Dataset: winter nitrate isotopes - hydrocast

Name: Wintertime nitrate delta 15N and delta 18O from hydrocasts from R/V S. A. Agulhas II cruise VOY03 in the Southern Ocean south of Africa in 2012 (Diatom-bound_N_Isotopes project)
Published: 2015-05-05
Keywords: oceans

Cite This Dataset

Spatial Extent: N:-34.578 E:14.176 S:-57.764 W:-0.045

Project:

High-resolution, Assemblage-specific Records of Diatom-bound N Isotopes from the Indian Sector of the Antarctic Ocean (Diatom-bound_N_Isotopes)

Principal Investigator:

Daniel M. Sigman (Princeton University)

Contact:

Sandi M. Smart (Stellenbosch University)

BCO-DMO Data Manager:

Shannon Rauch (Woods Hole Oceanographic Institution, WHOI BCO-DMO)

Version:

05 May 2015

Version Date:

2015-05-05

Validated:

Yes

Current State:

Final no updates expected

Wintertime nitrate delta 15N and delta 18O from hydrocasts from R/V S. A. Agulhas II cruise VOY03 in the Southern Ocean south of Africa in 2012 (Diatom-bound_N_Isotopes project)

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Description

Wintertime nitrate delta 15N and delta 18O from the Southern Ocean south of Africa from hydrocasts taken on the July 2012 R/V S.A. Agulhas II VOY03 expedition. The dataset includes hydrocast (depth-profile) data along with the hydrographic data accompanying each CTD.

Note: In addition to the awards identified below, the dataset was also supported by funding from the South African National Research Foundation (NRF), Applied Centre for Climate and Earth Systems Science (ACCESS), University of Cape Town (UCT), and the Grand Challenges Program of Princeton University.

Methods & Sampling

Samples were collected aboard the R/V S.A. Agulhas II and analyzed in the Sigman lab at Princeton University using the "denitrifier method" to convert sample nitrate to N2O gas. The isotopic composition of N2O was measured by GC-IRMS using a Thermo MAT 253 mass spectrometer with a purpose-built on-line N2O extraction and purification system. For the nitrate+nitrite data, the pooled sample standard deviation is 0.05‰ for delta 15N (n = 3-7) and 0.17‰ for delta 18O (n = 3-5). For the ‘nitrate-only’ data, the pooled sample standard deviation is 0.05‰ for delta 15N (n = 3-7) and 0.13‰ for delta 18O (n = 3-7). See methods section of Smart et al. (2015) for details of sample collection, isotope analysis and data quality.

Related Publications:
Smart, S.M., S.E. Fawcett, S.J. Thomalla, M.A. Weigand, C.J.C. Reason, and D.M. Sigman. 2015. Isotopic evidence for nitrification in the Antarctic winter mixed layer, Global Biogeochem. Cycles, 29, doi: 10.1002/2014GB005013.

Data Processing Description

Individual sample analyses were referenced against automated injections of N2O from a gas cylinder; however, the N2O cylinder is not used as the absolute reference. Rather, each sample run included replicates of two international reference materials, IAEA-N3 and USGS-34 that were used to calibrate isotope ratios to that of N2 in air (for delta 15N) and VSMOW (for delta 18O). An in-house N2O standard was also run with each batch of samples to monitor mass spectrometry. See methods section of Smart et al. (2015) for a description of the procedures followed.

BCO-DMO Processing Notes:
- Modified parameter names to conform with BCO-DMO naming conventions.
- Replaced blanks (missing data) with 'nd', meaning 'no data'.

Data Files

File
hydrocast.csv (Comma Separated Values (.csv), 36.65 KB) MD5:4df4d76bfc615a85ffd1bc3ae7fd35b5 Primary data file for dataset ID 557616

More Information about this dataset

Funding Sources

Funding Source	Award Number
NSF Division of Polar Programs	PLR-1401489
NSF Division of Polar Programs	PLR-0612198
NSF Division of Ocean Sciences	OCE-1136345
NSF Division of Ocean Sciences	OCE-1060947
European Commission Seventh Framework Programme	FP7 265294

Deployments

Deployment	Synonyms	Start Date	Platform	Investigator
VOY03		2012-07-10	R/V S.A. Agulhas II		data info

Instruments

CTD Sea-Bird

Supplied Name: CTD

Supplied Description:

Circumpolar fronts were identified from surface and subsurface (200m) temperature and salinity properties using data obtained from a Sea-Bird conductivity-temperature-depth (CTD) sensor mounted on the Niskin bottle rosette, as well as
from 28 underway-CTD and 88 expendable bathythermograph deployments.

Instrument Type

Generic Name: CTD Sea-Bird

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/130/

Generic Description:

Conductivity, Temperature, Depth (CTD) sensor package from SeaBird Electronics, no specific unit identified. This instrument designation is used when specific make and model are not known. See also other SeaBird instruments listed under CTD. More information from Sea-Bird Electronics.

Niskin bottle

Supplied Description:

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.

Sea-Bird SBE 43 Dissolved Oxygen Sensor

Supplied Name: Sea-Bird SBE 43

Supplied Description:

Dissolved oxygen profiles (obtained for every CTD cast from a mounted Sea-Bird SBE 43 sensor) were used together with potential density, salinity, and nitrate profiles to identify key water masses.

Instrument Type

Generic Name: Sea-Bird SBE 43 Dissolved Oxygen Sensor

Acronym: SBE-43 DO

Community Identifier: http://vocab.nerc.ac.uk/collection/L22/current/TOOL0036/

Generic Description:

The Sea-Bird SBE 43 dissolved oxygen sensor is a redesign of the Clark polarographic membrane type of dissolved oxygen sensors. more information from Sea-Bird Electronics

Parameters

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

Supplied Name	Supplied description	Supplied Units	Standard Name
station	Station number.	dimensionless	station
date	Month, day, and year of sampling.	mm/dd/yy	date
time	Time, in hours and minutes, of sampling.	HHMM	time
lat	Latitude in decimal degrees North. (Negative values = South).	decimal degrees	lat
lon	Longitude in decimal degrees East.	decimal degrees	lon
depth_mixed_layer	Mixed layer calculated from sigma-t using ref depth = 32 m. Mixed layer depth at each station is defined as the closest depth to the surface at which sigma theta is greater by >= 0.03 kg m-3 than the value at a reference depth of 32 m (the shallowest depth common to every CTD station) (based on the criterion of de Boyer Montégut et al. (2004)).	meters	depth_mixed_layer
sample	Sample ID number.	dimensionless	sample
depth	Sample depth.	meters	depth
temp	Water temperature.	degrees Celsius ( C)	temp
sal	Salinity.	practical salinity units (psu)	sal
oxygen_corr	Oxygen (corrected).	milliliters per liter (ml/l)	O2_ml_L
sigma_t	Potential density (sigma-theta); calculated from temperature and salinity.	kilograms per cubic meter (kg/m^3)	sigma_t
NO3_NO2_mean	Mean nitrate (NO3) plus nitrite (NO2) concentration of a sample in micromolar units.	micromolar (uM)	NO3_NO2
NO3_NO2_stdev	Standard deviation of the nitrate (NO3) plus nitrite (NO2) concentration of a sample in micromolar units.	micromolar (uM)	std_dev
d15N_NO3_NO2_mean	delta 15N of NO3+NO2. d15N (‰ vs. AIR) is the nitrogen isotopic composition of a sample expressed in delta notation (in units of per mil) relative to atmospheric N2, where delta 15N = {[ (15N/14N)sample / (15N/14N)atmN2 ] – 1} × 1000.	per mil	no_bcodmo_term
d15N_NO3_NO2_stdev	Standard deviation of d15N_NO3_NO2_mean.	per mil	std_dev
d18Ocorr_NO3_NO2_mean	delta 18O of NO3+NO2. d18O (‰ vs. VSMOW) is the oxygen isotopic composition of a sample expressed in delta notation (in units of per mil) relative to Vienna Standard Mean Ocean Water (VSMOW), where delta 18O = {[ (18O/16O)sample / (18O/16O)VSMOW ] – 1} × 1000.	per mil	no_bcodmo_term
d18O_NO3_NO2_stdev	Standard deviation of d18O_NO3_NO2_mean.	per mil	std_dev
NO3_mean	Mean nitrate (NO3) concentration of a sample in micromolar units, measured after nitrite (NO2) had been removed (using the protocol of Granger and Sigman (2009)).	micromolar (uM)	NO3
NO3_stdev	Standard deviation of the nitrate (NO3) concentration of a sample in micromolar units, measured after nitrite (NO2) had been removed (using the protocol of Granger and Sigman (2009)).	micromolar (uM)	std_dev
d15N_NO3_mean	delta 15N of NO3. d15N (‰ vs. AIR) is the nitrogen isotopic composition of a sample expressed in delta notation (in units of per mil) relative to atmospheric N2, where delta 15N = {[ (15N/14N)sample / (15N/14N)atmN2 ] – 1} × 1000.	per mil	dN15_NO3
d15N_NO3_stdev	Standard deviation of d15N_NO3_mean.	per mil	std_dev
d18O_NO3_mean	delta 18O of NO3. d18O (‰ vs. VSMOW) is the oxygen isotopic composition of a sample expressed in delta notation (in units of per mil) relative to Vienna Standard Mean Ocean Water (VSMOW), where delta 18O = {[ (18O/16O)sample / (18O/16O)VSMOW ] – 1} × 1000.	per mil	d18O_NO3
d18O_NO3_stdev	Standard deviation of d18O_NO3_mean.	per mil	std_dev
month	2-digit month of year.	mm (01 to 12)	month
day	2-digit day of month.	dd (01 to 31)	day
year	4-digit year.	YYYY	year
ISO_DateTime_UTC	Date and time (UTC) formatted to ISO 8601 standard, where T indicates the start of the time string and Z indicates UTC.	YYYY-mm-ddTHH:MM:SS.xxZ	ISO_DateTime_UTC

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Dataset: winter nitrate isotopes - hydrocast