Ozone and iodide measurements from the Atlantic Meridional Transect cruise AMT29 (DY110) between the 13th October 2019 and the 23rd November 2019.

This dataset includes Ozone uptake efficiency (OUE) in underway surface seawater and 1000 m deep seawater collected by CTD Niskin bottle; Dissolved iodide concentration in underway surface seawater; and Atmospheric ozone mixing ratio. Samples were collected during the Atlantic Meridional Transect cruise AMT29 (DY110), a trans-Atlantic cruise from Southampton, UK to Punta Arenas, Chile, between the 13th October 2019 and the 23rd November 2019. For OUE measurements, fresh, unfiltered underway seawater (from ~5.5 m below the surface) was continuously flushed into an overflowing, narrow-necked glass sample bottle. Occasional discrete water samples from 1000 m depth were also collected into 2 L glass bottles from the polypropylene Niskin bottles attached to a CTD. For Iodide measurements, discrete daily water samples (50 mL) were taken from the ship’s underway system, filtered (through GF/F filter paper using a glass syringe), and frozen (-20 °C) during the cruise for post-cruise iodide analysis using cathodic stripping square wave voltammetry (following Chance and Tinel et al. 2020). The contribution of iodide towards OUE was determined in post-cruise experiments by measuring iodide standards at different concentrations. Atmospheric measurements were conducted on the meteorological mast.