Processed near-surface underway temperature and salinity (TSG) observations from the SEAmester and ASCA Scientific Cruise on the SA Agulhas II Voyage 052, June 2022

Here we present the 6-second resolution processed Thermosalinograph (TSG) data collected on the SEAmester and Agulhas System Climate Array (ASCA) Scientific Cruise on the SA Agulhas II Voyage 052 between 27 June and 07 July 2022. The cruise operated from Cape Town to the ASCA transect (~ 34°S) off Hamburg in the Eastern Cape, South West Indian Ocean. A SeaBird SBE45 Thermosalinograph (TSG) is used to opportunistically collect underway near-surface temperature and conductivity measurements during research and monitoring cruises. Water is continuously pumped to the TSG from an intake located in the hull of the vessel, and the observations are continuously interfaced with navigational information. A temperature sensor close to the intake provides temperature measurements of the incoming water (T1). The temperature of the water inside the conductivity cell (T2) is used to accurately compute salinity (S) from the conductivity measurements (C). The objective of the SEAmester cruise was to undertake the ASCA transect across the Agulhas Current and sample the 20 CTD stations done previously. In addition, SEAmester shallow (200m) CTD training stations would take place each day at 10am and 4pm for the students. Due to the change of plans requested of the SEAmester team to undertake a medical evacuation at Marion Island, the science team opted to instead study a trapped lee-edge cyclonic eddy formed due to an early retroflection of the Agulhas Current. The timing of the cruise provided a unique opportunity to study a phenomena rarely occurring, and the placement allowed the vessel to be positioned closer to Marion Island when weather allowed for the medical evacuation from Marion Island.