Keyword

AMD/AU

1705 record(s)
 
Type of resources
Topics
Keywords
Contact for the resource
Provided by
From 1 - 10 / 1705
  • Metadata record for data from ASAC Project 545 See the link below for public details on this project. From the abstract of the referenced paper: Blood was collected for haematological, red cell enzyme and red cell metabolic intermediate studies from 20 Southern elephant seals Mirounga leonina. Mean haematological values were: haemoglobin (Hb) 22.4 plus or minus 1.4 g/dl, packed cell volume (PCV) 54.2 plus or minus 3.8%, mean cell volume (MCV) 213 plus or minus 5 fl and red cell count (RCC) 2.5 x 10 to power 12 / l. Red cell morphology was unremarkable. Most of the red cell enzymes showed low activity in comparison with human red cells. Haemoglobin electrophoresis showed a typical pinniped pattern, ie two major components. Total leucocyte counts, platelet counts, and coagulation studies were within expected mammalian limits. Eosinophil counts varied from 0.5 x 10 to power 9 / l (5%-49%), and there was a very wide variation in erythrocyte sedimentation rates, from 3 to 60mm/h.

  • During the ADBEX III voyage, many samples were taken of the sea ice and snow. These samples were analysed to determine water density, with the results recorded in a physical note book that is archived at the Australian Antarctic Division. Logbook(s): - Glaciology ADBEX III Water Density Results - Glaciology ADBEX III Oxygen Isotope Sample Record

  • Metadata record for data from ASAC Project 1119 See the link below for public details on this project. A marked bend in the Hawaiian-Emperor seamount chain supposedly resulted from a recent major reorganization of the plate-mantle system there 50 million years ago. Although alternative mantle-driven and plate-shifting hypotheses have been proposed, no contemporaneous circum-Pacific plate events have been identified. We report reconstructions for Australia and Antarctica that reveal a major plate reorganization between 50 and 53 million years ago. Revised Pacific Ocean sea-floor reconstructions suggest that subduction of the Pacific-Izanagi spreading ridge and subsequent Marianas/Tonga-Kermadec subduction initiation may have been the ultimate causes of these events. Thus, these plate reconstructions solve long-standing continental fit problems and improve constraints on the motion between East and West Antarctica and global plate circuit closure.

  • A geomorphology map of the Australasian seafloor was created as a Geographic Information System layer for the study described in Torres, Leigh G., et al. "From exploitation to conservation: habitat models using whaling data predict distribution patterns and threat exposure of an endangered whale." Diversity and Distributions 19.9 (2013): 1138-1152. The geomorphology map was generated using parameters derived from the General Bathymetric Chart of the World (GEBCO 2008, http://www.gebco.net/), with 30 arc-second grid resolution. Geomorphology features were delineated manually with a consistent spatial resolution. Each feature was assigned a primary attribute of depth zone and a secondary attribute of morphological feature. The following feature classes are defined: shelf, slope, rise, plain, valley, trench, trough, basin, hills(s), mountains(s), ridges(s), plateau, seamount. Further information (methods, definitions and an illustration of the geomorphology map) is provided in Appendix S2 of the paper which is available for download (see related URLs).

  • The dataset submitted here is 'Sea-ice freeboard derived from airborne laser scanner'. Between 2007 and 2012, the Australian Antarctic program operated a scanning LiDAR system and other scientific instruments for sea-ice geophysical surveys in East Antarctica. For example see Lieser et al. [2013] for the 2012 survey. The dataset here provides the sea-ice freeboard (i.e. elevation above sea level) along various helicopter flight lines of the 2012 survey in the sea-ice zone between 113 degE and 123 degE. The data collection was based on: - Riegl LMS Q240i-60 scanning LiDAR, measuring sea ice elevation above the WGS84 reference ellipsoid; - Hasselblad H3D II 50 camera, taking aerial photographs at about 13 cm resolution every 3-5 seconds (older digital camera used in 2007); - inertial navigation and global positioning system, OxTS RT-4003. The following geophysical corrections were applied to the sea-ice elevations to derive the sea-ice freeboard: - geoid correction (from the EGM2008 Earth gravity model); - mean ocean dynamic topography correction (from the DTU Space model - DTU10MDT); - ocean tide correction (from the Earth and Space Research CATS2008 Antarctic tide model); - atmospheric pressure (inverse barometer effect) correction from ECMWF data (4-year average) and ship-board underway observations. The geophysical corrections have been validated along selected flight lines by extracting ocean surface elevations from leads between ice floes as identified in the aerial photography. Contained in this dataset are the following files: - a netCDF file for 8 selected flights of the 2012 survey containing sea-ice freeboard values; - a postscript file for 4 of the 8 selected flights showing the residuals from the applied geophysical corrections. These 4 flights were selected on the basis of having a good spread of observable leads along the entire flight line that enabled the extraction of ocean surface elevations.

  • The RAN Australian Hydrographic Service conducted hydrographic survey HI242 at Macquarie Island in November and December 1996. The main survey areas were Buckles Bay and Hasselborough Bay. Survey lines were also followed from Elliott Reef down the west coast to Langdon Bay and down the east coast to Buckles Bay. The survey dataset, which includes metadata, was provided to the Australian Antarctic Data Centre by the Australian Hydrographic Office and is available for download from a Related URL in this metadata record. The survey was lead by LT M.A.R.Matthews. The data are not suitable for navigation.

  • Metadata record for data from ASAC Project 2960 See the link below for public details on this project Public The ocean's thermohaline circulation (THC) plays a fundamental role in global climate, transporting heat poleward and regulating the uptake of anthropogenic CO2. Multiple steady-states in the THC have been identified in the North Atlantic, including an "off" state where no deep water is formed, yet little is known regarding the possibility for multiple equilibria of the Southern Ocean THC. This study aims to (1) examine hysteresis behaviour and possible multiple equilibria of the Southern Ocean THC, and (2) quantify the role of the Southern Ocean THC by examining the difference between "on" and "off" states in various water-masses. Project objectives: The overarching goal of the proposed study is to explore the possibility of multiple steady-states of the Southern Ocean (SO) thermohaline circulation (THC) and to explore their role in the global climate system. Multiple steady-states in the ocean's THC have been identified in the Northern Hemisphere [e.g., Marotzke, 2000; Rahmstorf, 2002]. While substantial climate variability and change can be inferred from palaeoclimate data for the Southern Hemisphere, our understanding of the underlying physics of SO THC variability and the associated climate dynamics remains limited. It is also unclear how the Southern Ocean THC will change in the future. This study aims to: 1. Examine the hysteresis behaviour of the Southern Ocean thermohaline circulation in relation to surface freshwater forcing, both for AABW and AAIW, 2. Explore the possibility for multiple steady-states in the Southern Ocean THC, 3. Estimate how the present-day Southern Ocean THC may be changing in relation to this hysteresis diagram, and how this relates to global climate, and 4. Quantify the role of the present-day Southern Ocean THC by examining the difference between "on" and "off" states. Taken from the 2008-2009 Progress Report: Progress against objectives: Progress on this Antarctic Sciences project during 2008/2009 can be summarised as below. Each of the four main aims have been touched upon during the past 12 months, although the most significant progress has been against items 1, 3, and 4 as listed in Section 1.1 above. The existence of teleconnections of Southern Ocean freshwater anomalies to the North Atlantic THC was investigated, primarily in the context of past climates (Trevena, Sijp and England, 2008a). We found that a Southern Ocean freshwater pulse of comparable magnitude to meltwater pulse 1A, shuts down, instead of strengthens, NADW in a glacial climate simulation. Unlike a modern-day simulation, the glacial experiment is associated with a more fragile North Atlantic thermohaline circulation, whereby freshwater anomalies that propagate into the North Atlantic are able to dominate the bipolar density see-saw. The possibility for large-scale collapse and/or multiple steady-states in the Southern Ocean THC was also investigated using a coupled climate model of intermediate complexity. Also investigated was the impact of a slowdown of Antarctic Bottom Water (AABW) on regional Southern Hemisphere climate. This involved the gradual addition of meltwater anomalies to strategic locations of the Southern Ocean, then removal of these anomalies to explore whether the regional thermohaline circulation (THC) exhibits saddle-node instabilities (bifurcation points) as have been commonly found for the North Atlantic. We found that no stable AABW "off" state could persist, regardless of the freshwater anomaly imposed. We did, however, identify a significant impact on regional climate during the transient slow down of AABW (Trevena, Sijp and England, 2008b). In particular, during peak FW forcing, Antarctic surface sea and air temperatures decrease by a maximum of 2.5 degs C and 2.2 degs-C respectively. This is of a similar magnitude to the corresponding response in the North Atlantic. Taken from the 2009-2010 Progress Report: Progress against objectives: Progress on this Antarctic Sciences project during 2009/2010 can be summarised as below. Each of the four main aims have been touched upon during the past 12 months, although the most significant progress has been against items 2 and 4 as listed in Section 1.1 above. A large set of experiments were configured and analysed to examine Southern Ocean THC states in the global climate system. Specifically we conducted experiments using the Canadian University of Victoria Earth System Climate Model (the 'UVic' model) wherein the model is perturbed in some way to explore the possibility for multiple steady-states in the Southern Ocean THC. Where multiple steady states were obtained, the difference between "on" and "off" states was examined to quantify the role of the Southern Ocean THC in global climate. Three papers were published in the 2009/2010 period that were produced using support from this Antarctic Research project:- Sijp, W. P., M. H. England, and J.R. Toggweiler, 2009: Effect of ocean gateway changes under greenhouse warmth, J. Climate, 22, 6639-6652. In this study Southern Ocean gateway changes and the THC were examined under a suite of atmospheric CO2 levels, spanning pre-industrial (280 ppm) up to values relevant to the Eocene (1500 ppm). A markedly stronger gateway response is found under elevated CO2 levels, suggesting past work has underestimated the effects of gateway changes at the Oligocene-Eocene boundary. Sen Gupta, A., A. Santoso, A.S. Taschetto, C.C. Ummenhofer, J. Trevena and M.H. England, 2009: Projected changes to the Southern Hemisphere ocean and sea-ice in the IPCC AR4 climate models, J. Climate, 22, 3047-3078. In this study simulations of the Southern Ocean THC, water-masses, and mixed layer depth were examined and compared across a series of IPCC-class global climate models, under both present-day and climate change scenarios. Sijp, W. P. and M. H. England, 2009: The control of polar haloclines by along-isopycnal diffusion in climate models, J. Climate, 22, 486-498. In this study the ocean THC was shown to be sensitive to along-isopycnal diffusion rates in global climate models. This potentially impacts on past studies wherein multiple equilibria were obtained at unrealistic values of this mixing parameter.

  • Our understanding of how environmental change in the Southern Ocean will affect marine diversity,habitats and distribution remain limited. The habitats and distributions of Southern Ocean cephalopods are generally poorly understood, and yet such knowledge is necessary for research and conservation management purposes, as well as for assessing the potential impacts of environmental change. We used net-catch data to develop habitat suitability models for 15 of the most common cephalopods in the Southern Ocean. Full details of the methodology are provided in the paper (Xavier et al. (2015)). Briefly, occurrence data were taken from the SCAR Biogeographic Atlas of the Southern Ocean. This compilation was based upon Xavier et al. (1999), with additional data drawn from the Ocean Biogeographic Information System, biodiversity.aq, the Australian Antarctic Data Centre, and the National Institute of Water and Atmospheric Research. The habitat suitability modelling was conducted using the Maxent software package (v3.3.3k, Phillips et al., 2006). Maxent allows for nonlinear model terms by formulating a series of features from the predictor variables. Due to relatively limited sample sizes, we constrained the complexity of most models by considering only linear, quadratic, and product features. A multiplier of 3.0 was used on automatic regularization parameters to discourage overfitting; otherwise, default Maxent settings were used. Predictor variables were chosen from a collection of Southern Ocean layers. These variables were selected as indicators of ecosystem structure and processes including water mass properties, sea ice dynamics, and productivity. A 10-fold cross-validation procedure was used to assess model performance (using the area under the receiver-operating curve) and variable permutation importance, with values averaged over the 10 fitted models. The final predicted distribution for each species was based on a single model fitted using all data: these are the predictions included in this data set. The individual habitat suitability models were overlaid to generate a 'hotspot' index of species richness. The predicted habitat suitability for each species was converted to a binary presence/absence layer by applying a threshold, such that habitat suitability values above the threshold were converted to presences. The threshold used for each species was the average of the thresholds (for each of the 10 training models) chosen to maximize the test area under the receiver-operating curve. The binary layers were then summed to give the number of species estimated to be present in each pixel in the study region.

  • In January 2005 a multi-parametric international experiment was conducted that encompassed both Deception Island and its surrounding waters. This experiment used as main platforms the Spanish Oceanographic vessel 'Hesperides', the Spanish Scientific Antarctic base 'Gabriel de Castilla' at Deception Island and four temporary camps deployed on the volcanic island. This experiment allowed us to record active seismic signals on a large network of seismic stations that were deployed both on land and on the seafloor. In addition other geophysical data were acquired, such as: bathymetric high precision multi-beam data, and gravimetric and magnetic profiles. During the whole period of the experiment a multi-beam sounding EM120 was used to perform bathymetric surveys. The characteristic of this sensor permitted to reach up to 11.000 m b.s.l. In table 2 we provide some of its main characteristics. During the experiment different bathymetric profiles were performed with this equipment outside of Port Foster. Some of these images already have provide an accurate vision of the region, and were used to estimate the real size of the water column locate below each shoot. Additional information of these data could be found in the Lamont-Doherty Earth Observatory at IEDA Marine Geoscience Data System (http://www.marine-geo.org/). It is possible to access the summary of downloads that were made of these data and documents at http://www.marine-geo.org/about/downloadreport/person/Ibanez_Jesus/2016A.

  • This consolidated dataset consists of Australian Hydrographic Service (AHS) surveys HI621C, 5135 (Terrestrial), HI364, HI514, and HI607 converted to International Terrestrial Reference Frame 2000 (ITRF2000) horizontal datum with Z conversion values for multiple height datums. The data was provided to the AAD by Paul Digney of Jacobs consulting in February 2021. Included survey datasets: • HI621C_MAWSON_merged.shp • HI621C_MAWSON_merged.shp • Terrestrial_Data_5135 • HI364_HSDB_T0001_SD_100035029_op_soundings • QC_HI 514 HDCS_FDD_appraised (Mawson Approches) • HI607.Shp All data are in horizontal datum ITRF2000 and have been combined into a single ESRI geodatabase feature class titled AHS_Surveys_Mawson_ITRF2000. Attribute data shows quality information, conversion factors (shift in metres) for multiple datums and the MSL orthometric height: Column Name, Alias, Meaning Easting, Easting, Easting ITRF2000 Northing, Northing, Northing ITRF2000 CD_To_GRS8, CD_To_GRS80, LAT (Chart Datum) to the Ellipsoid LAT_to_GRS80, LAT_to_GRS80, LAT (Chart Datum) to GSR80 LAT_to_MSL_Mawson, LAT_to_MSL_Mawson, LAT to Mawson MSL Z_To_GRS80, Z_To_GRS80, Height to the Ellipsoid Z_To_MSL_Mawson, Z_To_MSL_Mawson, Local MSL orthometric height Vertical_U, Vertical_Uncertainty, How good is the Vertical Position Horizontal, Horizontal Uncertainty, How good is the Horizontal Position Uncertaint, Uncertainty Comments, Depth_Comm, Depth_Comments, Vertical uncertainty ranges from 0.05 to 0.64 m and horizontal uncertainty ranges from 0.05 to 1.0 m See the attached document ‘Metadata_Record_Mawson Final REV2.xlsx’ for further details.