Abstract Straits, as conduits for the exchange of physical and biogeochemical properties of water masses, control mass and momentum transport between large water bodies where boundaries have a fundamental impact on the flow. The Turkish Strait System (TSS), that is, the Istanbul and the Canakkale (a.k.a, Bosphorus and Dardanelles) Straits and the Sea of Marmara (SoM) carry the brackish surface waters of the Black Sea and the salty deep Mediterranean Sea waters via a spatiotemporally varying two‐layered exchange. Climate change influences the vertical exchange between these layers, as well as the barotropic and baroclinic transport between the neighboring seas of the TSS. Salinity and current profiles from past surveys between 1985 and 2023 at the strait‐ends are used to calculate water and salt budgets for each layer in the TSS at seasonal time‐scales. For the first time, monthly volume and salt fluxes across the TSS are quantified based on multidecadal salinity changes. The analysis shows that over the past decade, warmer and saltier water masses have entered the TSS from its ends, decreasing the net transport. The layered fluxes show strong seasonality, with surface and bottom layer fluxes being more sensitive to the salinity changes in the first and second halves of the year, respectively. The interfacial layer stratification have decreased across the TSS. The potential implications of the change in exchange flows are identified as slower thermohaline circulation in the Mediterranean Sea, reduced oxygen transport for the deep ventilation in the Black Sea, and oxygen depletion in the SoM.
Basdurak et al. (Sun,) studied this question.