Ocean Sci., 12, 937–951, 2016 www.ocean-sci.net/12/937/2016/ doi:10.5194/os-12-937-2016 © Author(s) 2016. CC Attribution 3.0 License. Aragonite saturation states and pH in western Norwegian fjords: seasonal cycles and controlling factors, 2005–2009 Abdirahman M. Omar1,2, Ingunn Skjelvan1, Svein Rune Erga3, and Are Olsen2 1Uni Research Climate, Bjerknes Centre for Climate Research, Bergen, Norway 2Geophysical Institute, University of Bergen, and Bjerknes Centre for Climate Research, Bergen, Norway 3Department of Biology, University of Bergen, Bergen, Norway Correspondence to: Abdirahman M. Omar (
[email protected]) Received: 26 February 2016 – Published in Ocean Sci. Discuss.: 17 March 2016 Revised: 29 June 2016 – Accepted: 30 June 2016 – Published: 26 July 2016 Abstract. The uptake of anthropogenic carbon dioxide March), when both pH and sea surface temperature (SST) are (CO2/ by the ocean leads to a process known as ocean acid- low and DIC is its highest. Consequently, seasonal Ar vari- ification (OA), which lowers the aragonite saturation state ations align with those of SST and salinity normalized DIC (Ar/ and pH, and this is poorly documented in coastal en- (nDIC). vironments including fjords due to lack of appropriate obser- We demonstrate that underway measurements of fugacity vations. of CO2 in seawater (f CO2/ and SST from VOS lines com- Here we use weekly underway data from the Voluntary bined with high frequency observations of the complete car- Observing Ships (VOS) program covering the period 2005– bonate system at strategically placed fixed stations provide 2009 combined with data from research cruises to estimate an approach to interpolate OA parameters over large areas in Ar and pH values in several adjacent western Norwegian the fjords of western Norway.