Laurent,
I thought that I would add the following links and sample attached images (the last image is of the Dotson Getz Trough) regarding high resolution Southern Ocean bathymetry charts that can be downloaded for free:
Arndt, JE et al. (2013): The International Bathymetric Chart of the Southern Ocean (IBCSO) - digital bathymetric model. doi:10.1594/PANGAEA.805734,
In Supplement to: Arndt, Jan Erik; Schenke, Hans Werner; Jakobsson, Martin; Nitsche, Frank-Oliver; Buys, Gwen; Goleby, Bruce; Rebesco, Michele; Bohoyo, Fernando; Hong, Jong Kuk; Black, Jenny; Greku, Rudolf Kh; Udintsev, Gleb B; Barrios, Felipe; Reynoso-Peralta, Walter; Taisei, Morishita; Wigley, Rochelle (2013): The International Bathymetric Chart of the Southern Ocean Version 1.0 - A new bathymetric compilation covering circum-Antarctic waters. Geophysical Research Letters, online first, doi:10.1002/grl.50413
http://www.awi.de/en/news/press_releases/detail/item/a_sharper_look_into_the_southern_ocean/?cHash=71f1d6e5c0538ad59e3fba02dbeca9cb