| Summary: | This set contains a data on ionic composition of the interstitial water of bottom sediments and subsea permafrost as an indicator of the sedimentation and sea water spreading within thawed strata. Based on measurements of concentration of sodium (Na+), potassium (K+), calcium (Ca2+), and magnesium (Mg2+) cations, chlorides (Cl–) and sulphates (SO42–) in water extracts from bottom sediments and subsea permafrost deposits from three boreholes a spatial difference in salinisation dynamics of thawed strata within the Buor-Khaya Bay was shown. A significant difference between permafrost and unfrozen sections was recorded. The vertical pattern of the macroions in the unfrozen segment was formed under the influence of subsea thawing of permafrost, while the permafrost section was formed under freshwater conditions and evolved under the thawing, and consequent sea water spreading. The significant compositional irregularity of ionic compositional patterns in the thawed deposits is caused by differences in the particle size of sediments and hydrodynamics of the Arctic basin, and also can be explained by Quaternary eustatic events on the East Siberian Arctic shelf. Lithology, grain size and hydrological regime were considered to be the most important factors controlling concentration of sea water salt to thawed sediments. Over the roof of subsea permafrost in the Ivashkina Lagoon, the pronounced salinity maximum (50 g/L of Cl–) of interstitial water was observed. Consisting of moss debris, this segment promotes the accumulation of dissolved pore water compounds due to its high porosity and subsequent thawing of frozen rock.
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