ISSUE 182 : Jul/Aug - 2010 - Australian Defence Force Journal

The ‘Sea Change’ report is highly relevant to this article, since it addresses Defence’srelationship to the ocean environment, in its broadest sense, and places it in a national andinternational context. It reminds us that Australia has the third largest maritime jurisdictionon earth, even before one includes the waters off our Antarctic territories, and that the oceansoffer great potential for ‘soft power’ and creative diplomacy. This presents Australia withunique opportunities to use the sea to promote our national interests.The ASW challengeIn order to detect and respond to submarines, we need to understand, assess and predict thephysical oceanography of the region. Oceanic temperature and salinity structures have a hugeeffect on sonar propagation, while currents, eddies, fronts and the shape and characteristicsof the sea bed can all be exploited by submarines, both acoustically and for the purposes ofmanoeuvre. Surface conditions, such as swell and wind waves, must also be understood andpredicted, since they affect radar and visual detection opportunities.Oceanographic conditions vary greatly between one part of the world’s oceans and seas andanother. The oceanographic conditions of the Timor Sea, for example, are very different tothose of the Coral Sea, the Tasman Sea or the South China Sea. Marine life, uneven bottomtopography, tidal streams and currents are all factors that add greatly to the ambient noise ofthe undersea environment and can affect markedly the performance of sonar systems. As wedevelop our capabilities for situational awareness in the undersea domain, we will need toshare oceanographic information within the maritime force and with shore centres. We willalso need to create novel products to assist the warfighter and integrate oceanographic datawith tactical decision aids and weapon and sensor systems.The Defence White Paper defines the ADF’s ‘primary operational environment’ as extendingfrom the eastern Indian Ocean to the island states of Polynesia, and from the equator tothe Southern Ocean. It includes maritime Southeast Asia and waters and littoral areas of theSouth Pacific and Indian Ocean. The sea-air gap is declared to be at the ‘strategic centre’ ofour primary operational environment. This region is characterised by exceptionally complexphysical oceanography.Further afield, the poorly-understood Pacific-Indonesian ‘through-flow’ 6 affects the Timor andArafura Seas, and the Northwest Shelf. Also, ‘upwelling’ events, in which cold water is broughtto the near-surface layers by particular wind patterns, take place throughout the region. 7Around Australia, they occur along the Queensland and NSW coasts and in the waters off thecoast of South Australia, where maritime patrol aircraft of 92 Wing RAAF frequently exercise.Upwellings have a huge impact on the ocean’s acoustic properties, acting like a ‘brick wall’ inthe ocean, behind which submarines can hide.6