Fronts and upper ocean thermal variability south of New Zealand

Abstract

The structure and variability of Southern Ocean fronts south of New Zealand are described based on fifteen summer expendable bathythermograph (XBT) sections obtained between 1994 and 2001. The temperature variability north of 60°S is dominated by meanders and meridional shifts of the Sub-Antarctic Front (SAF), which often bifurcates to form northern and southern branches. The northern branch follows the southern edge of the Campbell Plateau, while the southern branch is found over the abyssal plain of the south-west Pacific Basin. The northern and southern branches of the SAF can be separated by as much as 900 km. Intense eddies or meanders of the SAF displace isotherms by as much as 5 degrees of latitude from their positions when such features are absent. The Polar Front (PF) position is more stable in time, although cold-core features associated with eddies or meanders of the front are occasionally observed between the southern SAF and the PF. The position of the southern ACC front is extremely stable, consistently overlying the 3000 m isobath on the northern flank of the Pacific-Antarctic/south-east Indian Ridge.