CA 10-11 XXVI ita. Esp. South Africa SANAE 50

Extract from the 2010-2011 SANAE 50 DATA REPORT

The voyage started from Cape Town on the 8/12/2010 and returned to Cape Town on 16/02/2011.
In the period 8-19/12/2010, southward along the GoodHope hydrographic transect, with hydrographic stations occurred at regular interval using XBT and UCTD deployments which began at 33.85 S and 18.25 E, and ended at 70.5 S and 7.9 W (Fig 1).

Fig 1. Map of XBT launches in the period 08-19/12/2010 (left), and temperature section relative to the layer 0-900 m from Cape Town to Antarctica (right).

The major part of the flow associated with the ACC is concentrated at a number of circumpolar fronts, which act as boundaries separating zones of uniform water masses. From north to south the fronts and associated zones of the Southern Ocean are: Subtropical Convergence (STC), Subantarctic Zone (SAZ), Subantarctic Front (SAF), Polar Frontal Zone (PFZ), Antarctic Polar Front (APF), Antarctic Zone (AAZ) and Antarctic Divergence (AAD).
From 05/02 to 16/02/2011, northward along GoodHope hydrographic transect, hydrographic stations occurred at regular interval using a combination of XBT and UCTD deployments which began at 70.48 S and 7.7 W, and ended at 33.84 S and 17.8 W (fig 2).

Fig 2 Map of XBT launches in the period 22/02-02/03/2010(left), and temperature section relative to the layer 0-900 m from Antartica to Cape Town (right).

In the framework of the GoodHope program XBTs were funded by the NOAA's Office of Global Programs as part of their High Density XBT project at NOAA/AOML. A total of 166 Sippican Deep Blue XBTs were deployed between Cape Town and Antarctica at the GoodHope line XBTs were deployed at ~20 nautical mile intervals increasing to every ~10 nm over the main frontal regions and were alternated with UCTD casts. In total, 14 XBTs (~8%) failed mainly as a result of strong winds and sea swell blowing the running signal wire against the ship’s hull, which resulted in the XBT wire stretching and thus insulation leakages. On the return leg of the GoodHope line, 193 XBT’s were deployed of which 21 (~11%) malfunctioned. On the return leg, XBTs were deployed at higher spatial resolution northwards of ~50°S.

The aim of the GoodHope programme is to establish an intensive monitoring platform that will provide detailed information on the physical structure and volume flux of waters south of South Africa, where the inter-basin exchanges occur. A key component of this programme is the implementation of the high-density XBT line AX25 that runs from Cape Town to Antarctica.
The SANAE cruise track crossed four distinct oceanic domains: the seasonal marginal ice-edge zone, the permanently open ocean zone, the shelf zone of the South Sandwich and South Georgia Islands and the frontal zones of the Antarctic Polar Front, the Subantarctic Front and the Subtropical Front.