Water samples were taken during the Southern Atlantic expedition PS103 with RV Polarstern from 17 Dec 2016 to 28 Jan 2017. Water samples were collected from CTD Niskin bottles at six different depths from the upper 100 to 180 m. The same water samples as in Bracher (2019) are filtered for CDOM absorption analysis through 0.2 µm filters and analysed onboard with a 2.5-m path length liquid waveguide capillary cell system (LWCC, WPI) following Levering et al. (2017). Details on method adaptation to our instrumentation set-up are provided in Alvarez et al. (2022). Salinity data were extracted from https://doi.pangaea.de/10.1594/PANGAEA.881076.

Further specifications on the measurements:a) Instrument set-up:light source: UV-VIS lamp (Mikropack DH-2000 Deuterium-Tungsten Halogen Light Source, Artisan Technology Group, USA)cuvette: Liquid Waveguide Capillary Cell system (LWCC, World Precision Instruments Inc, USA) with 197.8 cm pathlengthdetector: photodiode array spectrometer (Sensline AVASPEC-2048-RS, Avantes, Netherlands)pump: Ismatec Reglo Analogb) configurations:wavelength range of scan and resolution: 200.0-760.0 nm, 0.3 nm.slit band width: 1 nm.Dark current was recorded before each sample measurement and samples were measured against reference of MQ three times.c) further specifications about data analysis:interpolated wavelength range and resolution: 350-730 nm, 1nm. Salinity correction applied based on CTD and thermosalinograph data.