In the present study we report hydrological (T and S) and hydrochemical data obtained during a Russian Trans-Arctic cruise in 2000 onboard the Hydrographic Vessel (HV) Nikolay Kolomeytsev, and describe the top layer of the sediment (a typical sample was taken from the upper 0--5 cm layer of bottom sediment) and the distribution of the organic carbon (δ13Corg) and nitrogen (δ15Norg) isotope ratios. Using both historical water data and data from our cruise, we divide the ESS into two specific areas: the Western area, influenced strongly by Lena River input, and the Eastern area, under direct influence of Pacific-derived water. We also used the stable δ13Corg and δ15Norg isotopes to detect the sediment geochemical boundary (or geochemical FZ) between Pacific marine-derived sediments and terrestrial derived sediments which can be considered to reflect the long-term (on a scale of 102 years) position of the most westward extension of Pacific water. These are among the first reliable hydrological and geochemical data reported for the ESS from the Dmitry Laptev Strait to the Long Strait, and they reveal novel insights about interaction between Pacific water and local shelf water.