The main science objectives during M124 are:
1) Comparison between direct and indirect estimates on upper ocean meridional heat/freshwater transport across the South Atlantic following the AX18(*) section
2) Gain knowledge on the diversity, ecology and extent of the trans-oceanic gene flow in planktonic foraminifera between Indian, Pacific and South Atlantic Ocean
3) Long term changes in Antarctic Bottom Water temperature/salinity in the Vema Channel
4) Accuracy of remotely sensed estimates of aerosol as well as atmospheric and oceanic optical properties, and precipitation estimates, flux of momentum and turbulent heat fluxes over the South Atlantic
5) Tests of a new optode based sensor for measuring surface water pCO2
6) Occurrence of persistent pollutants in surface waters
After leaving Cape Town we follow a north/northwestern course. With support from home institutions we will adjust the track slightly in order to survey Agulhas Rings. The atmospheric measurements will start immediately after the cruise start. The measurements are performed continuously and do not require any stations, nor ship gear, nor technical support from the deck personnel.
Underway measurements with uCTD, RapidCast, and XBTs will be started shortly after leaving Cape Town (depending on the clearance for EEZ waters) and in high frequency (approx. every hour). TSG sampling will also start as soon as possible and so will current observations with the shipboard ADCP’s. Water depth soundings will be done continuously. A deep CTD rosette (METEOR device) will be done (preferentially in a “young” Agulhas Ring) shortly after leaving Cape Town. The towed fish is used to pump water on board into a through-flow container where samples will be taken.
About once a day a multinet/CTD rosette cast will be done. The multinet samples will be analysed for foraminiferas with the microscope. The rosette samples will be analysed for salinity and oxygen (CTD sensor calibration) as well as nutrients, and carbon system parameters. In the Vema Channel region full depth CTDs rosette samples will be acquired.The CTD data (salinity, oxygen) will be validated on board against analysis of oxygen and salinity in water samples. This procedure will ensure high quality data and also a tracking the quality of the data during the cruise.
Past 180 days eddy detection on weekly mean sea-level-anomaly (SLA) data provided by AVISO