Southern Ocean
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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
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In September 2006, twenty-three scientists from six countries attended an Experts Workshop on Bioregionalisation of the Southern Ocean held in Hobart, Australia. The workshop was hosted by the Antarctic Climate and Ecosystems Cooperative Research Centre, and WWF-Australia, and sponsored by Antarctic expedition cruise operator, Peregrine Adventures. The workshop was designed to assist with the development of methods that might be used to partition the Southern Ocean for the purposes of large-scale ecological modelling, ecosystem-based management, and consideration of marine protected areas. The aim of the workshop was to bring together scientific experts in their independent capacity to develop a 'proof of concept' for a broad-scale bioregionalisation of the Southern Ocean, using physical environmental data and satellite-measured chlorophyll concentration as the primary inputs. Issues examined during the workshop included the choice of data and extraction of relevant parameters to best capture ecological properties, the use of data appropriate for end-user applications, and the relative utility of taking a hierarchical, non-hierarchical, or mixed approach to regionalisation. The final method involved the use of a clustering procedure to classify individual sites into groups that are similar to one another within a group, and reasonably dissimilar from one group to the next, according to a selected set of parameters (e.g. depth, ice coverage, temperature). The workshop established a proof of concept for bioregionalisation of the Southern Ocean, demonstrating that this analysis can delineate bioregions that agree with expert opinion at the broad scale. Continuation of this work will be an important contribution to the achievement of a range of scientific, management and conservation objectives, including large-scale ecological modelling, ecosystem-based management and the development of an ecologically representative system of marine protected areas. This metadata record provides links to the report from that workshop, the appendices to that report, and the ArcGIS files and Matlab code used during the workshop. The report is in PDF format. The Appendices to the report are in PDF format and contain: Appendix 1: Approaches to bioregionalisation - examples presented during the workshop Antarctic Environmental Domains Analysis CCAMLR Small-Scale Management Units for the fishery Antarctic krill in the SW Atlantic Australian National Bioregionalisation: Pelagic Regionalisation Selecting Marine Protected Areas in New Zealand's EEZ Appendix 2: Technical information on approach to bioregionalisation Appendix 3: Descriptions of datasets used in the analysis Appendix 4: Results of secondary regionalisation using ice and chlorophyll data Appendix 5: Biological datasets of potential use in further bioregionalisation work Appendix 6: Details of datasets, Matlab code and ArcGIS shapefiles included on the CD The ArcGIS archive is in zip format and contains the shapefiles and other ArcGIS resources used to produce the figures in the report. The Matlab archive is in zip format and contains the Matlab code and gridded data sets used during the workshop. See the readme.txt file in this archive for more information. Description of datasets Sea surface temperature (SST) Mean annual sea surface temperatures were obtained from the NOAA Pathfinder satellite annual climatology (Casey and Cornillon 1999). This climatology was calculated over the period 1985-1997 on a global 9km grid. Monthly values were averaged to obtain an annual climatology. Casey, K.S. and P. Cornillon (1999) A comparison of satellite and in situ based sea surface temperature climatologies, J. Climate, vol. 12, no. 6, pp. 1848-1863. Bathymetry Depth data were obtained from the GEBCO digital atlas (IOC, IHO and BODC, 2003). These data give water depth in metres and are provided on a 1-minute global grid. Centenary Edition of the GEBCO Digital Atlas, published on CD-ROM on behalf of the Intergovernmental Oceanographic Commission and the International Hydrographic Organization as part of the General Bathymetric Chart of the Oceans, British Oceanographic Data Centre, Liverpool, U.K. See http://www.gebco.net and https://www.bodc.ac.uk/projects/data_management/international/gebco/ A metadata record can be obtained from: http://data.aad.gov.au/aadc/metadata/metadata_redirect.cfm?md=AMD/AU/gebco_bathy_polygons Nutrient concentrations Silicate and nitrate concentrations were obtained from the WOCE global hydrographic climatology (Gouretski and Koltermann, 2004). This climatology provides oceanographic data on a 0.5 degree regular grid on a set of 45 standard levels covering the depth range from the sea surface to 6000m. The silicate and nitrate concentrations were calculated from seawater samples collected using bottles from stationary ships. The nutrient concentrations at the 200m depth level were used here; concentrations are expressed in micro mol/kg. https://odv.awi.de/data/ocean/woce-global-hydrographic-climatology/ Gouretski, V.V., and K.P. Koltermann, 2004: WOCE Global Hydrographic Climatology. Technical Report, 35, Berichte des Bundesamtes fur Seeschifffahrt und Hydrographie. Insolation (PAR) The mean summer climatology of the photosynthetically-active radiation (PAR) at the ocean surface was obtained from satellite estimates (Frouin et al.). These PAR estimates are obtained from visible wavelengths and so are not available over cloud- or ice-covered water, or in low-light conditions including the austral winter. Hence in the sea ice zone, this climatology represents the average PAR calculated over the period for which the water was not ice-covered. https://oceancolor.gsfc.nasa.gov/cgi/l3 Robert Frouin, Bryan Franz, and Menghua Wang. Algorithm to estimate PAR from SeaWiFS data Version 1.2 - Documentation. Chlorophyll-a Mean summer surface chlorophyll-a concentrations were calculated from the SeaWiFS summer means. We used the mean of the 1998-2004 summer values. Chlorophyll concentrations are expressed in mg/m^3. https://oceancolor.gsfc.nasa.gov/cgi/l3 Sea ice We calculated the mean fraction (0-1) of the year for which the ocean was covered by at least 15% sea ice. These calculations were based on satellite-derived estimates of sea ice concentration spanning 1979-2003. http://nsidc.org/data/nsidc-0079.html Comiso, J. (1999, updated 2005). Bootstrap sea ice concentrations for NIMBUS-7 SMMR and DMSP SSM/I. Boulder, CO, USA: National Snow and Ice Data Center. Digital media. Southern Ocean Fronts These are the front positions as published by Orsi et al. (1995). Orsi A, Whitworth T, III, Nowlin WD, Jr (1995) On the meridional extent and fronts of the Antarctic Circumpolar Current. Deep-Sea Research 42:641-673 Use of these data are governed by the following conditions: 1. The data are provided for non-commercial use only. 2. Any publication derived using the datasets should acknowledge the Australian Antarctic Data Centre as having provided the data and the original source (see the relevant metadata record listed in the description below for the proper citation).
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Samples were collected at trawl stations (approximately every second CTD station), as well as opportunistically when something interesting was spotted on the Echosounder. The samples were collected with an RMT-1 plankton net and preserved in Steedman's solution. Upon returning to Australia, the samples were passed onto Kerrie Swadling, who split them with a Folsom plankton splitter and counted between 400 and 1300 animals. Every organism was identified to the lowest possible taxon - in the case of copepods, usually to species and stage level. Other taxa are to species wherever possible. All the animals were counted and the results are expressed as abundance per 1000 cubic m. The data in the spreadsheet represent a species x site matrix. The excel spreadsheet entitled 'List of major samples and activities BROKE West.xls' is a summary of the sort of samples that were collected at each station, and the purpose for which they were collected. More detailed notes about the collection of the samples are presented in the Quality field. Further information about the Trawl stations can be found in the parent BROKE-West metadata record. This work was completed as part of ASAC projects 2655 and 2679 (ASAC_2655, ASAC_2679). The fields in these excel spreadsheets are: Station Number Species Date Latitude Longitude Trawl Type Formalin - whether the samples were fixed in formalin IGR - whether the instantaneous growth rate experiment was performed Genetics - preserved in ethanol, samples retained for genetic experiments Frozen - samples frozen at -85 degrees C for chemical analysis POP - samples analysed for Persistent Organic Pollutants Density Contrast - whether the density contrast of the krill were measured Isotopes - samples retained for isotope analysis Frozen DG - digestive gland samples were frozen Ethanol (Squid) - ethanol fixed squid were retained Frozen (Fish) - frozen fish samples were retained Formalin (Fish) - formalin fixed fish samples were retained Ethanol (Fish) - ethanol fixed fish samples were retained Demography - demographic parameters were collected Other - various purposes, occasionally noted in the comments field Comments The spreadsheet 'List of major samples and activities BROKE West.xls' is marked with solid black circles, or empty white circles - the empty white circles represent Euphausia crystallorophias samples. The solid black circles represent Euphausia superba in columns F-K, M and R. In the other columns they will either represent the animal as marked (eg squid), or may be a collection of anything.