Figure 3
From: The Transpolar Drift conveys methane from the Siberian Shelf to the central Arctic Ocean
Salinity, fractions of freshwater components, i.e. sea-ice meltwater (fSIM) and river waters (fr) and methane saturation (top down) along the 60°E section (from north to south, section location see Fig. 1a) in 2015 (left) and 2011 (right). Fractions of freshwater components are based on mass balance calculations of salinity, nutrients and the stable oxygen isotope composition (δ18O) in the water column. The pronounced negative fractions of sea ice meltwater (fSIM) shows sea ice production with subsequent brine release, i.e. freezing, as the main process forming PSW in both years. Differences between both years are apparent at the southernmost part of the section. In 2011 negative fSIM cover the whole section with positive values just in the upper ~20 m showing the effect of melting. In 2015 positive (fSIM) values are found in the upper ~40 m in that region whereas below 40 m (fSIM) values close to zero reflect the negligible sea ice influence on inflowing AW. Fractions of meteoric waters (fr) primarily reflect the influence of river waters released to the Siberian shelves and transported via the TDS. The influence of river water is mostly limited to the northern part of the section and is much smaller in 2011 compared to 2015. Whereas the huge methane super-saturation in 2011 is unaffected by river water, the moderate super-saturation in 2015 may have contributions from several sources, i.e. freezing, melting and methane from river water discharge.
