Turbulent heat fluxes in the Barents Sea in the 20th and 21 st centuries based on the ensemЫe of CMIP6 models

Abstract

The Barents Sea has experienced the highest near-surface air temperature growth rates on Earth in recent decades, mainly due to а significant reduction in sea ice area in winter. In the sea area, there is an intensive heat exchange between the ocean and the atmosphere, which is modulated Ьу the changes in the sea ice area. The turbulent fluxes of sensiЫe and latent heat are the most sensitive to changes in the ice cover. It is important to tak:e into account the aЬility of СМIРб global climate models to reproduce turbulent fluxes, as well as the cross-model variation of results, when assessing the uncertainty of Arctic climate proj ections in the 21 st century. In the paper, the variaЬility of turbulent heat fluxes in the Barents Sea is analyzed over the period 1980-2100 based on the СМIРб project's ensemЫe of climate models for the anthropogenic impact scenarios SP245 and SSP585, and the relationships are identified with their defining climatic characteristics: sea ice area, sea surface temperature, near-surface air temperature, and surface wind velocity. It is f ound that the latent heat flux from the ocean to the atmosphere increases in September until 2070, after which the changes plateau. This feature of the latent heat flux is explained Ьу the synchronous decrease of the sea ice area in the Barents Sea to zero values Ьу 2070. In March, with а steady decrease of the sea ice, а linear increase in the latent heat flux is observed since Ьу the end of the 21 st century the sea ice area will remain approximately at the level of the September values of the l 980s. The sensiЫe heat flux is characterized Ьу pronounced nonlinearity: in March, it increases to 40 W /m2 Ьу the middle of the century, and then decreases to 30 W/m2 (the 1980 level) Ьу 2100; in September, it decreases after 2040. This is due to а more rapid increase in the near-surface air temperature compared to the sea surface temperature, which reduces the vertical temperature gradient and, as а consequence, heat flux from the sea surface, especially in the second half of the 21 st century. For the multi-model ensemЫe mean values, it was found that in March the maximum sensiЫe heat flux is observed when the Barents Sea is covered Ьу continuous ice cover at а level of 2-4x l 05 km2 (15-30% of the sea surface), whereas in September, the maximum sensiЫe heat flux values are observed in the sea ice area range of 0.5-1х105 km2• At the same time, in the historical period of the late 20th and early 21 st centuries, the СМIРб models underestimate the sensiЫe and latent heat fluxes in winter relative to the ERA5 climate reanalysis, but slightly overestimate them in summer, with а threefold smaller inter-model scatter in summer ( cr = 3-4 W /m2) relative to winter (cr = 12-13 W/m2).