Southern Ocean fronts from the Greenwich meridian to Tasmania

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Journal Title: 
Journal of Geophysical Research-Oceans
Journal Date: 
Feb 15
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All available meridional sections have been analyzed to investigate the evolution of main fronts between 0 degrees and 150 degrees E. The central South Atlantic is featured by the Subtropical Frontal Zone (STFZ), bordered by the North and South Subtropical Fronts (NSTF and SSTF, respectively), and by the Polar Frontal Zone (PFZ), bordered by the Subantarctic and Polar Fronts (SAF and PF, respectively). This structure becomes more complex in the African sector as the Agulhas Retroflection and the bottom topography force a more convoluted pattern. The Retroflection and associated Agulhas Front (AF) press the SSTF from 38 degrees to 42 degrees-43 degrees S. Strong interactions of the AF, SSTF, and SAF with topography shift the fronts but do not obliterate them. The AF can be traced reliably up to 52 degrees E, sometimes up to 75 degrees E. The SAF is deflected from 45 degrees to 43 degrees S by the Mid-Ocean Ridge and converges with the SSTF north of the Prince Edward Islands to form a combined SSTF/SAF, This front intensifies east of 50 degrees-52 degrees E as a result of the confluence with the AF, and between 52 degrees and 65 degrees E a triple AF/SSTF/SAF (''the Crozet Front'') is observed. The PF continues along 49 degrees and 50 degrees S between the Crozet Plateau and the Ob-Lena (Conrad) Rise, passing north of Kerguelen,; nearly joining the triple Crozet Front. Downstream of the Kerguelen-Amsterdam Passage the canonical structure is being restored (SSTF, SAF, PF); however, the front parameters in the Australian sector are different from the African sector, largely because of strong air-sea interaction and cross-frontal exchanges in the Crozet-Kerguelen region. The SSTF, squeezed between the AF and SAF, loses characteristics to both. The SSTF/SAF interaction results in the Australian SAF being warmer and saltier downstream, while the SSTF becomes shallower and weaker. The Australian STF derives its characteristics mostly from the AF, thus bringing the modified Agulhas waters' to the Pacific Ocean. The newly defined North Subtropical Front (NSTF) was distinguished in the Indian Ocean between 31 degrees and 38 degrees S. The front marks the southern boundary of the subtropical salty, warm water pool of the central South Indian Ocean. The NSTF location is coincident with the position of the wind convergence between westerlies and easterlies, suggesting the possible wind-driven frontogenesis.


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