|
Numerical simulations of the global ocean analyzed with a Lagrangian methodology are used to describe and quantify the paths, transports, and characteristics of the upper branch of the global thermohaline circulation. Our main results can be summarised as follows:
- We diagnosed three distinct origins external to the Indo-Atlantic sector for the water masses reaching the North Atlantic Ocean. To the two classical sources, the Drake Passage (DRAKE) and Indonesian Throughflow (ITFL), our analyses add a third one, the westward flow south of Tasmania (TAS).
- The ORCA DRAKE and ITFL transports are almost equivalent (6.8 and 5.8 Sv respectively). The TAS contribution is less but not negligible (3.2 Sv).
- The three origins hypothesis prove to be robust as their existence is found in different simulations of the global ocean performed with distinct G.C.M.s.
- 18 Sv is the ORCA amplitude of the return flow: an internal Indo-Atlantic upwelling of NADW contribution of 2.2 Sv has to be added to the 15.8 Sv coming from the three origins mentioned before. The 18 Sv value compares well with transport estimates of the A17 WOCE section.
- In term of water characteristics, the ORCA simulation suggests that is TAS and not DRAKE (as commonly believed) the major provider of intermediate waters at the equator in the Atlantic.
|
Conclusions
