The focus of the presented study is the variability of the hydrology of the Laptev Sea. The study analyses results from three-dimensional coupled ice-ocean regional models of different horizontal resolutions. The Laptev Sea circulation and its inter-annual variability are simulated on the basis of a large-scale model of the Arctic and North Atlantic. The second model is a nested ocean model focused on the Lena River Delta surroundings with an enhanced grid resolution. Both models are forced by the NCEP/NCAR Reanalysis. The simulated high variability of summer circulation over the Laptev shelf is mainly caused by the difference in the local prevailing wind patterns. The analysis of the Lena river model tracer pathways shows that in summer, the pronounced offshore or onshore transport occurs in certain years, while generally, the circulation pattern is much more complicated being subject to wind forcing, position of the ice edge, and intensity of the river runoff. When the cyclonic circulation of the atmosphere is predominant, the heat and fresh water anomalies, formed due to the sea surface fluxes and the river runoff, penetrate down to the bottom layers. The model results suggest that the response of winter hydrography to the variability of atmospheric circulation is less pronounced. The salinity pattern, formed during the autumn period under the influence of the wind, persists for a long period during winter and gradually changes under the influence of sea-ice formation processes and on contact with the adjacent water areas. Our simulations show that there was a possibility of a pronounced increase in the near-bottom temperature in the Laptev Sea shelf. The heat flux of the Lena River plays a significant role in this process. The warming of near-bottom waters on the Laptev Sea shelf deserves special attention due to its potential impact on the submarine permafrost, formed during the last glacial cycle, when the Arctic shelf was above sea level. We have performed numerical simulations of the subsea permafrost evolution and the present-day state on the East Siberian Arctic Shelf, using near-bottom temperature provided by the ice-ocean model. Our simulation estimates that the thickness of the permafrost within most of the shelf is 180-550 m, given the geothermal flux value of 60 mW m -2 . These results show the permafrost upper boundary deepening by ~0.5-5 m from 1948 to 2014 (≤7.5 cm yr -1 ) in the shelf. The degradation rate from above is the most rapid in the near-shore coastal zone of the shelf and in the areas affected by the Lena River outflow. Based on the simulations performed, we state that the current warming is not able to destabilize undersea permafrost on the shelf of the Laptev Sea.