Spectrophotometric measurements of absorption coefficients by total particles, phytoplankton and non-algal particles during POLARSTERN cruise PS93.2

Measurements were performed using a dual-beam UV/VIS spectrophotometer as described in Liu et al. (2018) and Liu et al. (2019). 1. About sampling: a) underway samples were collected from unfiltered AC-S outflow (depth: 11m); CTD samples with 5-6 depths were collected on upcast. b) vacuum pressure for filtration: maximum 200 hPa c) samples were shock frozen in liquid nitrogen and then stored in -80°C until measurement after cruise. d) blank filters were collected by soaking them in 0.2um filtered seawater. e) replicates were not collected. 2.

About measurements: a) Instrument: dual-beam UV/VIS Spectrophotometer (Cary 4000, Varian Inc., Palo Alto, CA, USA) equipped with a 150 mm integrating sphere (external DRA-900, Varian, Inc. and Labsphere Inc., made from Spectralon (TM)). b) wavelength range of scan and resolution: 300-850 nm, 1 nm. c) slit band width: 2 nm. d) scan speed: 150 nm min−1 e) Sample filters were extracted with 95% methanol for the absorption measurement of NAP. f) The baseline of the spectrophotometer was set with a dry piece of a blank filter.