High-frequency, year-round time series of the carbonate chemistry in a high-Arctic fjord (Svalbard)

Abstract. The Arctic Ocean is subject to high rates of ocean warming and acidification, with critical implications for marine organisms as well as ecosystems and the services they provide. Carbonate system data in the Arctic realm are spotty in space and time and, until recently, there was no time-series station measuring the carbonate chemistry at high frequency in this region, particularly in coastal waters. We report here on the first high-frequency (1 h), multi-year (5 years) dataset of salinity, temperature, dissolved inorganic carbon, total alkalinity, CO₂ partial pressure (pCO₂) and pH at a coastal site (11 m) in a high-Arctic fjord (Kongsfjorden, Svalbard). We show that (1) the choice of formulations for calculating the dissociation constants of the carbonic acid remains unsettled for Arctic waters, (2) the water column is generally somewhat stratified despite the shallow depth, (3) the saturation state of calcium carbonate is subject to large seasonal changes but never reaches undersaturation (Ω_a ranges between 1.4 and 3.0) and (4) pCO₂ is lower than atmospheric CO₂ at all seasons, making this site a sink for atmospheric CO₂ (16.8 mol CO₂ m⁻² yr⁻¹).