Metadata Report for BODC Series Reference Number 1978382

• Metadata Summary

• Problem Reports

• Data Access Policy

• Narrative Documents

• Project Information

• Data Activity or Cruise Information

• Fixed Station Information

• BODC Quality Flags

• SeaDataNet Quality Flags

Metadata Summary

Problem Reports

No Problem Report Found in the Database

Data Access Policy

Open Data supplied by Natural Environment Research Council (NERC)

You must always use the following attribution statement to acknowledge the source of the information: "Contains data supplied by Natural Environment Research Council."

Narrative Documents

VG IsoPrep 18 water equilibration device

A laboratory instrument which prepares water samples for isotopic analysis using a H₂O-CO₂ equilibration system. The instrument requires 3 ml of water for one measurement to be made. The IsoPrep 18 is usually coupled with an Isotope-Ratio Mass Spectrometer (IRMS) where the prepared gases are then ionised and analysed for their isotopic content.

Niskin Bottle

The Niskin bottle is a device used by oceanographers to collect subsurface seawater samples. It is a plastic bottle with caps and rubber seals at each end and is deployed with the caps held open, allowing free-flushing of the bottle as it moves through the water column.

Standard Niskin

The standard version of the bottle includes a plastic-coated metal spring or elastic cord running through the interior of the bottle that joins the two caps, and the caps are held open against the spring by plastic lanyards. When the bottle reaches the desired depth the lanyards are released by a pressure-actuated switch, command signal or messenger weight and the caps are forced shut and sealed, trapping the seawater sample.

Lever Action Niskin

The Lever Action Niskin Bottle differs from the standard version, in that the caps are held open during deployment by externally mounted stainless steel springs rather than an internal spring or cord. Lever Action Niskins are recommended for applications where a completely clear sample chamber is critical or for use in deep cold water.

Clean Sampling

A modified version of the standard Niskin bottle has been developed for clean sampling. This is teflon-coated and uses a latex cord to close the caps rather than a metal spring. The clean version of the Levered Action Niskin bottle is also teflon-coated and uses epoxy covered springs in place of the stainless steel springs. These bottles are specifically designed to minimise metal contamination when sampling trace metals.

Deployment

Bottles may be deployed singly clamped to a wire or in groups of up to 48 on a rosette. Standard bottles and Lever Action bottles have a capacity between 1.7 and 30 L. Reversing thermometers may be attached to a spring-loaded disk that rotates through 180° on bottle closure.

RRS James Clark Ross JR20141231 (JR307, JR308) CTD bottle Macronutrients, Total Nitrogen and Carbon, Dissolved Inorganic Carbon (DIC), Total Alkalinity (TA), Oxygen and Nitrogen isotopes

Originator's Protocol for Data Acquisition and Analysis

11 stations were sampled along a transect across the WAP shelf, from the mouth of the glacially-carved canyon Marguerite Trough, along this trough into Marguerite Bay and into Ryder Bay. At each station, a full-depth conductivity-temperature-depth (CTD) cast was taken and water samples were taken over the full water column depth on the upcast of CTD deployments from 12 L Niskin bottles mounted on the 24-bottle rosette.

Bottles were sampled for carbonate system parameters, immediately after the Niskin was opened, then macronutrients, isotopic composition of nitrate, particulate organic carbon (POC), particulate nitrogen (PN), oxygen isotopes of seawater.

• Carbonate chemistry: samples were drawn using tygon tubing into 500 ml borosilicate glass bottles where 100 µl saturated mercuric chloride solution was added; the samples were stored onboard and returned to the laboratory for analysis
• DIC and TA: analysis were conducted at Rothera Research Station using a VINDTA 3C Marianda following methods prescribed in Dickson et al. (2007). Determination of DIC was made through sample acidification with 8.5% H₃PO₄ and gas extraction with coulometric analysis (Johnson et al., 1987) and total alkalinity by automated potentiometric titration with 0.1 M hydrochloric acid (Dickson, 1981). Analyses of Certified Reference Material (CRM, batch 130) supplied by A.G. Dickson (Scripps Institute of Oceanography) every 20 samples ensured the instrument accuracy was better than 2 µmol kg^-1. The precision of the DIC and alkalinity measurements was 1.7 and 1.5 µmol kg^-1, respectively, based on the average difference between CRM in-bottle duplicate analyses (total of 54).
• Macronutrient and nitrate isotope parameters: samples were filtered using Acrodisc PF syringe filters with 0.2 µm Supor membranes, snap frozen at -80°C for 12 hours and then stored at -20°C for subsequent analysis in the UK. Prior to nutrient analysis, samples were thawed for 48 h to ensure complete redissolution of secondary silicate precipitates to silicic acid. Concentrations of nitrate+nitrite, nitrite, phosphate and silicic acid were analysed using a Technicon AAII segmented flow autoanalysis system with reference materials from General Environmental Technos Co. (Japan) at Plymouth Marine Laboratory, UK. Raw data were corrected to elemental standards and ambient ocean salinity and pH. Samples were assayed in duplicate and standard deviation was generally better than 0.2 µmol L^-1 for nitrate+nitrite, 0.01 µmol L^-1 for nitrite, 0.02 µmol L^-1 for phosphate and 0.6 µmol L^-1 for silicic acid. Measured concentrations of nitrate+nitrite are reported here as nitrate, as the contribution of nitrite to the nitrate+nitrite pool is low (< 3%)
• Stable isotope of nitrogen and oxygen in nitrate: analysis was performed at the University of Edinburgh using the bacterial denitrifier method and gas chromatography isotope ratio mass spectrometry (GC-IRMS) [Casciotti et al., 2002; McIlvin and Casciotti, 2011; Sigman et al., 2001; Weigand et al., 2016]. Briefly, denitrifying bacteria (Pseudomonas aureofaciens) were grown on agar plates and in tryptic soy broth (30 g l^-1 milli-Q water) amended with sodium nitrate (1 g l^-1), ammonium sulphate (0.25 g l^-1) and potassium phosphate monobasic (5 g l^-1), and used for the quantitative conversion of sample nitrate to N₂O gas. Bacteria were isolated from tryptic soy broth by centrifugation after 6 to 8 days and resuspended in nitrate-free media, 3 ml aliquots of which were purged with N2 gas for three hours before being injected with seawater sample volumes to provide 20 nmol of nitrate. After denitrification overnight, NaOH was added to samples to lyse bacterial cells and scavenge CO₂. Sample N₂O was analysed using a Thermo Finnigan DeltaPlus Advantage mass spectrometer with a CTC Analytics GC Pal autosampler and a Thermo Finnigan Gas Bench II gas preparation system. Results are presented in the delta per mille notation relative to international standards atmospheric N₂ for N (δ15NNO3 ‰AIR) and Vienna Standard Mean Ocean Water (VSMOW) for O (δ18ONO3 ‰VSMOW), after raw sample data were referenced to IAEA-NO3 and USGS-34 standards. Analytical precision was around 0.2 ‰ for N and around 0.3 ‰ for O. δ18ONO3 was corrected for fractionation during conversion of nitrate to N₂O, for exchange with seawater oxygen during denitrification, and for blanks using the correction scheme of the Sigman Laboratory, Princeton University [Weigand et al., 2016]. Nitrite was not removed prior to denitrification. However, δ15NNO3 values were corrected for nitrite interference using measured concentrations of nitrite and nitrate+nitrite and published values for δ15NNO2 of -24 ‰ for samples >= 100 m depth and -69 ‰ for samples < 100 m [Kemeny et al., 2016]. These corrections are similar to those detailed in Henley et al. [2017], except the δ15NNO2 value used here for upper ocean samples is significantly lower than in the previous study (-24 ‰). δ18ONO3 data were not corrected for nitrite interference
• Particulate Organic Carbon (POC) and Nitrogen (PN): samples were filtered through muffle-furnaced 25 mm ~0.7 µm GF/F filters using a custom-built overpressure system. Filters were dried overnight, snap frozen at -80°C and stored at -20°C for analysis at the University of Edinburgh. Similar to Henley et al. [2012], samples were decarbonated prior to analysis by rewetting with milli-Q water and fuming with 50% HCl for 24 hours and then dried at 50°C overnight. Analysis was done using a Carlo Erba NA 2500 elemental analyser in-line with a VG Prism III IRMS. Isotopic data were referenced to Vienna Pee Dee Belemnite (‰VPDB) for δ13CPOC and atmospheric N₂ (‰_AIR) for δ15NPN using PACS isotopic reference material. POC and PN concentrations were calibrated to an acetanilide elemental standard. Analytical precision was around 0.2‰
• Stable oxygen isotopes: samples were taken directly from the Niskin into 50 ml glass bottles, which were immediately sealed with stoppers and crimp caps. These were stored in the dark at room temperature during transport to the UK, where they were analysed at the British Geological Survey, Keyworth. Samples were run on a VG Isoprep 18 and SIRA 10 mass spectrometer, with duplicate analyses indicating a precision better than 0.02 ‰, and δ18O data being standardised relative to VSMOW. The δ18O and salinity data are used here in a simple 3-endmember mass balance that quantifies separately the contributions to the freshwater budget of each sample from sea ice melt and meteoric water (the sum of glacial discharge and direct precipitation). This was developed originally for the Arctic [Ostlund and Hut, 1984], and was used most recently at the WAP by Meredith et al. [2017], which presents full details on the procedure

References Cited

Dickson AG and Millero FJ, 1987. A comparison of the equilibrium constants for the dissociation of carbonic acid in seawater media, Deep Sea Research Part A, Oceanographic Research Papers, vol. 34, no. 10, 1733-1743. DOI: 10.1016/0198-0149(87)90021-5

Henley S. F., Annett A. L., Ganeshram R. S., Carson D. S., Weston K., Crosta X., Tait A., Dougans J., Fallick A. E., and Clarke A., 2012. Factors influencing the stable carbon isotopic composition of suspended and sinking organic matter in the coastal Antarctic sea ice environment, Biogeosciences, 9, 1137-1157, DOI: 10.5194/bg-9-1137-2012

Lewis, E., Wallace, D.W.R. and J. Allison, L. (1998). CO2SYS-Program developed for CO2 system calculations. Carbon Dioxide Inf. Anal. Centre. DOI: 10.2172/639712.

Meredith Michael P., Stammerjohn Sharon E., Venables Hugh J., Ducklow Hugh W., Martinson Douglas G., Iannuzzi Richard A., Leng Melanie J., van Wessem Jan Melchior, Reijmer Carleen H., Barrand Nicholas E., 2017., Changing distributions of sea ice melt and meteoric water west of the Antarctic Peninsula, Deep Sea Research Part II: Topical Studies in Oceanography, Volume 139, 40-57, DOI: https://doi.org/10.1016/j.dsr2.2016.04.019

Östlund H. G., and G. Hut, 1984. Arctic Ocean water mass balance from isotope data, J. Geophys. Res., 89(C4), 6373-6381, DOI: 10.1029/JC089iC04p06373.

van Heuven S, Pierrot D, Rae JWB, Lewis E and Wallace DWR, 2011. CO2SYS v 1.1: MATLAB Program Developed for CO2 System Calculations. ORNL/CDIAC-105b., Software, Oak Ridge National Laboratory, Oak Ridge, Tennesee. DOI: 10.3334/CDIAC/otg.CO2SYS_MATLAB_v1.1

Venables Hugh J., Meredith Michael P., Brearley J. Alexander, 2017. Modification of deep waters in Marguerite Bay, western Antarctic Peninsula, caused by topographic overflows. Deep Sea Research II: Topical Studies in Oceanography, (139), 9-17. DOI: 10.1016/j.dsr2.2016.09.005

Instrumentation Description

• DIC and TA: VINDTA 3C Marianda
• Macronutrient and nitrate isotope: Technicon AAII segmented flow autoanalysis system
• Stable isotope composition of nitrogen and oxygen: gas chromatography isotope ratio mass spectrometry
• POC and PN: Carlo Erba NA 2500 elemental analyser in-line with a VG Prism III IRMS
• Stable Oxygen isotopes: VG Isoprep 18 and SIRA 10 mass spectrometer

BODC Data Processing Procedures

The data were received in an excel spreadsheet accompanied with metadata (year, month, day, hour, minute, latitude, longitude, station, sampleid, cast, niskin and depth). Originator's DIC and TA data were sent with WOCE quality control flags. Following BODC's standard procedures, these flags were matched to BODC flags according to the table below:

The originator's file also contained data for file pCO₂ and ph which were not ingested as they were derived from DIC and TA, using in situ temperature, salinity and nutrient concentrations (all included in the file). No unit conversions were applied as originator's units were equivalent to the units used in the BODC parameter codes. The originator's file is available upon request.

The originator's metadata were matched against BODC records and no discrepancies were found. The parameters were mapped against BODC's vocabulary;

Project Information

NE/K010034/1 Isotopic characterisation of nutrient dynamics and Upper Circumpolar Deep Water behaviour in the West Antarctic Peninsula sea ice environment

Introduction

Solo NERC funded grant, 'isotopic characterisation of nutrient dynamics and Upper Circumpolar Deep Water (UCDW) behaviour in the West Antarctic Peninsula sea ice environment' with grant reference NE/K010034/1. The project is led by Dr Sian Henley (University of Edinburgh, School of Geosciences).

Background and Objectives

The research project aims to examine ways in which ongoing climate change and sea ice decline at the West Antarctic Peninsula (WAP) are influencing nutrient budgets and biogeochemical cycling throughout the region. The WAP is an ecologically important region of high primary productivity, where nutrient cycling is known to be crucial to phytoplankton production and its relationship with carbon dioxide dynamics. The study comprises of three components:

• A time-series study over three austral summer growing seasons in Ryder Bay, WAP, to examine temporal changes in fixed nitrogen budgets and cycling, in relation to inter-annual variability in sea ice, water column structure and productivity.
• A ship-based transect from the shelf break to Marguerite Bay to examine deep-water behaviour and its impact on the supply of nutrients to high productivity coastal regions.
• Ship-based sampling across the wider WAP shelf region to examine spatial variability in nutrient dynamics, productivity, sea ice and physical oceanography, and give a broader context to the time-series study.

Fieldwork

Ship based sampling was completed on-board RRS James Clark Ross cruise JR20141231 (JR307, JR308) comprising of full depth CTDs, water sampling for analysis on-board for macro nutrient concentration and RNA sequencing of organic matter. Times Series, study data were collected as part of the Rothera Time Series (RaTS), a long-term monitoring project conducted by the British Antarctic Survey since 1997.

Data Availability

The NERC funded data collected under NE/K010034/1 is restricted to the Principal Investigator for 2 years from the point of data collection. Data is freely available to the public beyond this date.

Data Activity or Cruise Information

Data Activity

BODC Sample Metadata Report for JR20141231_CTD_18

Please note:the supplied parameters may not have been sampled from all the bottle firings described in the table above. Cross-match the Sample Reference Number above against the SAMPRFNM value in the data file to identify the relevant metadata.

Related Data Activity activities are detailed in Appendix 1

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

No Fixed Station Information held for the Series

BODC Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

Appendix 1: JR20141231_CTD_18

Related series for this Data Activity are presented in the table below. Further information can be found by following the appropriate links.

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