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| Tasman Outflow | |
|---|---|
| Name | Tasman Outflow |
| Location | Tasman Sea, Southern Ocean, South Pacific |
| Source | East Australian Current, Tasman Sea |
| Terminus | Southern Ocean, Antarctic Circumpolar Current |
| Status | Active |
Tasman Outflow.
The Tasman Outflow is a southward and eastward oceanic pathway that exports water from the Tasman Sea and the western South Pacific Ocean into the Southern Ocean and the Antarctic Circumpolar Current. It constitutes a distinct limb of circulation connected to the East Australian Current, the Subtropical Gyre, and the Indonesian Throughflow and interacts with major features such as the Drake Passage, the Tasman Front, and the Circumpolar Front. Studies of the outflow involve institutions including the CSIRO, the University of Tasmania, the Scripps Institution of Oceanography, and the National Oceanic and Atmospheric Administration.
The Tasman Outflow is recognized as a coherent export route linking western Pacific Warm Pool-influenced waters from the Coral Sea and eastern Indian Ocean sectors to the Southern Ocean conveyor that feeds into the Antarctic Circumpolar Current. Observational programs by the Integrated Ocean Drilling Program, the World Ocean Circulation Experiment, and the Southern Ocean State Estimate initiative identified its signatures across hydrographic sections and float trajectories. Research by groups at the Woods Hole Oceanographic Institution, the Australian Bureau of Meteorology, and the National Centre for Atmospheric Research has emphasized its role in connecting planetary-scale features like the Subtropical Front and the South Pacific Gyre.
The pathway carries modified East Australian Current waters along the continental slope and across the Tasman Sea through mesoscale structures such as eddies and jets that interact with bathymetry including the Lord Howe Rise and the Norfolk Ridge. The outflow threads between the Subtropical Front, the Subantarctic Front, and the Polar Front before merging with the Antarctic Circumpolar Current near the Drake Passage corridor. It is characterized by transports measured in Sverdrups by deployments from the Argo Program, mooring arrays funded by the Global Ocean Observing System, and tracer releases coordinated with the International Geophysical Year legacy studies.
Formation mechanisms involve wind-driven processes from the South Pacific Convergence Zone and the Roaring Forties westerlies, baroclinic instability of the East Australian Current retroflection, and exchange across the Tasman Front mediated by mesoscale eddies and submesoscale filaments. Interactions with topographic obstacles like the Macquarie Ridge and the Bounty Trough induce steering and mixing, while buoyancy forcing from the Tasman Sea heat budget and exchanges with the Indonesian Throughflow modulate density gradients that set baroclinic shear. Numerical experiments by groups at the Met Office Hadley Centre, the Geophysical Fluid Dynamics Laboratory, and the University of Washington have explored eddy-permitting and eddy-resolving regimes relevant to formation.
The outflow provides a conduit for subtropical waters to feed the Antarctic Circumpolar Current, influencing the upper limb of the meridional overturning components associated with the Southern Ocean Meridional Overturning Circulation and teleconnections to the Pacific Meridional Overturning Circulation. By connecting the Tasman Sea with the Southern Ocean, it affects pathways linked to the global thermohaline circulation, the Atlantic Meridional Overturning Circulation via interbasin exchanges, and the distribution of tracers relevant to carbon cycle studies undertaken by the International Ocean Carbon Coordination Project. Its exchanges have implications for surface fluxes studied by the Global Energy and Water Exchanges Project and coupling with atmospheric modes such as the El Niño–Southern Oscillation, the Indian Ocean Dipole, and the Southern Annular Mode.
Waters exported include modified Subtropical Mode Water, Subantarctic Mode Water, and upper-ocean layers influenced by the East Australian Current heat and salt content, with temperature and salinity ranges reflecting contributions from the Coral Sea and subtropical gyre inflow. Variability arises from seasonal shifts tied to the Interdecadal Pacific Oscillation, interannual modulation by El Niño–Southern Oscillation, and longer-term trends associated with anthropogenic warming documented by the Intergovernmental Panel on Climate Change. Biogeochemical properties such as oxygen, nutrient, and carbon content are monitored by programs like the Global Carbon Project and the Biogeochemical-Argo initiative to assess impacts on biological productivity and sequestration.
By exporting warm, saline waters poleward, the outflow influences sea surface temperature patterns that affect climate phenomena observed by the Commonwealth Scientific and Industrial Research Organisation and regional climate services in Australia, New Zealand, and the Pacific Islands Forum. Changes in transport can alter heat uptake in the Southern Ocean, with downstream effects on sea-ice distributions observed by the National Aeronautics and Space Administration and European Space Agency satellite missions. Ecosystem impacts include shifts in habitat for species documented by the Commission for the Conservation of Antarctic Marine Living Resources and fisheries managed under the Australian Fisheries Management Authority and regional bodies like the Western and Central Pacific Fisheries Commission.
Observational evidence combines satellite altimetry from missions by the European Space Agency and NASA, in situ profiles from the Argo Program, tracer experiments associated with the Global Ocean Ship-based Hydrographic Investigations Program, and moored arrays supported by the Australian National Facility for Ocean Gliders. Modeling studies use configurations from the CMIP6 ensembles, high-resolution configurations developed at the University of Oxford and Princeton University, and data-assimilative products such as the Ocean Reanalysis System 5. Key analyses have been published by researchers affiliated with the University of New South Wales, the University of Cape Town, and the Lamont–Doherty Earth Observatory.
Category:Ocean currents Category:South Pacific Ocean Category:Southern Ocean