Abstract. A new atmospheric measurement station has been established on the North Sea oil and gas production platform F3, 200 km north off the Dutch coast (5°51' N, 4°44' E). Atmospheric concentrations of O₂ and CO₂ are continuously measured using fuel cell technology and compact infrared absorption instruments, respectively. Furthermore, the station includes an automated air flask sampler for laboratory analysis of the atmospheric concentrations of CO₂, CH₄, CO and O₂ and isotope measurements of δ¹³C, δ¹⁸O and Δ¹⁴C from CO₂. This station is the first fixed sea based station with on-site continuous O₂ and CO₂ measurements and therefore yields valuable information about the CO₂ uptake in coastal marine regions, specifically the North Sea. This paper presents the measurement station and the used methodologies in detail. In comparison to land-based stations, the data show low day-to-day variability, as they are practically free of nightly inversions as well as human influences, due to the station's remoteness. Therefore, the data set collected at this measurement station serves directly as background data for the coastal northwest European region. Additionally, the first data are presented showing the seasonal cycle as expected during August 2008 through June 2009. Furthermore, some short-term O₂ and CO₂ signals are presented. The observations at the platform include several large and fast changing negative atmospheric O₂ excursions without an accompanying change in the CO₂ signal, which most likely indicate marine O₂ uptake.