F/S Polarstern cruise ARK-XXVI/3, also known as TransArc (Trans-Arctic survey of the Arctic Ocean in transition). From 5. August (Tromsö) to 7. October (Bremerhaven) a total of 1254 samples were analyzed from 56 stations. Seawater samples were sampled throughout the water column according to Dickson et al. (2007) and analyzed on board within hours. Data quality is discussed. Resulting data is correctable through the use of certified reference material (CRM), after which data is deemed to be of reasonably high quality. All samples and data were sampled, analyzed and processed by Adam Ulfsbo and Ylva Ericson (University of Gothenburg, Sweden).

The seawater carbonate chemistry was calculated using seacarb with parameters: TA, DIC, S, T and depth. The dissociation constants used were Dickson et al. (2007) recommend the formulations of Lueker et al. (2000) for carbonic acid, Perez and Fraga (1987) for hydrogen fluoride and Dickson (1990) for hydrogen sulphate.