Long-term Variations in Heat Storage in the South-eastern Mediterranean Sea

Heat storage (HS) plays an essential role in the dynamic of oceans and seas. Hence, it is important to examine the behaviour of change in the HS at the different water layers; as this may have impact on other ocean processes and biotic systems. This study attempts to investigate the long-term variations in the HS at the upper 100 and 300 m layers in the south-eastern Mediterranean region. It depends on hydrographic data (temperature and salinity) collected over the period 1948-2021. The examination of trends was carried out using the linear regression approach for the calculated HS. Results revealed a significant decreasing annual trend of -3.94E6 Jm-2/yr at the 100 m-layer, and a non-significant decreasing trend of -0.0037E9 Jm-2/yr at the 300 m-layer. The quadratic regression approach was used to assess any cyclicity in the HS. Results revealed cyclic behaviour of changes in HS at the two layers of interest, but with different minimum years of occurrence. While at the 100 m-layer the minimum year of occurrence was 1992, it was 1989 at the 300 m-layer. This may be attributed to both the dynamical processes taken place at each layer and to the criteria of the water masses spreading over the different depths in the south-eastern Mediterranean region. Further investigation on the relationship between HS and other biotic features in the south-eastern Mediterranean region is still needed. Keywords: heat storage, cycles, trends, South-eastern Mediterranean