The mean properties and variations of the Southern Hemisphere subpolar gyres estimated by Simple Ocean Data Assimilation (SODA) products

Based on the Simple Ocean Data Assimilation (SODA) products, we study the mean properties and variations of the Southern Hemisphere subpolar gyres (SHSGs) in this paper. The results show that the gyre strengths in the SODA estimates are (55.9 +/- 9.8)x10(6) m(3)/s for the Weddell Gyre (WG), (37.0 +/- 6.4)x10(6) m(3)/s for the Ross Gyre (RG), and (27.5 +/- 8.2)x10(6) m(3)/s for the Australian-Antarctic Gyre (AG), respectively. There exists distinct connectivity between the adjacent gyres and then forms an oceanic super gyre structure in the southern subpolar oceans. And the interior exchanges are about (8.0 +/- 3.2)x10(6) m(3)/s at around 70A degrees E and (4.3 +/- 3.1)x10(6) m(3)/s at around 140A degrees E. The most pronounced variation for all three SHSGs occurs on the seasonal time scale, with generally stronger (weaker) SHSGs during austral winter (summer). And the seasonal changes of the gyre structures show that the eastern boundary of the WG and AG extends considerably further east during winter and the interior exchange in the super gyre structure increases accordingly. The WG and RG also show significant semi-annual changes. The correlation analyses confirm that the variations of the gyre strengths are strongly correlated with the changes in the local wind forcing on the semi-annual and seasonal time scales.