Observation of Oxygen-18 in Ocean Waters in the Vicinity of Iceland

The goal of the present project is to use oxygen-18 to map water masses North of Iceland. Here we report on findings from field campaigns carried out over the period from 1988 to 2019. The samples were collected on Icelandic vessel cruises from waters that currents bring from the south and from the north and are found west and north of Iceland.  An emphasis was placed on low salinity waters that characterize the Polar Water of the East Greenland Current. The data cover all seasons and a salinity range from 29.1 to 35.3.  The observations generally also include biogeochemical constituents: dissolved oxygen and the nutrients phosphate, nitrate, and silicate (Olafsson, Olafsdottir et al. 2010).    Oxygen isotope measurements were carried out at the Science Institute, University of Iceland. Prior to 2007 we used a Finngan MAT 251 Mass-spectrometer and extracted oxygen from the water by equilibrating degassed water with a small amount of CO2 gas (Epstein and Mayeda, 1953). After 2007 the measurements were performed on a continuous flow Delta V Advantage mass-spectrometer, with a Gas bench device. The accuracy of the measurements is better than 0.05‰.  We examine the δ18O -S relationships for variations with seasons and time. The surface waters of the observed regions are seasonally productive but with different winter nutrient concentrations to support phytoplankton spring blooms. We examine variations in the seasonal δ18O-nutrient relationships.   Epstein, S. and Mayeda, T.K. (1953). Variation in O18 content of waters from natural sources. Geochim Cosmochim. Acta 4:213-224.  Olafsson, J., S. R. Olafsdottir, A. Benoit-Cattin and T. Takahashi (2010). "The Irminger Sea and the Iceland Sea time series measurements of sea water carbon and nutrient chemistry 1983–2008." Earth Syst. Sci. Data 2(1): 99-104.