Processed underway Thermosalinograph (TSG) observations from the Southern Ocean Seasonal Experiment 2022 on the SA Agulhas II Voyage 053, July 2022

Here we present the 6-second resolution processed Thermosalinograph (TSG) data collected between 12 July and 30 July 2022 on the SA Agulhas II Voyage 053. A SeaBird SBE45 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). This cruise was included as a final component of the SCALE programme (Southern oCean seAsonaL Experiment, https://scale.org.za), a bottom-up endeavour of the SA scientific community to address the limited multidisciplinary knowledge on the seasonal cycle of the Southern Ocean. The seasonal cycle is an important mode of variability that couples the physical mechanisms of climate forcing to ecosystem response in phytoplankton diversity, primary production, and carbon export. Model simulations of the Southern Hemisphere tend to misestimate the magnitude and miss the timing of the Southern Ocean seasonal cycle both in terms of the seasonality of surface ocean warming and cooling, sea ice advancement/retreat, carbon dioxide exchanges and simulated primary production. Our capability to predict the ongoing shifts and future responses is therefore limited. This drives the need for more physical and biogeochemical data sets that address the problem of knowledge and model biases; firstly, to identify them, and secondly to characterise the associated mechanisms that will allow improved projections.