This project used computer-based modelling and existing field data to analyse the production and cycling of dimethylsulphide (DMS) and predicted its role in climate regulation in the Antarctic Southern Ocean. From the Final Report: Aims (i) To calibrate an existing dimethylsulphide (DMS) production model in a section of the Antarctic Southern Ocean. (ii) To use the calibrated model to investigate the effect of GCM-predicted climate change on the production and sea-to-air flux of DMS under current and enhanced greenhouse climatic conditions. (iii) To provide regional assessments of the sign and strength of the DMS-climate feedback in the Southern Ocean. Characteristics of Study Region: Our study region extends from 60-65 degrees S, 123-145 degrees E in the Antarctic Southern Ocean, and was the site of a major biological study in the austral summer of 1996 (Wright and van den Enden, 2000). Field observations show that a short-lived spring-summer bloom event is typical of these waters (El-Sayed, 1988, Skerratt et al. 1995); however there can be high interannual variability in the timing and magnitude of the bloom (Marchant and Murphy, 1994). The phytoplankton community structure has been described by Wright and van den Enden (2000), who report maximum chlorophyll (Chl) concentrations during January-March in the range (1.0-3.4) microgL-1. During this survey, macronutrients did not limit phytoplankton growth. Thermal stratification of the mixed layer was strongly correlated with high algal densities, with strong subsurface Chl maxima (at the pycnocline) observed. The mixed layer depth determined both phytoplankton community composition and maximum algal biomass. Coccolithophorids (noted DMS producers) were favoured by deep mixed layers, with diatoms dominating the more strongly stratified waters. Pycnocline depth varied from 20-50 m in open water. Algal abundance appeared to be controlled by salp and krill grazing. Field data support the existence of seasonal DMS production in the Antarctic region. However, a large range in DMS concentrations has been reported in the open ocean , reflecting both seasonal and spatial variability (Gibson et al., 1990, Berresheim, 1987; Fogelqvist, 1991). Blooms of the coccolithophores, and prymnesiophytes such as Phaeocystis, form a significant fraction (~23%) of the algal biomass (Waters et al 2000). Concentrations of DMS in sea ice are reported to be very high (Turner et al. 1995) and may be responsible for elevated water concentrations during release from melt water (Inomata et al. 1997). Field measurements of dissolved DMS made in the study region have been summarised by Curran et al. (1998). DMS concentrations were variable in the open ocean during spring and summer (range: 0-22 nM), with the higher values recorded in the seasonal ice zone and close to the Antarctic continent. Zonal average monthly mean DMS in the study region have been estimated by Kettle et al. (1999). (See downloadable full report for reference list). A copy of the referenced publication is also available for download by AAD staff. It contains the modelling information.

Continuous underway measurements of sea surface (7 metres depth)dissolved gasses (co2, o2, argon, nitrogen)by quadrupole mass spectrometry (Electron Impact Mass Spectrometry - EIMS). ASCII encoded. 1 file per 24 hours. Naming convention: YYMMDD. Excel readable format. Column data (0/0 refers to ion mass, 7 ION masses detected in total): Cycle Date Time RelTime[s] '0/0' '0/1' '0/2' '0/3' '0/4' '0/5' '0/6' '0/7' '1/0' '2/0' '2/1' '2/2' '2/3' '2/4' '2/5' '2/6' '2/7' Measurements were made on the CEAMARC voyage of the Aurora Australis - voyage 3 of the 2008-2008 summer season.

Production of the arsenic species total inorganic arsenic [As(V+III)],arsenite [As(III)], monomethyl arsenic (MMA) and dimethyl arsenic (DMA) was studied in the Subantarctic Zone (SAZ) of the Southern Ocean, south of Australia, during the austral autumn (March 1998). Surface samples were collected approximately every degree of latitude along the meridional transect 14130' E from 42 to 55 S. In addition, representative vertical profiles were collected at: 4206' S, 14153' E (Subtropical Convergence Zone - STCZ), 4643' S, 14159' E (Subantarctic Zone - SAZ), 5104' S, 14336' E (Subantarctic Front - SAF) and 5344' S, 14142' E (northern branch of the Polar Frontal Zone - PFZ). As(V) was the dominant arsenic species in both vertical profiles and surface waters along the transect. It was also the only species observed at depths greater than 600 m. Production of the reduced arsenic species (As(III), MMA, DMA) was low in these waters compared with other oceanic sites with similar concentrations of chlorophyll a. As(III) concentrations could not be reliably quantified at any sites (less than 0.04 nM). Greatest conversion of arsenic to 'biological' species was found at the surface in the Subtropical Convergence Zone (2.5%) and decreased heading southward to 1% in the Polar Front (PF). While the decline in methyl arsenic production was broadly associated with water temperature and measures of biological production, slightly different trends in methyl arsenic production were found in the SAZ and PF. North of the Subantarctic Front (SAF) methyl arsenic production was well correlated with water temperature, while south of the front no such relation existed. In addition, the ratio of DMA/MMA increased south of the SAF, associated with a change in the microalgal community composition. Low water temperature, phosphate-replete conditions and low biological productivity in the SAZ all contribute to the concentrations of biologically produced arsenic species in this region being amongst the lowest reported for oceanic waters. The data are stored in an excel spreadsheet, and a readme text file.

These data describe the field deployments of the trace-metal passive sampling tools, diffusive gradients in thin-films (DGT). Deployments occurred over the summer 2017/2018 season in the coastal region adjacent to Casey and Wilkes stations. Deployments of DGT to the nearshore marine environment was achieved with small watercraft and shallow (less than 5m deep) moorings, which were left in situ for 21-37 days, depending on the site.

Continuous underway measurements of sea surface (7 metres depth)and atmospheric carbon dioxide. Data format .txt extension comma delimited files. 1 file per 24 hours. Naming similar to AA03607_001-0000 (voyage_julian day_HH:MM). Excel readable format. 58 columns of data. Measurements were made on the CEAMARC voyage of the Aurora Australis - voyage 3 of the 2008-2008 summer season.

Hydrochemistry of surface water. Parameters measured=salinity, oxygen, co2, oxygen isotope species, nutrients. All data have been stored in a single excel file. Measurements were made on the CEAMARC voyage of the Aurora Australis - voyage 3 of the 2008-2008 summer season. See other CEAMARC metadata records for more information.

These data describe the locations, dates, time, etc where biogeochemistry data were collected on the CEAMARC-CASO cruise in the 2007/2008 Antarctic season. See the CEAMARC-CASO events metadata record for further information. Sample codes are not descriptive. CEMARC/CASO column have underway data (no link to group site) as well as the CEAMARC and CASO sampling locations. Events are recorded by number and the associated type of sample taken. CTD - 0.4 um filtered water sample. Box corer - diatom scrape. Beam Trawl AAD - sponge sample. PHY - phytoplankton sample taken from inline surface seawater system. Van Veen grab - sediment scrape. WAT - surface water sample passed through 0.4 um filter. Description column explains the samples in more detail - eg information on what size fraction the phytoplankton were filtered at. Litres column describes the volume of water that was filtered. Depth is in metres. Time is local time. Temperature is degrees C. Storage location was for shipboard use only. The "other" column details any extra information that may be useful to the sample for example #2153 refers to a sample id code that the French CEAMARC group was using to code for their samples. Our aim for this voyage was to collect surface phytoplankton and water samples across a transect of the Southern Ocean, and to collect benthic sponge and coral samples in Antarctica, to (i) measure the Ge/Si and Si isotope composition to construct a nutrient profile across the Southern Ocean, and to test and calibrate these parameters as proxies for silica utilisation; and (ii) measure the B isotope composition to test the potential of biogenic silica to be used as a seawater pH proxy. We collected phytoplankton, sponges, diatom sediment scrapes and water samples at strategic locations to ensure that the entire water column was surveyed. The data that were collected were used in collaboration with palaeoenvironmental data from sediment cores and experimental culture experiments on diatoms and sponges to gain a better understanding of historical distributions of Silicon and pH in the Southern Ocean.

Zooplankton grazing experiments using the dilution method have been conducted for 2 months at Davis station and on a weekly basis in order to investigate the relationship between zooplankton grazing rates and DMS production in surface water during the blooming season. Regular water sampling in conjunction with these experiments has been conducted to quantify pigments and phytoplankton populations in the same waters. This work was completed as part of ASAC project 2100 (ASAC_2100). The dataset also includes methods used to obtain the data. The fields in this dataset are: chlorophyll DMS DMSP Pigment Dilution

The dataset lists key biogeochemical parameters measured in sea ice during the SIPEX2 voyage, including dissolved and particulate iron and other trace metals, macronutrients (silicic acid, nitrates+nitrite, phosphoric acid and ammonium), iron binding organic ligands, dissolved and particulate organic carbon, Cholophylla, thermodynamics (temperature, salinity, brine volume and Rayleigh number). All sampling bottles and equipment were decontaminated using trace metal clean techniques. Care was taken at each site to select level ice with homogeneous snow thickness. At all the stations, the same sampling procedure has been used : Firstly, snow was collected using acid cleaned low density polyethylene (LDPE) shovels and transferred into acid-cleaned 3.8 l LDPE containers (Nalgene). Snow collected was analysed for temperature, salinity, nutrients, unfiltered and filtered metals. Snow thickness was recorded with a ruler. Ice cores were collected using a non-contaminating, electropolished, stainless steel sea ice corer (140 mm internal diameter, Lichtert Industry, Belgium) driven by an electric power drill. Ice cores were collected about 10 cm away from each other to minimise between-core heterogeneity. A first core was dedicated to the temperature, salinity and Chlorophyll a (Chla). To record temperature, a temperature probe (Testo, plus or minus 0.1 degrees C accuracy) was inserted in holes freshly drilled along the core every 5 to 10 cm, depending on its length. Bulk salinity was measured for melted ice sections and for brines using a YSI incorporated Model 30 conductivity meter. Chla is processed on board using a 10 AU fluorometer (turner Designs, sunnyvale California). The total length of this core is cut in sections of 7 cm. The second core is dedicated to the POC/PON (Particulate Organic Carbon/ Particulate Organic Nitrogen), DOC (Dissolved Organic Carbon) and nutrients. Six sections of 7 cm were sub-sampled from this core. The six sections were chosen so that two top, two intermediate and two basal sections. Two cores are taken for the trace metal analysis. Those cores were directly triple bagged in plastic bags (the inner one is milli-Q washed) and frozen at -20degrees C until analysis at the laboratory. Brine samples were collected by drainage from “sack holes”. Brines and under ice seawater (~1 m deep) were collected in 1 l Nalgene LDPE bottles using an insulated peristaltic pump and acid cleaned C-flex tubing (Cole Palmer). All samples were then transported to the ship as quickly as possible to prevent further freezing. Samples were used to analyse unfiltered and filtered metals, Chla, POC/PON, nutrients and DOC. Filtration for filtered metals was completed on board using a peristaltic pump and a 0.2 microns cartridge filter. All the unfiltered and filtered metals collected were acidified (2 ppt HCl seastar) and stored at room temperature until analysis at the laboratory. Nutrients, DOC and filters for POC/PON were stored frozen at -20 degrees C until analysis at Analytical Service Tasmania, Hbart. Chla filtrations and analysis were completed on board. The file "SIPEX2 sea ice data" lists key biogeochemical parameters in sea ice cores, snow, brine and underice seawater (1m depth) collected during the SIPEX2 voyage (64.26-65.15S/116.44-120.58E) carried out between the 26th of september and 29th of october 2012. The acid-cleaning protocols for sample bottles and equipment followed the guidelines of GEOTRACES (www.geotraces.org). Contamination-free ice coring equipment developed by Lannuzel et al. (2006) was used to collect ice cores. Ice cores were triple bagged and stored at -18 degrees C until further processing in the home laboratory. Ice cores were then sectioned under a class-100 laminar flow hood (AirClean 600 PCR workstation, AirClean System) using a medical grade stainless steel bonesaw (Richards Medical), thouroughly rinsed with ultra-high purity water (18.2 MO), and ice sections were then allowed to melt at ambient temperature in acid-cleaned 3 L Polyethylene (PE) containers. Melted sea-ice sections were then homogenized by a gentle shake and filtered through 0.2 microns pore size polycarbonate filters (Sterlitech, 47 mm diameter) using Teflon(R) perfluoroalkoxy (PFA) filtration devices (Savillex, USA) connected to a vacuum pump set on less than 2 bar to obtain the particulate (greater than 0.2 microns) and dissolved (less than 0.2 microns) metal fractions. The collected filtrates (less than 0.2 microns) were acidified to pH 1.8 using Seastar Baseline(R) HCl (Choice Analytical) and stored at ambient temperature until analysis in the home laboratory. The filters retaining the particulate material were stored frozen in acid-clean petri dishes until further processing. Standard physico-chemical and biological parameters such as sea-ice and snow thicknesses, in situ ice temperature, sea-ice and brine salinities, ice texture, chlorophyll a (Chla), macro-nutrients (nitrate+nitrite (NOx), phosphate (PO43-), silicic acid (Si(OH)4-) and ammonium (NH4+)), dissolved organic carbon (DOC), and particulate organic carbon and nitrogen (POC and PON) were also determined in each sample at Analytical Service Tasmania (Hobart, Australia) within 6 months of sample collection. Dissolved inorganic nutrients were determined using standard colorimetric methodology (Grasshoff et al., 1983) as adapted for flow injection analysis using an auto-analyzer. Theoretical brine volume fractions (Vb/V) were calculated using in situ ice temperatures and bulk ice salinities and relationships from Cox and Weeks (1983). The full ice core length was examined under crossed-polarised light to identify the texture (i.e., columnar vs granular) according to the method of Langway (1958). Preparation of the thin sections took place in a container kept at -25 degrees C. The thin sections were obtained by cutting vertical sections of about 6 mm thick using a band saw. Ice sections were then thinned down using a microtome blade to reach a final thickness of 3 - 4 mm and observed under cross-polarized lights The acidified filtrates were diluted 5 times, using 2 % v:v ultrapure HNO3 (Seastar Baseline, Choice Analytical) and dissolved metals concentrations were determined directly using sector field inductively coupled plasma magnetic sector mass spectrometry (SF-ICP-MS; Element 2) following the method described in Lannuzel et al. (2014). Filters retaining particulate material (greater than 0.2 microns) were digested in a mixture of strong, ultrapure acids (750 micro litres 12N HCl, 250 microlitres 40% HF, 250 microlitres 14N HNO3) in 15 mL Teflon(R) perfluoroalkoxy (PFA) (Savillex, USA) on a Teflon coated graphite digestion hot plate housed in a bench-top fume hood (all DigiPREP from SCP Science, France) coupled with HEPA(R) filters to ensure clean air input at 95 degrees C for 12 h, then dry evaporated for 4 h and re-suspended in 2 % v:v HNO3 (Seastar Baseline, Choice Analytical). The procedure was applied to filter blanks and certified reference materials BCR-414 and MESS-3 to verify the recovery of the acid digestion treatment. The concentrations of particulate metals were then determined by SF-ICP-MS (Bowie et al., 2010). Results for procedural blanks, limits of detection and certified reference materials were found fit for purpose. The file "SIPEX2 TMR data" lists macro-nutrients concentrations, as well as dissolved iron concentrations collected using a Trace Metal Rosette (TMR) deployed over 1000m depth in the sea ice zone. Dissolved iron (DFe) and iron in the 2+ redox state (FeII) in nanomoles per Litre (nmol/L) were measured onboard using FIA-CL technique explained in Schallenberg et al (2015). Standard deviation associated with the analysis of the samples is indicated by "SD". Dissolved Fe(III): Dissolved Fe in this study is operationally defined as the Fe fraction that passes through a 0.2 microns filter. A modified flow injection analysis (FIA) method was used to measure dFe that relies on the detection of Fe(III) with the chemiluminescent reagent luminol (de Jong et al., 1998; Obata et al., 1993). Samples and standards were treated with hydrogen peroxide (H2O2; final concentration = 10 micro mols) at least 1 hour prior to measurement to oxidize any Fe(II) that might be present (Lohan et al., 2005). The system buffers the samples in-line to pH = 4 before passing them for 3 minutes through a pre-concentration column packed with 8-hydroxyquinoline chelating resin (8-HQ). A solution of 0.3 M HCl (Seastar) then elutes Fe(III) from the resin and mixes with 0.8 M ammonium hydroxide (NH4OH), 0.1 M H2O2 and 0.3 mM luminol containing 0.3 mM triethylenetetramine (TETA) and 0.02 M sodium carbonate (Na2CO3), yielding an optimum luminol chemiluminescence reaction pH of 9.5. The resulting solution is passed through a ~5 m mixing coil maintained at 35 degrees C before being pumped to the flow cell mounted in front of a photo-detector. System blanks were 0.014 plus or minus 0.004 nM, yielding a detection limit (3 x blank standard deviation) of 0.013 nM. Results for SAFe reference materials for Fe were in good agreement with consensus values (see Table 1). Dissolved Fe(II): Fe(II) was determined by luminol chemiluminescence detection following the approach of Hansard and Landing (2009) but without sample acidification. Sampling began within minutes after the first Niskin bottle (always from the surface) arrived in the clean container. Samples were analyzed within 2 minutes of filtration and were pumped simultaneously with the luminol reagent into a spiral flow cell made of flexible Tygon(TM) tubing (ID = 0.7 mm) that was mounted in front of a photomultiplier tube (Hamamatsu H9319-01) in a custom-made light-tight box. Flow rates for luminol and sample were ~4.5 mL/min. The photomultiplier tube was operated at 900 V with a 200 ms integration time. Photon counts were recorded using FloZF software (GlobalFIA) and were averaged over 10 second intervals with 5 replications for each sample and standard. The relative standard deviation of these repeat measurements was between 1 and 3%. The luminol recipe for 1 L reagent is as follows: 0.13 g luminol, 0.34 g Na2CO3, 40 mL concentrated NH4OH and 10-12 mL concentrated HCl (Seastar). This results in 0.75 mM luminol with 3.2 mM Na2CO3. The pH of the reagent is adjusted to ~10.0 with small amounts of NH4OH and HCl. It was found that luminol sensitivity increases with age, so batches were prepared well in advance and used up to 3 months later. Fe(II) calibration curves were obtained with Fe(II) standard additions in the range 0-100 pM. A 10 mM standard of ammonium iron(II) sulfate hexahydrate was prepared fresh in 0.1 M Seastar HCl and considered stable in the fridge for up to a month. From this stock solution, intermediate standards (50 micro mols and 50 nM) were prepared in 0.05 M Seastar HCl no more than 10 minutes prior to measurement. Standards were added to seawater that had been collected at earlier stations in the cruise and been left in the dark for greater than 24 hours. Previous investigators (e.g., Rose and Waite, 2001) have commented on the light-sensitivity of the luminol reagent, and it is therefore frequently stored in the dark.

Metadata record for data from ASAC Project 2297: Iron content of Southern Ocean phytoplankton: implications for carbon transfer to the deep sea. Data on size-fractionated distribution of suspended trace elements (including iron) in marine particles taken from the surface Southern Ocean south of Australia. Data for 4 size-fractions at 4 stations along ~142 degrees E are included. Explanation of codes used in the dataset: The isotope of the element of interest is listed down column A. LR refers to low resolution and MR medium resolution (that is the resolution of the ICPMS analytical instrument). So Mn55(LR) is the manganese isotope 55 ran in low resolution. SFP1_2um_B2_1: SFP=size-fractionated particles 1=station 1 2um=2micron filter size B2=blank 2 1=replicate 1 RSD%=relative standard deviation in % Blank=field blank Blk/sample%=blank-to-sample ratio in % CRMs_261102=certified reference materials (ran on 26 Nov 2002) Scaled up=previous column times multiplication factor (a serial dilution was used) Blk=blank subtracted certified=the value certified by the manufacturer of the reference material SLRS_1in25_1= the CRM 'SLRS', ran with a 1 in 25 dilution factor, replicate 1 DigBlk1_1=digestion blank 1, replicate 1 See the link below for public details on this project.