Repeat Hydrography Along 34.5 ˚S

GO-SHIP’s quasi-decadal re-occupation of hydrographic transects spanning the global oceans was implemented and is sustained to quantify changes in the storage and transport of heat, fresh water, carbon, nutrients, and transient tracers (Talley et al., 2016; Sloyan et al., 2019; also Figure 3). These full-depth, coast-to-coast transects measure many of the physical and biogeochemical Essential Ocean Variables of the Global Ocean Observing System and provide the highest accuracy ocean data, attainable only with research ships and specialized, calibrated analytical methods (Figures 4–5).

GO-SHIP is an international component of the Global Ocean Observing System (GOOS). GO-SHIP provides climate-ready, full-depth observations of most of the physical (temperature, salinity, velocity) and biogeochemical (carbon, nutrients, oxygen, trace elements) parameters needed to track changes in climate. The high accuracy of GO-SHIP data make them the underlying backbone of GOOS, as benchmarks for calibration and validation of autonomous observations. GO-SHIP station tracks are repeated every 5 to 10 years, which allows comparison of heat, freshwater, carbon and nutrient distributions over decades.

The GO-SHIP A10.5 location, nominally along 34.5 ˚S,  is the latitude where the north-south transport between the Atlantic and the rest of the world ocean is now being monitored.

GO-SHIP A10.5 was previously occupied in 2017 using vessel Maria S Merian, MSM60. There are no other full occupations of this section, although there have been nearby repeated sections along ‘A10’, at 30°S. The A10.5 track was introduced to avoid major topographic features in the west, and provide a clean east-west crossing of the Argentine Basin in the southwest Atlantic. A10.5 crosses the Brazil Current at the coast of South America, and the Agulhas/Benguela at the coast of Africa.  

Because this latitude has been selected for monitoring exchange between the Atlantic and the World Ocean, there are current meter arrays that sample these boundary currents: the SAMBA arrays at South America and the SAMOC arrays at the African coast.  These are maintained by a multi-national group of South African, US, Argentinian, Brazilian, French and German scientists.  Parts of A10.5 are therefore frequently occupied by research ships for servicing the array that often perform CTD stations. Hydrographic measurements made on the array servicing cruises often meet the criteria to be associated GO-SHIP cruises.

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Chief scientist: Alonso Hernanez-Guerra