Abstract.A new system for continuous, highly resolved oceanic and atmospheric measurements of N 2 O, CO and CO 2 is described. The system is based upon off-axis integrated cavity output spectroscopy (OA-ICOS) and a nondispersive infrared analyzer (NDIR), both coupled to a Weiss-type equilibrator. Performance of the combined setup was evaluated by testing its precision, accuracy, long-term stability, linearity and response time. Furthermore, the setup was tested during two oceanographic campaigns in the equatorial Atlantic Ocean in order to explore its potential for autonomous deployment onboard voluntary observing ships (VOS). Improved equilibrator response times for N 2 O (2.5 min) and CO (45 min) were achieved in comparison to response times from similar chamber designs used by previous studies. High stability of the OA-ICOS analyzer was demonstrated by low optimal integration times of 2 and 4 min for N 2 O and CO respectively, as well as detection limits of < 40 ppt and precision better than 0.3 ppb Hz −1/2 . Results from a direct comparison of the method presented here and well-established discrete methods for oceanic N 2 O and CO 2 measurements showed very good consistency. The favorable agreement between underway atmospheric N 2 O, CO and CO 2 measurements and monthly means at Ascension Island (7.96 • S 14.4 • W) further suggests a reliable operation of the underway setup in the field. The potential of the system as an improved platform for measurements of trace gases was explored by using continuous N 2 O and CO 2 data to characterize the development of the seasonal equatorial upwelling in the Atlantic Ocean during two R/V Maria S. Merian cruises. A similar record of high-resolution CO measurements was simultaneously obtained, offering, for the first time, the possibility of a comprehensive view of the distribution and emissions of these climate-relevant gases in the area studied. The relatively simple underway N 2 O/CO/CO 2 setup is suitable for long-term deployment onboard research and commercial vessels although potential sources of drift, such as cavity temperature, and further technical improvements towards automation, still need to be addressed.

A new system for continuous, highly-resolved oceanic and atmospheric measurements of N₂O, CO and CO₂ is described. The system is based upon off-axis integrated cavity output spectroscopy (OA-ICOS) and a non-dispersive infrared analyzer (NDIR) both coupled to a Weiss-type equilibrator. Performance of the combined setup was evaluated by testing its precision, accuracy, long-term stability, linearity and response time. Furthermore, the setup was tested during two oceanographic campaigns in the equatorial Atlantic Ocean in order to explore its potential for autonomous deployment onboard voluntary observing ships (VOS). Improved equilibrator response times for N₂O (2.5 min) and CO (45 min) were achieved in comparison to response times from similar chamber designs used by previous studies. High stability of the OA-ICOS analyzer was demonstrated by low optimal integration times of 2 and 4 min for N₂O and CO respectively, as well as detection limits of < 40 ppt and precision better than 0.3 ppb Hz^−1/2. Results from a direct comparison of the method presented here and well-established discrete methods for oceanic N₂O and CO₂ measurements showed very good consistency. The favorable agreement between underway atmospheric N₂O, CO and CO₂ measurements and monthly means at Ascension Island (7.96° S 14.4° W) further suggests a reliable operation of the underway setup in the field. The potential of the system as an improved platform for measurements of trace gases was explored by using continuous N₂O and CO₂ data to characterize the development of the seasonal equatorial upwelling in the Atlantic Ocean during two R/V Maria S. Merian cruises. A similar record of high-resolution CO measurements was simultaneously obtained offering for the first time the possibility of a comprehensive view on the distribution and emissions of these climate relevant gases on the area. The relatively simple underway N₂O/CO/CO₂ setup is suitable for long-term deployment on board of research and commercial vessels although potential sources of drift such as cavity temperature and further technical improvements towards automation still need to be addressed