Major Boundary Currents and Inter-basin Flows

The circulation in the oceans around Australia. The surface currents are shown in orange and subsurface currents in green
The circulation in the oceans around Australia

As an island nation, Australia’s climate and coastal environment is strongly controlled by the complex network of currents in the surrounding ocean.  Each of the large ocean domains surrounding the continent – the Indian and Pacific subtropical gyres, the tropical oceans and Indonesian Seas, and the Southern Ocean – has a distinct but inter-connected influence on Australian climate variability and change.

Australia lies at an oceanic 'crossroads' between currents that provide the primary means of exchange between the ocean basins and therefore have a large influence on global ocean circulation and climate, such as the Indonesian Throughflow and Antarctic Circumpolar Current.  Sustained observations of the boundary currents and interbasin flows in Australia’s bluewater domain are critical for improved understanding of Australian and global climate and the factors controlling Australia’s marine environment.

The major current systems in Australia’s oceans include the East Australian Current and Leeuwin Current, carrying warm water poleward along the eastern and western boundaries of the continent, respectively; the Indonesian Throughflow providing a warm water pathway from the Pacific to the Indian Basins; the Antarctic Circumpolar Current, the largest current in the world ocean, flowing from west to east between Australia and Antarctica.

The following high-level science questions will guide the Bluewater and Climate IMOS observing strategy in this area:

Fluxes

  • How do the mass, heat, and salt transport of Australian boundary currents and inter-basin flows vary on seasonal, interannual and multidecadal timescales?
  • How do boundary current transports respond to and influence regional climate?
  • What are the relative contributions of air-sea fluxes, the mean flow, and eddies to the regional heat and freshwater budget of Australia’s oceans?

Drivers

  • What is the cause of variations in current strength?
  • How much of the change observed can be attributed to human drivers?
  • What is the relationship between boundary currents and modes of climate variability?

Dynamics

  • What is the dynamical connection between boundary currents, interbasin flows and gyres in the Australian region?
  • What are the dynamics associated with temporal changes in boundary current bifurcations, such as the bifurcation of the South Equatorial Current and the separation of the EAC from the coast?
  • What controls variations in the strength of the eddy field associated with major Australian current systems?