SACO-10W-11S

Figure 1.1

The cruise SACO-10W-11S is planned for March 2025. SACO-10W-11S will be a cruise dedicated to maintain the PIES of the SAGA array, deploy another one at 14.5ºS and to carry out a hydrographic cruise at 10W and 11S. Initially, the SAGA array, which consisted of 3 moorings and 4 PIES, was deployed in April 2021. The instruments in the moorings have autonomy for 2 years, so they were recovered in April 2023 in a programmed cruise with the R.V. Hespérides. In contrast, the PIES has an autonomy of up to five years and they will be providing data for another two years. Hence, we plan to maintain them in April 2025 with the SACO-10W-11S cruise. In addition, this 2025 cruise will carry out a full hydrographic section at 10ºW and 11ºS. It will sample the water masses in the middle of the subtropical South Atlantic region and western boundary where the deep flow separates in the western and eastern components as well as the connections between the South Atlantic subtropical and tropical gyres. The SACO-10W-11S cruise will complement the transoceanic cruise carried out along 34.5ºS in February 2022 (SAGA-34.5S), allowing the application of a full-transoceanic inverse model. During this cruise, the IEO team will obtain the inorganic nutrients and the QUIMA team from IOCAG (ULPGC) will obtain the oxygen and CO2 system. Nutrients will be measured in every cast and bottle, and oxygen and CO2 systems will be measured in 80-85 bottles every day with the VINDTA EC system.
Figure 1.2

SACO-SO-2025

Figure 2

The two Southern Ocean cruises aim at determining the water exchange between the Weddell Sea and the deep waters north of the South Scotland Ridge, and its effect on the lower branch of the Southern Ocean vertical cell and on the Antarctic Slope Current north of this Ridge. The first of these cruises, SACO-SO-2025, is planned to last 14 days in January-February 2025 (considering the departure and arrival in Ushuaia or Punta Arenas; this time is halved if we consider the departure and arrival at the Spanish Antarctic Base).

The cruise will focus on the Hesperides Trench within the South Scotia Ridge, with one single meridional hydrographic section of about 19 high-resolution stations (separated by only 10 km) crossing the Ridge along the Trench. Nutrients, oxygen and the CO2 system will also be measured as in SACO-10W-11S. Additionally, an instrumented mooring (with instruments also provided by CICESE) will be installed in the Hespérides Trench to monitor the processes that cause deep-water export through this region.

SACO-SO-2026

Figure 3

The second cruise, SACO-SO-2026, will recover the mooring installed in one of the western passages of the South Scotia Ridge and repeat the hydrographic section related to the mooring to estimate the interannual change of bottom waters. This second campaign, to be carried out in January 2026, will last 25 days (considering the departure and arrival in Ushuaia or Punta Arenas; this time is reduced to 20 days if we consider the departure and arrival at the Spanish Antarctic Base).

The cruise will consist of seven hydrographic sections with a total of 119 high-resolution stations (separated by only 10 km) sampling the Bransfield Strait and the northwestern margin of the Weddell Sea. In some 20 stations there will be additional microstructure measurements. The cruise will also carry out a high-resolution sampling of selected regions with the help of the SeaSoar undulating vehicle, and will sample the Hesperides Trench and the northern slope of the South Scotia Ridge with an instrumented glider (provided by the CICESE researchers in the working group). As part of the cruise the instrumented mooring will be recovered.