Total Organic Carbon A 2 g homogenised wet sediment sub-sample from each core was weighed into a pre-combusted crucible and dried at 105 degrees C. The dried sample was reweighed before being analysed for total carbon by mass loss on ignition at 550 degrees C, the sample was placed in the muffle furnace for 4 hours. Samples 56698, 57062, 56837, 57058, and 580792 were analysed in triplicate to assess the reproducibility of the analytical procedure. (Total number of analyses was 117). - TOC - For the 107 samples: - Mean and SD: 3 plus or minus 4 % DMB, range: 0.16-15 %, n=107 - Considering the mean values for the 27 site locations: - Range: 0.33-14 % DMB, mean and SD: 3.3 plus or minus 3.7 % DMB, n=27 - Analytical uncertainty - Analytical precision: 5 samples analysed in triplicate: - RSD = 6 plus or minus 5% range 1-11%, n=5 - Site heterogeneity: reproducibility (RSD) of mean data from site replicate samples was 26% (mean, SD 15%, range 10-57%, n=27) - From the limited data on reproducibility summarised above, it can be concluded that site heterogeneity contributes most to the uncertainty of the TOC data for the site locations. - DMF - For the 107 samples: - Mean and SD: 0.57 plus or minus 0.23 %, range: 0.09-0.85, n=107 - Considering the mean values for the 27 site locations: - Range:0.17-0.83, mean and SD: 0.57 plus or minus 0.22, n=27 - Analytical uncertainty - Analytical precision: 5 samples analysed in triplicate: - RSD = 2 plus or minus 2% range 0.8-5%, n=5 - Site heterogeneity: reproducibility (RSD) of mean data from site replicate samples (mostly quadruplicates) was 10% (mean, SD 10%, range 1-37%, n=27) - From the limited data on reproducibility summarised above, it can be concluded that site heterogeneity contributes most to the uncertainty of the DMF data for the site locations. Collection of sediment cores Sediment for grain size and various chemical analysis were sampled using a core of PVC tubing (15cm long x 5cm diameter) pushed 10cm into the sediment. These cores were kept upright at all times to ensure the stratigraphy remained intact and frozen in the core tube at -20 degrees C. Grain size analysis The outer 5 mm edge of the core was removed with a scalpel blade and placed in a clean, dried preweighed beaker. The sample was weighed and placed in an oven at 45 degrees C to dry. Once dry the sample was reweighed and then sieved through a 2 mm sieve, any residual sediment in the beaker was weighed and the weight recorded. The less than 2 mm fraction and the greater than 2 mm fraction were separately collected and weighed. A 5 g sample of the less than 2 mm fraction was taken for grain size analysis which was carried out using the Mastersizer 2000 Particle Size Analyser by Associate Professor Damian Gore at the Department of Physical Geography, Macquarie University, Sydney.

Metadata record for data from ASAC Project 133 See the link below for public details on this project. Surface carbon dioxide (CO2) observations are integral to understanding the role of the Southern Ocean in the global carbon cycle, and to developing reliable predictions of biogeochemical responses to altered climatic conditions. Carbon dioxide (CO2) observations made in surface waters of the Australian sector of the Southern Ocean between the years 1991 and 2002 were used to estimate the seasonal variability in the fugacity of CO2 (fCO2) and net air-sea carbon fluxes. The results showed a net annual uptake of CO2 by the surface ocean over the entire region. The greatest seasonal uptake and lowest fCO2 values were observed in Spring/Summer in the sub-Antarctic zone (SAZ: 44 degrees S-50 degrees S) and in the Seasonal Sea-ice Zone (SIZ: south of 62 degrees S). The seasonal maximum in uptake for these regions is consistent with increased phytoplankton biomass and shoaling mixed layers over the Spring/Summer period. The High Nutrient Low Chlorophyll waters between 50 degrees S and 62 degrees S, also had maximum uptake in summer, but less compared to the SAZ and SIZ regions. Winter surface waters were close to or slightly above equilibrium, with respect to atmospheric CO2. The reduced uptake in winter appeared due to deeper mixing, lower biomass, and air-sea CO2 exchange. The highest fCO2 values in Winter were observed under or near the seasonal sea-ice where entrainment of deeper CO2-rich waters and ice cover would maintain high surface fCO2 values. The smallest seasonal amplitude in the surface fCO2 and net air-sea fluxes was found from 51 degrees S to 54 degrees S, a region on the southern edge of the SAZ and between the North sub-Antarctic Front and North Polar Front. The uptake estimates derived from the data were in good agreement with the CO2 flux climatology of Takahashi (2002), except in the SAZ and SIZ where we observed greater and less uptake, respectively. Data for this project are available for download - the dataset consists of a data files, and some excel files, which provide further information about each data file (cruise, dates, etc). Furthermore, the column headings used in the data files are as follows: Cruise - name of the cruise which collected the data Date - UTC Time - in UTC Latitude - decimal Longitude - decimal Sst - Sea Surface Temperature in degrees C Teq - Temperature of surface water at which the CO2 measurement is made. Sal - Salinity Patm - atmospheric pressure in hectopascals Shipspd - ship speed in knots Windspd - wind speed in knots Winddir - wind direction in degrees xCO2 - Mole fraction of CO2 in air (dry) equilibrated with surface water and at equilibrator water temperature xCO2air - Mole fraction of CO2 in atmosphere, dry pCO2 - partial pressure of carbon dioxide in surface water