Dataset: O2 Underway

Name: Oxygen from underway system from NOAA Ship Ronald H. Brown cruise RB-08-02 in the Southwest Atlantic sector of the Southern Ocean near South Georgia Island in 2008 (SO_GasEx project)
Published: 2009-06-19
Keywords: oceans

Cite This Dataset

Spatial Extent: N:-35.556 E:-36.117 S:-53.753 W:-55.769

Project:

Southern Ocean Gas Exchange Experiment (SO_GasEx)

Program:

Ocean Carbon and Biogeochemistry (OCB)

United States Surface Ocean Lower Atmosphere Study (U.S. SOLAS)

Principal Investigator:

Roberta C. Hamme (University of Victoria, UVic)

Contact:

Burke Hales (Oregon State University, OSU-CEOAS)

BCO-DMO Data Manager:

Stephen R. Gegg (Woods Hole Oceanographic Institution, WHOI)

Version:

26 July 2010

Version Date:

2009-06-19

Validated:

Yes

Current State:

Final no updates expected

Oxygen from underway system from NOAA Ship Ronald H. Brown cruise RB-08-02 in the Southwest Atlantic sector of the Southern Ocean near South Georgia Island in 2008 (SO_GasEx project)

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Description

SO-GasEx Final Discrete Oxygen Data from underway system analyzed by Winkler Titration

Methods & Sampling

Operation description:
Discrete analysis of dissolved oxygen on ship's underway seawater line.

Sampling times and locations:
Sampled all CTD casts where Niskin bottles were tripped and two pumped casts.
One deep cast to 4600m, three mid-depth casts to 1500m, other casts usually to 500m or 100m.
See CTD cast logs and bottle files for specific times, locations, and flask numbers for each cast.

Overall sampling strategy:
Normally collected one sample from each unique depth.
If multiple Niskins were tripped at a given depth, hydrography sampled only one of these.
Duplicate samples collected on two Niskins per cast, usually near the O2 minimum and just under the mixed layer.
A mixture of triplicates and duplicates were collected from the underway seawater line.

Sample collection:
Roberta Hamme collected most of the oxygen samples.
However, on casts where noble gas samples or a profile of O2/N2/Ar samples were collected, Sarah Purkey collected the discrete oxygen samples.
No difference in precision was detected between the two samplers, as measured by the standard deviation of duplicate samples.

Data Processing Description

Analytical method:
Winkler titration method using Langdon amperometric detection of the endpoint.
Samples preserved with 1 mL each of MnCl2 and NaI-NaOH solutions.
Shaken twice and stored in dark with tap water around caps to form seal.
Precipitate dissolved with 1mL H2SO4 solution and titrated with thiosulfate solution.
Endpoint is detected via electrode current that is related to concentration of I3-.
Normally run within 24 hours, but some samples from underway system sat for 2-3 days.
3-5 KIO3 standards run at beginning of each day running samples.
Blanks run in distilled water used for calculations.
Seawater blanks required 2-2.5 uL more titrant than distilled water blanks.

Calculations:
Final dataset calculated using distilled water blanks in keeping with official WOCE methodology.
High quality seawater blanks were determined on this cruise.
Data is likely of higher accuracy when calculated with seawater blanks.
To convert distilled blank numbers to seawater blank numbers, simply subtract 0.530 umol/kg (micromol/kg).
Saturations calculated relative to Garcia and Gordon (1992,1993) with no correction for atmospheric pressure variations.

BCO-DMO Processing Notes
- Generated from original file Winkler_SOGasEx_Underway.csv

BCO-DMO Edits
- date reformatted to YYYYMMDD
- Time reformatted to HHMM
- lon/lat padded to 3 decimal places
- Column headers/parameter names edited to conform to BCO-DMO convention (blanks replaced with underscores or eliminated)
- blank fields changed to 'nd'
- decimal places padded as appropriate for consistency

Comments from original text file - Winkler_SOGasEx_Underway.csv
Final Discrete Oxygen Data from underway system analyzed by Winkler Titration. SOGasEx cruise. Feb 29-April 11, 2008 aboard R/V Ron Brown.
This data is calculated with a distilled water blank. To obtain values calculated with a seawater blank, subtract 0.530 umol/kg.
Flag = 2 means good; Flag = 3 means questionable (unexplained high std dev); Flag = 4 means bad (see metadata file for explanation).

Data Files

File
O2_Underway.csv (Comma Separated Values (.csv), 6.71 KB) MD5:3f32277362389eaa86381183b3b53837 Primary data file for dataset ID 3139

More Information about this dataset

Funding Sources

Funding Source	Award Number
National Aeronautics & Space Administration	unknown SO_GasEx NASA
National Oceanic and Atmospheric Administration	unknown SO_GasEx NOAA
National Science Foundation	unknown SO_GasEx NSF

Deployments

Deployment	Synonyms	Start Date	Platform	Investigator
RB-08-02	RB0802 RHB_SO-GasEx	2008-02-29	NOAA Ship Ronald H. Brown	Christopher L. Sabine (Chief Scientist) David T. Ho (Co-Chief Scientist)	data info

Instruments

Oyxgen Titrator -Langdon

Supplied Name: Langdon Oyxgen Titrator

Supplied Description:

Instrument Type

Generic Name: Oyxgen Titrator -Langdon

Acronym: O2 titrator -Langdon

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/LAB12/

Generic Description:

A Langdon Oyxgen Titrator is an amperometric oxygen titration system developed to measure dissolved oxygen in seawater. The device uses a conventional polarographic electrode in connection with chronoamperometry to overcome many of the problems limiting the performance of oxygen electrodes. Reproducibility is typically better than +/- 0.8 micromolar and essentially drift-free for several weeks. A microcomputer controls all phases of the measuring process: pulse generation, data acquisition, reduction, and storage. Software is used to correct sensor output for temperature dependence and an activity coefficient, a function of temperature and salinity, is computed to correct for salinity. (Langdon, 1984. Deep Sea Research Part A. Oceanographic Research Papers, Volume 31, Issue 11, pp. 1357-1367; Culberson and Huang, 1987. Automated amperometric oxygen titration. Deep Sea Res. 34:875-880).

Parameters

Date and time formats are described in python strftime() syntax.

Supplied Name	Supplied description	Supplied Units	Standard Name
corrected_Salinity	Corrected Salinity	dimensionless	no_bcodmo_term
date	Date UTC	YYYYMMDD	date
Draw_T	Draw Temperature	degrees Celsius	no_bcodmo_term
event	Unique event number	YDAHHMM	event
Flag	Data quality flag Flag = 2 means good; Flag = 4 means bad	integer	flag
lat	latitude, negative denotes South	decimal degrees	lat
lon	longitude, negative denotes West	decimal degrees	lon
O2_conc	O2 concentration	micro moles/kilogram	O2
O2_sat	Percentage of O2 saturation	dimensionless	O2sat
pCO2_Salinity	pCO2 salinity	dimensionless	no_bcodmo_term
Sampling_Location	Description of sampling location on the vessel	text	no_bcodmo_term
Ships_T	Ship's Temperature (seawater??)	degrees Celsius	no_bcodmo_term
Std_dev	Standard of deviation	micro moles/kilogram	no_bcodmo_term
time	Time UTC	HHMM	time

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Dataset: O2 Underway