Oral or Poster

IAPSO

P02 - Physics and Biogeochemestry of Semi-Enclosed, Shelf Seas and Coastal Zones

Heat flux interannual variability according to atmospheric reanalysis data in the Black Sea

Climate change and its impacts are becoming increasingly relevant in scientific research, particularly in the context of marine ecosystems state. The thermal structure of the Black Sea, as a semi-enclosed water body, is largely determined by heat fluxes across the air-sea boundary. This is due to its strong salinity stratification preventing deep vertical mixing. However, attempts to describe this structure based on the total heat flow or the study air-sea fluxes of climate-active gases are faced with a lack of in situ data. A common alternative approach for flux researches is the atmospheric reanalysis. Discrepancies in the estimates of fluxes from reanalysis remains unclear and could lead to false conclusions about the state of the ecosystem. This study focuses on a comparative analysis of heat fluxes and their components over the surface of the Black Sea for the period from 2011 to 2024 according to the NCEP CFSR v2 and ERA5 reanalysis. Both reanalysis provide information on atmospheric conditions, however, these reanalysis vary in terms of their temporal and spatial resolution, as well as the algorithms used for data assimilation and the volume of data incorporated during the assimilation process. These differences may result in significant discrepancies in the estimates of heat fluxes and wind velocity. The study provides an assessment of the total heat flux and its components: sensible and latent heat fluxes, as well as shortwave and longwave radiation. Heat fluxes were estimated across all basin as well as in a cross-section from shore to shore. This comparison was necessary to evaluate the differences between the central part and the coastal areas. The obtained results were compared with in situ data collected by the Shirshov Institute of Oceanology RAS (South branch) in the northeastern part of the Black Sea. Observations include measurements of the concentration of carbon dioxide in the air, as well as the parameters of the carbonate system in seawater, which is necessary for calculating the CO2 air-sea flux and monitoring of the sea thermal structure of the upper active layer. The results of our research underscore the importance of selecting the appropriate data source for assessing thermal and gas fluxes in the marine environment. These data serve for better understanding climate change in the Black Sea and its impact on the regional ecosystem state. This study was supported by state assignments FMWE-2024-0016 and FMWE-2023-0001.