Semeryuk, Irina (2011) Identification of Sea Ice Derived Brine Signals from the Siberian Shelf areas Based on Stable Oxygen Isotope and Salinity Data along the Siberian Continental Margin Obtained during NABOS Cruises (2005-2009). (Master thesis), State University of St. Petersburg, Russia ; University of Hamburg, St. Petersburg, Russia, 105 pp.

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Abstract

The major aim of this study is to analyze datasets of δ18O and salinity from the Arctic shelf seas in order to quantify sea-ice melt water fraction (fi) and river runoff fraction (fr) added to the water column from the Siberian shelf seas. Interpretation and comparison of data obtained in different years allows to relate temporal and spatial changes in water temperature, salinity and δ18O content to the shelf-basin exchange processes. The relationship between salinity, temperature, and δ18O content allows to identify the source and conditions of formation of local water types, including Surface Mixed Layer (ML), Cold Halocline Water (CHW), warm Atlantic Water (AW) and to estimate the extent of mixing between these waters.
The data used in this Master thesis were collected during the icebreaker expeditions NABOS (Nansen and Amundsen Basin Observation System) in the Eurasian Basin (August – September 2005-2009). Water samples were taken at the standard levels ( 10, 25, 50, 75, 100, 150, 200, 250, 300, 350, 400, 500 m last depth level depends on expedition) for δ18O, dissolved oxygen, salinity, nutrient measurements using a rosette system equipped with 5 l Niskin bottles during each cruise. Water samples intended for δ18O analysis were collected in glass bottles in order to prevent evaporation which would be considerable higher through the walls of plastic containers. A total of 233, 437, 409 samples were taken during the 2005, 2006, 2008 NABOS expeditions respectively (Dmitrenko I. et al., NABOS-05-09 reports, 2005-2009). Samples for δ18O were analyzed at the Stable Isotope Laboratory of the Alfred Wegener Institute, Germany, Geoscience Isotope Laboratory of the British Geological Survey, UK, the Leibniz Laboratory Kiel, Germany in 2009, 2008, 2005-2007 respectively. The precission of analytical measurements for all laboratories is ± 0.03.
The isotope-tracer method has been used successfully in polar circulations studies where H2180-deficient fresh water from river runoff can be distinguished from the fresh water influence of melting sea-ice (Östlund and Hut, 1984; Bauch D. et al., 1995; Ekwurzel et al., 2001). By examining the relationship between H2180, salinity, and temperature, it is also possible to identify the source and conditions of formation of local water types and assess quantitatively the extent of mixing between these waters.

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