen set-up was built and supplied by the
SIO/ODF group.  This system is computer controlled and detects the
end-point photometrically.  Temperature of the thiosulfate and
standard solutions is automatically monitored by this system.  Checks
on cruises TN039 and TN043 between independent standards prepared with
independent volumetric ware gave agreement of +-0.02 per cent. A
similar check made during TN054 suggested agreement of better than
+-0.15 per cent. The linearity of the "Dosimat" automatic buret was
also checked during cruises TN043 and TN054 with good results.


Nutrients:

Note that the terminology used to describe nutrients has become
somewhat loose over the years and that silicate=silicic acid, and 
phospate=reactive phosphorus.

Nutrient analyses were performed on a 5-channel Technicon II AA
system that was modified and provided by the SIO/ODF group.

In assessing the nutrient standard comparisons outlined below,
note that the full-scale ranges for nutrients were as follows:
Ammonium  =0 to   5  micromolar
Nitrate   =0 to  45  "
Nitrite   =0 to   5  " 
Phosphate =0 to   3.6"
Silicate  =0 to 180  "

These ranges were arrived at after an Internet poll of PI's and were
selected to cover the full depth concentration range for the Arabian
Sea. Since, we found nitrite concentrations that exceeded 5 micromolar
on several occasions, the nitrite concentration range was expanded
to 0-7 micromolar on leg TN050.

On the set-up and calibration cruise (TN039), the SIO/ODF nitrate and
nitrite standards and standards from the National Institute of
Oceanography in India (provided by S.W.A.  Naqvi) were compared with
the following results:

NIO Nitrate Std.= 22.6 micromolar; SIO/ODF=22.5 micromolar
NIO Nitrite Std.=  2.42 micromolar; SIO/ODF = 2.50 micromolar
As can be inferred from the above, the nitrate plus nitrite
values were almost identical in the mixed standards;
25.02 (NIO) vs 25.00 (SIO)micromolar.

On TN039, Lou Codispoti prepared independent primary nitrate, nitrite,
silicate and phosphate standards for comparison with SIO/ODF primary
standards and made dilutions using glassware entirely independent of
the SIO/ODF glassware.

The results were as follows:

          Codispoti           SIO/ODF          
Nitrate   26.96 micromolar    26.85 micromolar
Nitrite    2.90 "              2.86 "
Silicate  86.4  "             85.8  "
Phosphate  2.36 "              2.36  "

On TN043, the volumetric equipment used for making routine nitrate and
phosphate standards was checked against volumetric ware calibrated by
LAC. The average difference between these comparsions of mid-range
standards was + or - 0.2% for phosphate and + or -0.4% for nitrate.

Because nitrite values in the suboxic waters of the Arabian Sea can
attain values of approximately 6.5 micromolar and because our routine
standards contained 22.5 micromoles of nitrate and 2.5 micromoles of
nitrite, we kept track of the efficiency of the Cd column that
reduces nitrate to nitrite in the nitrate analysis.  The efficiencies
were all greater than 97.7%, except for station 10 (TN053010xx).
Nitrate data are not reported for casts TN05301001 to TN05301008
because of problems with the cadmium reduction column.  For the
remaining casts at this station, the Cd column effciciency was ~96.4%.
No corrections have been made for any errors in nitrate arising from
deviations in cadmium column efficiency. NOTE THAT THE FULL-SCALE
NITRITE RANGE FOR THIS CRUISE WAS 7 MICROMOLAR.

     The ammonium results are the least precise of all the nutrient
results.  On TN039, three primary standards were compared with
agreement of about plus or minus three per cent of the full-scale (5.0
micromolar) value. These standards may have agreed within the
precision of the method, but we found a significant salinity effect on
the ammonium results that might explain some of these differences
since the salinities of the comparison standards varied a bit.
Experiments on the first JGOFS Arabian Sea process study cruise
(TN043) suggested that the ammonium signal decreases by approximately
3.5% for a salinity increase of 1.00.  Comparisons of an independent
standard compared by LAC with the SIO standard on this cruise (TN043)
when corrected for salinity differences between the standards agreed
to ~ + -0.1% of the full-scale value.  The largest absolute difference
was 0.025 micromolar and the average difference was 0.013 micromolar
for six comparisons between 1-3 micromolar. Thus, the average
difference between these two independent standards was + -0.006
micromolar. Comparisons of independent high concentration ammonium
standards (~2.5 and 5.0 micromolar) prepared by LAC with SIO standards
during TN054 agreed to better than + - 1% for four out of the five
standards when corrected for a salinity effect of 4.5%/1.00S on that
cruise.  One standard agreed to only + - 2.5%, but we assume that this
was due to a dilution error.  We believe that the suite of ammonium
comparisons suggests no systematic differences arising from standards
and dilutions, as all of the differences are within the precison of
the ammonium analysis.  Our results tend to confirm the need to take
salinity differences between samples and standards into account when
calculating the final ammonium concentrations. THE AMMONIUM VALUES IN
THIS REPORT HAVE BEEN CORRECTED FOR THIS EFFECT. ON THE TN053 
CRUISE THE SALINITY EFFECT CORRECTION IS A 3% DECREASE IN SIGNAL FOR
A SALINITY INCREASE OF 1.00. The average salinity of the working
standards used to calibrate the ammonium method was ~34.35 for stations
TN053001-TN053012 (inclusive) and ~34.96 for the remainder of the
stations. The ammonium method has additional problems, such as
contamination of "baseline" water etc.  These problems can introduce
inaccuracies on the order 0.1 micromolar, so differences in ammonium
concentrations of less than ~ 0.1 micromolar should not be
over-interpreted.

Deployment-specific processing description

<pre>
Methods:

In general, the methods employed for the bottle salinity, Winkler
dissolved oxygen, and nutrient analyses did not differ significantly
from those described in the JGOFS protocols that were distributed in
June, 1994. Minor differences included the following: 1) Sea Bird CTD
systems and bottle carousels were employed (SBE-9+ underwater units,
SBE-11 deck units, SBE-32 carousels). These units represent a newer
generation of equipment than the units described in the JGOFS
protocols. 2) The weights of the salts used for primary standards for
dissolved oxygen and nutrients were not adjusted to an "in vacuo"
basis as suggested in the protocols. It is unlikely that this
departure from procedure would cause significant errors. Our
calculations suggest that the maximum differences arising from our
decision to not correct to an "in vacuo" basis would range from 0.02%
(oxygen standards) to 0.06%(ammonium standards). 3) The protocols
give one a choice of adjusting nutrient methods so that calibration
curves are strictly linear, or opting for more response and taking
into account non-linearities. We choose the latter method. 4) No
corrections were made for "carryover" between nutrient samples run on
the Technicon Autoanalyzer. Data from this cruise, suggest that
carryover effects in our nutrient analyses are generally less than ~2%
of the concentration difference between adjacent samples. Examination
of cases where more than one sample was taken from a depth at which
there was a significant increase in nutrient concentrations will help
the user determine the carryover effect for many individual casts. 5)
Calibration and re-calibration of volumetric ware were not exactly as
described in the JGOFS protocols, but this was largely compensated for
by comparing independent standards diluted with independent volumetric
ware, and by re-calibration of some of the volumetric ware after
cruises TN045 and TN050. WE HAVE NOT YET RECALIBRATED THE VOLUMETRIC
WARE USED DURING TN053. WE WILL UPDATE THE DATA IF RECALIBRATION
SUGGESTS A NEED TO DO THIS, BUT WE DO NOT EXPECT SIGNIFICANT CHANGES
6) Duplicate oxygen samples were not drawn from every Niskin or Go-Flo
bottle, but there were several comparisons of bottles tripped at the
same depth. 7) Azide was added to the Winkler oxygen pickling
reagents to destroy nitrite that can be present in relatively high
concentrations in the Arabian Sea. ON LEGS PRIOR TO THIS ONE, OXYGEN
STANDARDIZATIONS WERE RUN USING REAGENTS THAT DID NOT CONTAIN AZIDE,
BUT DISCUSSIONS AND TESTS SUGGESTED THAT IT WOULD BE BETTER TO
STANDARDIZE WITH AZIDE, DESPITE SOME CONFUSION IN THE LITERATURE ON
THIS MATTER. CONSEQUENTLY, WE SWITCHED PROCEDURES BEGINNING WITH THIS
LEG (TN053) AND USED REAGENTS CONTAINING AZIDE TO STANDARDIZE. OUR
TESTS SUGGEST THAT THE MAXIMUM CHANGE IN OXYGEN CONCENTRATIONS ARISING
FROM THIS CHANGE WOULD OCCUR AT THE HIGHEST OXYGEN CONCENTRATIONS AND
BE < ~0.01 ML/L.

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 Niskin
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 THE MID-POINT OF THE SAMPLING BOTTLES WAS ONE METER ABOVE
THE CTD SENSORS. THE DATA HAVE NOT BEEN CORRECTED FOR THIS ONE METER
OR 1.01 DECIBAR DIFFERENCE BETWEEN CTD SENSOR AND SAMPLING BOTTLE
POSITIONS.

Salinity:

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 recently
calibrated sensors on the Sea Bird CTD systems was usually better than
0.02 (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.

Dissolved oxygen:

The Winkler dissolved oxygen set-up was built and supplied by the
SIO/ODF group. This system is computer controlled and detects the
end-point photometrically. Temperature of the thiosulfate and
standard solutions is automatically monitored by this system. Checks
on cruises TN039 and TN043 between independent standards prepared with
independent volumetric ware gave agreement of +-0.02 per cent. A
similar check made during TN054 suggested agreement of better than
+-0.15 per cent. The linearity of the "Dosimat" automatic buret was
also checked during cruises TN043 and TN054 with good results.

Nutrients:

Note that the terminology used to describe nutrients has become
somewhat loose over the years and that silicate=silicic acid, and
phospate=reactive phosphorus.

Nutrient analyses were performed on a 5-channel Technicon II AA
system that was modified and provided by the SIO/ODF group.

In assessing the nutrient standard comparisons outlined below,
note that the full-scale ranges for nutrients were as follows:
Ammonium =0 to 5 micromolar
Nitrate =0 to 45 "
Nitrite =0 to 5 "
Phosphate =0 to 3.6"
Silicate =0 to 180 "

These ranges were arrived at after an Internet poll of PI's and were
selected to cover the full depth concentration range for the Arabian
Sea. Since, we found nitrite concentrations that exceeded 5 micromolar
on several occasions, the nitrite concentration range was expanded
to 0-7 micromolar on leg TN050.

On the set-up and calibration cruise (TN039), the SIO/ODF nitrate and
nitrite standards and standards from the National Institute of
Oceanography in India (provided by S.W.A. Naqvi) were compared with
the following results:

NIO Nitrate Std.= 22.6 micromolar; SIO/ODF=22.5 micromolar
NIO Nitrite Std.= 2.42 micromolar; SIO/ODF = 2.50 micromolar
As can be inferred from the above, the nitrate plus nitrite
values were almost identical in the mixed standards;
25.02 (NIO) vs 25.00 (SIO)micromolar.

On TN039, Lou Codispoti prepared independent primary nitrate, nitrite,
silicate and phosphate standards for comparison with SIO/ODF primary
standards and made dilutions using glassware entirely independent of
the SIO/ODF glassware.

The results were as follows:

Codispoti SIO/ODF
Nitrate 26.96 micromolar 26.85 micromolar
Nitrite 2.90 " 2.86 "
Silicate 86.4 " 85.8 "
Phosphate 2.36 " 2.36 "

On TN043, the volumetric equipment used for making routine nitrate and
phosphate standards was checked against volumetric ware calibrated by
LAC. The average difference between these comparsions of mid-range
standards was + or - 0.2% for phosphate and + or -0.4% for nitrate.

Because nitrite values in the suboxic waters of the Arabian Sea can
attain values of approximately 6.5 micromolar and because our routine
standards contained 22.5 micromoles of nitrate and 2.5 micromoles of
nitrite, we kept track of the efficiency of the Cd column that
reduces nitrate to nitrite in the nitrate analysis. The efficiencies
were all greater than 97.7%, except for station 10 (TN053010xx).
Nitrate data are not reported for casts TN05301001 to TN05301008
because of problems with the cadmium reduction column. For the
remaining casts at this station, the Cd column effciciency was ~96.4%.
No corrections have been made for any errors in nitrate arising from
deviations in cadmium column efficiency. NOTE THAT THE FULL-SCALE
NITRITE RANGE FOR THIS CRUISE WAS 7 MICROMOLAR.

The ammonium results are the least precise of all the nutrient
results. On TN039, three primary standards were compared with
agreement of about plus or minus three per cent of the full-scale (5.0
micromolar) value. These standards may have agreed within the
precision of the method, but we found a significant salinity effect on
the ammonium results that might explain some of these differences
since the salinities of the comparison standards varied a bit.
Experiments on the first JGOFS Arabian Sea process study cruise
(TN043) suggested that the ammonium signal decreases by approximately
3.5% for a salinity increase of 1.00. Comparisons of an independent
standard compared by LAC with the SIO standard on this cruise (TN043)
when corrected for salinity differences between the standards agreed
to ~ + -0.1% of the full-scale value. The largest absolute difference
was 0.025 micromolar and the average difference was 0.013 micromolar
for six comparisons between 1-3 micromolar. Thus, the average
difference between these two independent standards was + -0.006
micromolar. Comparisons of independent high concentration ammonium
standards (~2.5 and 5.0 micromolar) prepared by LAC with SIO standards
during TN054 agreed to better than + - 1% for four out of the five
standards when corrected for a salinity effect of 4.5%/1.00S on that
cruise. One standard agreed to only + - 2.5%, but we assume that this
was due to a dilution error. We believe that the suite of ammonium
comparisons suggests no systematic differences arising from standards
and dilutions, as all of the differences are within the precison of
the ammonium analysis. Our results tend to confirm the need to take
salinity differences between samples and standards into account when
calculating the final ammonium concentrations. THE AMMONIUM VALUES IN
THIS REPORT HAVE BEEN CORRECTED FOR THIS EFFECT. ON THIS CRUISE
(TN053) THE SALINITY EFFECT CORRECTION IS A 3% DECREASE IN SIGNAL FOR
A SALINITY INCREASE OF 1.00. The average salinity of the working
standards used to calibrate the ammonium method was ~34.35 for stations
TN053001-TN053012 (inclusive) and ~34.96 for the remainder of the
stations. The ammonium method has additional problems, such as
contamination of "baseline" water etc. These problems can introduce
inaccuracies on the order 0.1 micromolar, so differences in ammonium
concentrations of less than ~ 0.1 micromolar should not be
over-interpreted.
</pre>

More information about this dataset deployment

Funding

Award Number	Funding Source
unknown Arabian Sea NSF	National Science Foundation

Instruments

Niskin bottle

Supplied Name: Niskin Bottle

Supplied Description:

10-liter Niskin type bottle

Instrument Type

Generic Name: Niskin bottle

Community Identifier: http://vocab.nerc.ac.uk/collection/L22/current/TOOL0412/

Generic Description:

A Niskin bottle (a next generation water sampler based on the Nansen bottle) is a cylindrical, non-metallic water collection device with stoppers at both ends. The bottles can be attached individually on a hydrowire or deployed in 12, 24, or 36 bottle Rosette systems mounted on a frame and combined with a CTD. Niskin bottles are used to collect discrete water samples for a range of measurements including pigments, nutrients, plankton, etc.

Parameters

Supplied Name	Supplied description	Supplied Units	Standard Name
event	a unique number assigned to each sampling operation consisting of month MM, day DD and time TT.T		event
sta	station number		sta
cast	CTD cast number		cast
date	date (YYYYMMDD) decoded as follows YYYY = year, MM = month, DD = day Date converted to UTC(GMT).		date
time	time of day in UTC(GMT)	decimal hours	time
lat	latitude (negative = South)	decimal degrees	lat
lon	longitude (negative = West)	decimal degrees	lon
bot	CTD rosette bottle number		bot
press	sample depth reported as pressure	decibars	press
temp	temperature, taken from CTD, IPTS-68	degrees C	temp
sal_bot	bottle salinity (Autosal; PSU)	dimensionless	sal_bot
O2_ml_L	oxygen (Winkler)	milliliters/liter	O2_ml_L
O2_umol_kg	oxygen (Winkler)	micromoles/kilogram	O2_umol_kg
O2_umol_L	oxygen (Winkler)	micromoles/liter	O2_umol_L
O2_4	oxygen (colorimetric)	milliliters/liter	no_bcodmo_term
NO3	nitrate	micromoles/liter	NO3
PO4	phosphate (reactive phosphorus)	micromoles/liter	PO4
SiO4	silicate (silicic acid/reactive silica)	micromoles/liter	SiO4
NO2	nitrite	micromoles/liter	NO2
NH4	ammonium	micromoles/liter	NH4
sta_std	Arabian Sea standard station identifier		sta_std
time_begin	start time of cast in UTC(GMT)	decimal hours	time_begin
time_end	end time of cast in UTC(GMT)	decimal hours	time_end
lat_begin	start latitude of cast (negative = South)	decimal degrees	lat_begin
lon_begin	start longitude of cast (negative = West)	decimal degrees	lon_begin
lat_end	end latitude of cast	decimal degrees	lat_end
lon_end	end longitude of cast	decimal degrees	lon_end
depth	depth calculated from pressure	meters	depth
sal_ctd	CTD salinity (PSS-78) when bottle tripped	dimensionless	sal_ctd

Database

Contribute Data

Dataset: bottle
Deployment: TT053

Dataset acquisition description

Final Corrections to Arabian Sea Niskin Bottle Data

performed at US JGOFS DMO October 28, 1996

US JGOFS Data Management Office Note Regarding Calculated Depth

Deployment-specific acquisition description

US JGOFS Arabian Sea Cruise: TN053 HYDROGRAPHIC BOTTLE DATA

Final Corrections

performed at US JGOFS DMO October 28, 1996

Dataset Processing Description

Deployment-specific processing description

Database

Contribute Data

Dataset: bottleDeployment: TT053

Dataset acquisition description

Final Corrections to Arabian Sea Niskin Bottle Data

performed at US JGOFS DMO October 28, 1996

US JGOFS Data Management Office Note Regarding Calculated Depth

Deployment-specific acquisition description

US JGOFS Arabian Sea Cruise: TN053 HYDROGRAPHIC BOTTLE DATA

Final Corrections

performed at US JGOFS DMO October 28, 1996

Dataset Processing Description

Deployment-specific processing description

Dataset: bottle
Deployment: TT053