The Arctic shelf regions as a source of freshwater and brine-enriched waters as revealed from stable oxygen isotopes

The water masses of the Arctic Ocean shelf regions are significantly influenced by river water and sea-ice processes. Since river water is highly depleted in ∂18O relative to marine waters as well as to sea-ice, the ∂18O composition and salinity of a water sample can be used to separate the different freshwater water sources. In this paper the distributions of river water, sea-ice melt water or sea-ice formation are discussed for the Kara, Laptev and Beaufort shelves based on ∂18O and salinity data. Depending on the average depth the observed fields of salinity and ∂18O values are different for each region. But comparing the overall ∂18O and salinity correlations reveals a remarkable similarity for these three Arctic shelf regions as similar local bottom-water masses are formed by sea-ice processes. Remnants of these seaice derived bottom water masses are found on all shelves during summer at a salinity of about 30. Investigations at the shelf break of the Kara Sea and Laptev Sea show that river water as well as brine waters are exported to the Arctic Ocean halocline. This export shows inter-annual variability in correlation with wind forcing during summer