Figure 4

Sea ice drift trajectories leading to the 60°E section and δ¹⁸O isotopic composition (filled symbols) and salinity (open symbols) in sea ice at this section. Backward drift trajectories from the 60°E section show the sea ice formation areas, i.e. off shore within the Laptev Sea and in the coastal polynya areas. Trajectories were calculated based on a combination of sea ice motion and concentration products from passive microwave satellite data. The colour of the end node indicates the source area of sampled sea ice. Trajectories with red end nodes were formed in polynyas, namely the New Siberian (NS) Polynya, Taymyr (T) Polynya, Northeastern Taymyr (NET) Polynya and East Severnaya Zemlya (ESZ) Polynya. Grey end nodes refer to trajectories that were formed during freeze-up further offshore. The colour coding of the start node characterizes the month of formation (primarily October) of the individual trajectories. The δ¹⁸O ice isotopic composition reflects the δ¹⁸O composition of the water column from which each segment of the ice core was formed. Light values below about −4‰ indicate formation in coastal polynyas while values above −2‰ indicate freeze-up formation offshore. Salinity of the ice cores is in all cases below 4. The map is generated with IDL (Interactive Data Langue), software for analysis and visualization of data provided by Harris Geospatial Solutions (http://www.harrisgeospatial.com).