| Summary: | The study sites included six different fjords located in an area spanning from 56.6˚N to 66.6˚N and from −39.0˚W to 13.7˚E. All data were collected throughout five cruises from April to July 2023, with instruments installed on R/V Skagerak (University of Gothenburg). N 2 O dissolved in the surface water was measured continuously via Cavity Enhanced Absorption Spectroscopy using a LI-7820 N 2 O/H 2 O trace gas analyzer (LI-COR Biosciences). The LI-7820 produced high-precision N 2 O (ppb) measurement data every second, response time of 0 to 330 ppb ≤ 2 seconds and a maximum drift of < 1 ppb per 24-hour period. LI-7820 recorded timestamped measurements (>1800 measures were recorded in each fjord) were subsequently averaged (integrated) over 30 min to make data analysis feasible (Table 1). N 2 O measurements were then adjusted by pushing back the data by 20 minutes to account for headspace equilibration response time and for the time it takes to the water to travel from the sea to the exchanger itself. The ship was equipped with a -4H-FerryBox (JENA Engeneering GmbH, Germany), an automatic flow-through system with various sensors measuring hydrographic and biochemical parameters such as s alinity, temperature, dissolved oxygen (O 2 ), pH, chlorophyll, and turbidity (-4H-JENA engineering GmbH, n.d.). All potentiometric FerryBox pH (EGA150, Meinsberg) measurements on the NBS scale were corrected by a constant offset (ΔpH = -0.451 ±0.016) based on the concurrent spectrophotometric pH measurements (Müller et al., 2018) during the Greenlandic and Icelandic cruises. Water was pumped through a subsurface inlet and circulated at 1 m s −1 in the system. Bubbles and particles are removed by a debubbling unit (Ferry- Box Task Team, n.d.). Windspeed (m s −1 ) measurements were recorded with an onboard sonic anemometer (Airmar PB200) mounted approximately 19 meters above the water line and then logarithmically corrected to 10 meters above the water line. Additionally, water samples for dissolved nitrates and nitrites (NO x ...
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