Rosemary Morrow et al., Observed subsurface signature of Southern Ocean sea level rise

Progress in Oceanography, 77 (4), 351-366, June 2008. doi:10.1016/j.pocean.2007.03.002


Observed subsurface signature of Southern Ocean sea level rise

Rosemary Morrow^, , Guillaume Valladeau and Jean-Baptiste Sallee

LEGOS/OMP, 18 Av. Edouard Belin, 31401 Toulouse Cedex 9, France

(Received 11 September 2006;

accepted 28 March 2007.

Available online 10 April 2008.)

Abstract

Satellite altimetry data show a strong increase in sea level in various parts of the Southern Ocean over the 1990s. In this paper, we examine the causes of the observed sea level rise in the region south of Australia, using 13 years of repeat hydrographic data from the WOCE SR3 sections, and the SURVOSTRAL XBT and surface salinity data. The hydrographic data show a poleward shift in the position of the Subtropical and the Subantarctic Fronts over the period. In the Antarctic Zone, the Antarctic Surface Water has become warmer and fresher, and the Winter Water tongue has become warmer, fresher, thinner and shallower. Increased freshening south of the Polar Front is linked to increased precipitation over the 1990s. Temperature changes over the upper 500 m account for only part of the altimetric sea level rise. The CTD sections show that the deeper layers are also warmer and slightly saltier and the observed sea level can be explained by steric expansion over the upper 2000 m. ENSO variability impacts on the northern part of the section, and a simple Sverdrup transport model shows how large-scale changes in the wind forcing, related to the Southern Annular Mode, may contribute to the deeper warming to the south.

Link to abstract: doi:10.1016/j.pocean.2007.03.002