Major Boundary Currents and Inter-basin Flows

Flow streams in the western Pacific (source Steinberg 2007)
Flow streams in the western Pacific (source Steinberg 2007)

The South Equatorial Current (SEC) from the western Pacific Ocean forces the inflow of both boundary currents in Queensland (EAC, Gulf of Papua Current). The SEC flows westwards into the eastern Coral Sea at depths to at least 1000 m but with evidence of vertical shear near the coast. This deepening of the bifurcation with latitude means that there is a deep undercurrent, known as the Great Barrier Reef (GBR) Undercurrent, flowing northwest through the Queensland Trough underneath the southward flowing surface expression of the EAC offshore of the central and southern GBR.

South of the GBR, the subsurface flows from the SEC become continuous with the surface expression of the EAC and both tightly track the Continental Slope south of Fraser Island. The EAC is strongest and most coherent south of the GBR where it tracks the continental margin closely. The EAC plays a critical role in removing heat from the tropics and releasing it to the mid-latitude atmosphere. This heat transfer is a dominant environmental influence on regional climate and fisheries production along the eastern seaboard.

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

Dynamics:

  • Will the EAC strengthen with climate change as predicted?
  • Will the GPC weaken with climate change as predicted?
  • Will the bifurcation point and/or dynamics alter in a warmer ocean?