Basin-Scale Observations of Monoterpenes in the Arctic and Atlantic Oceans

We report novel in situ speciated observations of monoterpenes (α- and β-pinene, myrcene, δ3-carene, ocimene, limonene) in seawater and air during three cruises in the Arctic and Atlantic Oceans, in/over generally oligotrophic waters. Oceanic concentrations of the individual monoterpenes ranged from below the detection limit of <1 pmol L^-1 to 5 pmol L^-1, with average concentrations of between 0.5 and 2.9 pmol L^-1. After careful filtering for contamination, atmospheric mixing ratios varied from below the detection limit (<1 pptv) to 5 pptv, with averages of 0.05-5 pptv; these levels are up to 2 orders of magnitude lower than those reported previously. This could be at least partly due to sampling over waters with much lower biological activity than in previous studies. Unlike in previous studies, no clear relationships of the monoterpenes with biological variables were found. Based on our measured seawater concentrations and a global model simulation, we estimate total global marine monoterpene emissions of 0.16 Tg C yr^-1, similar to a previous bottom-up estimate based on laboratory monoculture studies but 2 orders of magnitude lower than a previous top-down estimate of 29.5 Tg C yr^-1.