Oxygen isotope-salinity relation in an Arctic fjord (Kongsfjorden): Implications to hydrographic variability

Abstract

The global warming leads to a large freshwater influx into the Arctic Ocean, which has adverse implications to the sea-ice dynamics, ocean circulation, and acidification. The relationship between oxygen isotope ratio (δ18O) and salinity (S) is helpful in exploring various hydrographic processes related to the freshwater influx and is also required to accurately determine past salinity variability using oxygen isotope ratio of the carbonates. In view of this, systematic measurements of δ18O and salinity of water from an Arctic fjord (Kongsfjorden) were carried out during the summer season of 2013. Until now, the relationships between δ18O and salinity from such fjords were based on a limited number of samples collected during a very short span of time and thus may not accurately represent the long-term conditions prevailing in the fjord. The present study determines a more representative δ18O–salinity relationship as water samples from different depths and location over a long period were systematically collected. The water samples were collected from four different locations at different depths along the axis of the fjord representing the inner and outer fjords. The inner stations (I-8 and I-6) exhibit lower δ18O values than the outer stations (I-1 and I-3), which indicate the higher influence of freshwater from glacial melting in the inner stations. The δ18O–salinity relationship from the inner and outer fjords yield a slope of 0.54 (r2 = 0.67, n = 56) and 0.39 (r2 = 0.66, n = 68), respectively. The δ18O of freshwater influx in the fjord is estimated at –18.4‰, which is close to the widely accepted freshwater-δ18O value of the Arctic basin. The δ18O of glacial discharge, which is the largest source of freshwater influx to the fjord, is estimated at ca. –21.0‰, which will be useful for future freshwater budget calculations. Keywords: Arctic, Fjord, Oxygen isotopes, Salinity, Freshwater, Melting