Sensitivity of the bottom layer temperature of the Arctic shelf seas to air temperature in the 20th–23rd centuries according to CMIP6 data

Sensitivity of the seafloor temperature (TB) of the Arctic shelf seas to changes in surface air temperature (TA) for the period of 1850–2300 was studied, based on the results of five models from the CMIP6 ensemble (Coupled Models Intercomparison Project, phase 6) under a scenario with high anthropogenic greenhouse gas emissions. The analysis is carried out in terms of ensemble statistics rather than individual models. Changes of both variables were calculated as a difference of mean values of the corresponding variable between pre-selected time intervals. These intervals characterized the pre-industrial state (1850–1900), modernity (2005–2015), the end of the 21st century (2090–2100), and the end of the 23st century (2290–2300). For the period of 2005–2015 the seas of the Siberian and North American shelves showed the sensitivity coefficients ∆TB/∆TA (∆ indicates changes relative to the pre-industrial period) less than 0,1 for average annual and winter values and up to 0.4 in summer. The results obtained for the summer period are in good agreement with available measurement data for the East Siberian shelf. The sensitivity coefficients for the Barents Sea during the period are higher, i. e. 0,17–0,44 for average annual values and from 0,4 to 0,6 for summer temperatures. Sensitivity coefficients for the 21st–23rd centuries show a significant increase, especially for the part of the Arctic shelf which would be free from ice. This is most pronounced for the summer period in the seas of the Siberian and North American shelves, where the regionally averaged values of sensitivity coefficients were up to 0,5 from pre-industrial values by the end of the 21st century and increased to 0,8 by the end of the 23rd century. For the last change in state, the sensitivity coefficient in summer in the Barents Sea sector was close to one. Analytical approximations of these dependencies are suggested, which allow calculations to be carried out using a model of thermophysics of the bottom shelf sediments.