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GEOMACS (Geological and Oceanographic Model of Australia's Continental Shelf) Q25

Note: This metadata describes the dataset in accordance with the ANZLIC (Australia New Zealand Land Information Council) Core Metadata Guidelines Version 2.


Dataset citation

ANZLIC unique identifier: ANZCW0703015175

Title: GEOMACS (Geological and Oceanographic Model of Australia's Continental Shelf) Q25


Custodian

Custodian: Geoscience Australia

Jurisdiction: Australia


Description

Abstract:

Geoscience Australia's GEOMACS model was utilised to produce hindcast hourly time series of

continental shelf (~20 - 300 m depth) bed shear stress (unit of measure: Pascal, Pa) on a 0.1

degree grid covering the period March 1997 to February 2008 (inclusive). The hindcast data

represents the combined contribution to the bed shear stress by waves, tides, wind and densitydriven

circulation.

Included in the parameters that represent the magnitude of the bulk of the data are the quartiles

of the distribution; Q25, Q50 and Q75 (i.e. the values for which 25, 50 and 75 percent of the

observations fall below). Q25, or the 0.25 Quartile of the Geomacs output, represents the values

for which 25% of the observations fall below (Hughes & Harris 2008).

ANZLIC search words:

  • GEOSCIENCES Mapping
  • MARINE

Spatial domain:

locality map

Geographic extent name: AUSTRALIA EXCLUDING EXTERNAL TERRITORIES - AUS - Australia - Australia

Geographic extent polygon: 110 -7, 156 -7, 156 -44, 110 -44, 110 -7,

Note: The format for each Geographic extent name is: Name - Identifier - Category - Jurisdiction (as appropriate) See GEN Register

Geographic bounding box:
North bounding latitude: -7 °
South bounding latitude: -44 °
East bounding longitude: 156 °
West bounding longitude: 110 °

Data currency

Beginning date: 2008-07-24

Ending date: 2008-07-24


Dataset status

Progress: Complete

Maintenance and update frequency: Not Known


Access

Stored data format:
DIGITAL - ArcGIS-grid ArcInfo grid WGS84
Available format type:
DIGITAL - ArcGIS-grid ArcInfo grid WGS84

Access constraints:

This material is released under the Creative Commons Attribution 3.0 Australia Licence.

Free Data Download

Data quality

Lineage:

The Geological and Oceanographic Model of Australia?s Territory (GEOMAT- Harris et al., 2000)

developed at Geoscience Australia provides maps indicative of seabed exposure on the

Australian continental shelf in depths between approximately 20 m and 300 m. GEOMAT v.1

proposed a classification of the Australian underwater territory based on sediment mobility

induced by distinct processes such as tidal currents and gravity waves (Porter-Smith et al.,

2004). GEOMAT v.2 (GEOMACS) proposed an improved classification of the continental shelf

area based on a seabed exposure index (Hemer, 2006). The seabed exposure index was

derived from the statistical distribution of the sediment transport rate, which reflected the

strength and frequency of the combined wave-current bed shear stress. The bed shear stress

was derived from a bottom boundary layer model (SEDTRANS - Li and Amos, 2001), which

integrated the combined action of tidal currents (Egbert et al., 1994), oceanic currents (OCCAM;

Webb et al., 1998), and gravity waves (AUSWAM - Greenslade, 2001) over a given mean

sediment fraction (MARS; Geoscience Australia, 2006).

Positional accuracy:

The dataset is estimated on a 0.1deg grid resolution.

Attribute accuracy:

Output is from a mathematical model ? there are no direct field observations. The GEOMACS

model does not include the effects of wave breaking and refraction/diffraction or non-linear

shallow-water effects on the tide, therefore the model is not considered useful in <10 m water

depth, and in many regions in <30 m water depth; depending on the dominant wave period, tidal

range and bathymetric complexity (Hughes & Harris 2008). Conversely, seabed disturbance

produced by the wave, tide and current input variables appears not to extend beyond 300 m

depth. The temporal domain includes 11 years and therefore contains limited information on

events with long return intervals at specific locations, e.g. tropical cyclones (Hughes & Harris

2008).

Logical Consistency:

All model outputs data have been visually checked for artefacts and spurious data. Tests

conducted to ensure data are reliable and valid.

Completeness:

Completed


Contact information

Contact organisation: Commonwealth of Australia (Geoscience Australia) (GA)
Contact position: Manager Client Services
Mail address: Cnr Jerrabomberra Ave and Hindmarsh Dr
Mail address: GPO Box 378
Locality: Canberra
State: ACT
Country: Australia
Postcode: 2601
Telephone: 02 6249 9966
Facsimile: 02 6249 9960
Electronic mail address: sales@ga.gov.au

Metadata information

Metadata date: 2013-03-08


Additional metadata

Metadata reference XHTML: http://www.ga.gov.au/meta/ANZCW0703015175.html

Metadata reference XML: http://www.ga.gov.au/meta/ANZCW0703015175.xml

Egbert, G.D., Bennett, A.F., and Foreman, M.G.G., 1994. TOPEX/POSEIDON tides estimated

using a global inverse mode. Journal of Geophysical Research 99, 24821-24852.

Greenslade, D.J.M., 2001. The Assimilation of ERS-2 Significant Wave Height Data in the

Australian region. Journal of Marine Systems 28, 141-160.

Harris, P. T., Smith, R., Anderson, O., Coleman, R., and Greenslade, D., 2000. GEOMAT ?

modelling of continental shelf sediment mobility in support of Australia?s regional marine

planning process. Australian Geological Survey Organisation Record 2000/41.

Geoscience Australia, Canberra. 53pp.

Hemer, M.A., 2006. The magnitude and frequency of combined flow bed shear stress as a

measure of exposure on the Australian continental shelf. Continental Shelf Research

26, 1258-1280.

Hughes, M., Harris, P. T., 2008. Progress Report on Disturbance Task C1, Surrogates Program,

Marine Biodiversity Hub. Geoscience Australia, Canberra.

Hughes, M., Harris, P. T., and Brooke, B. P. (In press). Seabed exposure and ecological

disturbance on Australia?s continental shelf: Potential surrogates for marine biodiversity.

Geoscience Australia Record 2010/XX. Geoscience Australia, Canberra.

Li, M.Z., and Amos, C.L., 2001. SEDTRANS96: the upgraded and better calibrated sediment

transport model for continental shelves. Computers and Geosciences 27, 619-645.

Porter_Smith, R., Harris, P.T., Anderson, O., Coleman, R., Greenslade, D.J.M., and Jenkins,

C.J., 2004. Classification of the Australian continental shelf based on predicted

sediment threshold exceedance from tidal currents and swell waves. Marine Geology

211, 1-20.

Webb, D.J., Cuevas, B.A., and Coward, A.C., 1998. The first main run of the OCCAM global

ocean model. Internal Report of James Rennell Division, Southampton Oceanography

Centre, UK. 50pp. See also:http://www.noc.soton.ac.uk/JRD/OCCAM.

Authors:Hughes, M.G. Harris, P.T.
SPATIAL INFORMATION FOR THE NATION