N2 gas concentration in excess of saturation determined by N2:Ar ratiometry from samples collected in the Bering Sea, Chukchi Sea, and Western Arctic on cruise HLY1702 from August to September 2017

Website: https://www.bco-dmo.org/dataset/812052
Data Type: Cruise Results
Version: 1
Version Date: 2020-05-20

Project
» Collaborative Research: GEOTRACES Arctic Ocean section-Constraining Nitrogen Cycling in the western Arctic Ocean. (US GEOTRACES Arctic Nitrogen Flux)
ContributorsAffiliationRole
Altabet, Mark A.University of Massachusetts Dartmouth (UMASSD-SMAST)Principal Investigator
Rauch, ShannonWoods Hole Oceanographic Institution (WHOI BCO-DMO)BCO-DMO Data Manager

Abstract
N2 gas concentration in excess of saturation determined by N2:Ar ratiometry from samples collected in the Bering Sea, Chukchi Sea, and Western Arctic on cruise HLY1702 from August to September 2017.


Coverage

Spatial Extent: N:73.56 E:-157.152317 S:62.39 W:-174.574833
Temporal Extent: 2017-08-29 - 2017-09-12

Dataset Description

N2 gas concentration in excess of saturation determined by N2:Ar ratiometry.


Acquisition Description

Sampling at sea was done using a standard SeaBird CTD/Rosette system. Hydrographic data processing used SeaBird software and standard procedures.

N2 excess was determined from N2/Ar ratios measured using procedures described by Charoenpong et al. (2014) with an IsoPrime Isotope Ratio Mass Spectrometer (IRMS) using IonVantage software.

Final data reduction and organization was done using Microsoft Excel.


Processing Description

BCO-DMO Processing:
- renamed fields;
- changed date format to yyyy-mm-dd from mm/dd/yy;
- changed #N/A to nd ("no data").


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Related Publications

Charoenpong, C. N., Bristow, L. A., & Altabet, M. A. (2014). A continuous flow isotope ratio mass spectrometry method for high precision determination of dissolved gas ratios and isotopic composition. Limnology and Oceanography: Methods, 12(5), 323–337. doi:10.4319/lom.2014.12.323
Methods

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Parameters

ParameterDescriptionUnits
StationStation number unitless
NiskinNiskin bottle number unitless
LatLatitude degrees North
LonLongitude degrees East
DateDate; format: yyyy-mm-dd unitless
DepthDepth meters (m)
TempTemperature degrees Celsius
SalinitySalinity unitless
Sigma_ThetaSigma theta density kg/m3 -1000
excess_N2Excess N2 umol/kg
excess_N2_stdevStandard deviation of replicate measurements umol/kg


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Instruments

Dataset-specific Instrument Name
SeaBird CTD/Rosette
Generic Instrument Name
CTD Sea-Bird
Generic Instrument 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.

Dataset-specific Instrument Name
IsoPrime Isotope Ratio Mass Spectrometer (IRMS)
Generic Instrument Name
Isotope-ratio Mass Spectrometer
Generic Instrument Description
The Isotope-ratio Mass Spectrometer is a particular type of mass spectrometer used to measure the relative abundance of isotopes in a given sample (e.g. VG Prism II Isotope Ratio Mass-Spectrometer).


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Deployments

HLY1702

Website
Platform
USCGC Healy
Start Date
2017-08-26
End Date
2017-09-14
Description
See cruise information from Rolling Deck to Repository (R2R): https://www.rvdata.us/search/cruise/HLY1702


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Project Information

Collaborative Research: GEOTRACES Arctic Ocean section-Constraining Nitrogen Cycling in the western Arctic Ocean. (US GEOTRACES Arctic Nitrogen Flux)

Coverage: Chukchi shelf and western Arctic Ocean basins


In this project, a group of investigators from the University of Connecticut, the University of Massachusetts-Dartmouth, and Brown University will participate in the 2015 U.S. GEOTRACES Arctic expedition to determine the biogeochemistry of nitrogen in the region. In common with other multinational initiatives in the International GEOTRACES Program, the goals of the U.S. Arctic expedition are to identify processes and quantify fluxes that control the distributions of key trace elements and isotopes in the ocean, and to establish the sensitivity of these distributions to changing environmental conditions. Some trace elements are essential to life, others are known biological toxins, and still others are important because they can be used as tracers of a variety of physical, chemical, and biological processes in the sea. Nitrogen is one of the two major nutrients required universally by plankton in the ocean, and this study in the Arctic Ocean will increase our understanding of the ocean?s ecology, productivity, and carbon cycle. This study will also provide training for graduate and undergraduate students, and results will be shared through public outreach events.

The state of knowledge of Arctic nitrogen (N) biogeochemistry remains cursory as compared to that in other ocean basins despite the fact that understanding Arctic Ocean nitrogen cycling is central to understanding its global biogeochemistry. For one, benthic nitrogen loss on Arctic continental shelves may represent a globally significant sink of oceanic fixed nitrogen. Second, benthic nitrogen loss on the Arctic continental shelf and slope reduces the ratio of nitrate to phosphate substantially below the mean requirements of phytoplankton nitrogen, consequently limiting primary production at the ice-free surface of the western Arctic Ocean. In light of the rapid changes in Arctic climatology, the characterization of its biogeochemistry and establishment of a baseline from which to monitor future changes is critical. Researchers will use the stable N isotope (15N/14N) ratio in nitrate, nitrite, ammonium, and nitrogen gas determined for a suite of dissolved, particulate, atmospheric, snow, and sea-ice samples to better constrain the spatial and temporal variability of biological nitrogen transformations in the Arctic. Results from this study will provide a first order understanding of the contribution of water masses to the regional nitrogen budget, identify regional nitrogen sources and sinks, and diagnose important biological nitrogen transformations that occur on the Chukchi shelf, and in the central basins.



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Funding

Funding SourceAward
NSF Division of Ocean Sciences (NSF OCE)

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