Seasonal and interannual variability of the water exchange in the Turkish Straits System estimated by modelling

Abstract

A chain of simple linked models is used to simulate the seasonal and interannual variability of the Turkish Straits System. This chain includes two-layer hydraulic models of the Bosphorus and Dardanelles straits simulating the exchange in terms of level and density difference along each strait, and a one-dimensional area averaged layered model of the Marmara Sea. The chain of models is complemented also by the similar layered model of the Black Sea proper and by a one-layer Azov Sea model with the Kerch Strait. This linked chain of models is used to study the seasonal and interannual variability of the system in the period 1970-2009. The salinity of the Black Sea water flowing into the Aegean Sea increases by approximately 1.7 times through entrainment from the lower layer. The flow entering into the lower layer of the Dardanelles Strait from the Aegean Sea is reduced by nearly 80% when it reaches the Black Sea. In the seasonal scale, a maximal transport in the upper layer and minimal transport in the bottom layer are during winter/spring for the Bosphorus and in spring for the Dardanelles Strait, whereas minimal transport in upper layer and maximal undercurrent are during the summer for the Bosphorus Strait and autumn for the Dardanelles Strait. The increase of freshwater flux into the Black Sea in interannual time scales (41 m3s-1 per year) is accompanied by a more than twofold growth of the Dardanelles outflow to the North Aegean (102 m3s-1 per year).

Circulation of the Turkish Straits System under interannual atmospheric forcing

“…Climatological means of water and tracer fluxes through the TSS were initially estimated from long-term observations of seawater properties at junctions of the straits and on surface water fluxes (Ünlüata et al, 1990;Beşiktepe et al, 1994;Tugrul et al, 2002;Maderich et al, 2015), followed later by ship-borne and moored acoustic Doppler current profiler (ADCP) measurements at the straits (Özsoy et al, 1988, 1998Altıok et al, 2012;Jarosz et al, 2011bJarosz et al, , a, 2012Jarosz et al, , 2013. Updated reviews of TSS fluxes based on combined data have been provided by Schroeder et al (2012), Özsoy and Altıok (2016), Sannino et al (2017) and Jordá et al (2017).…”

“…Simplified two-layer or laterally averaged models of the Dardanelles and Bosphorus were later developed by Oguz and Sur (1989), Stashchuk and Hutter (2001) and Oguz et al (1990), respectively, while Hüsrevoglu (1998) introduced a 2-D reduced gravity ocean model of the Dardanelles inflow into the Sea of Marmara. Similar 2-D laterally averaged models (Maderich and Konstantinov, 2002;Ilıcak et al, 2009;Maderich et al, 2015) and 3-D models (Kanarska and Maderich, 2008;Öztürk et al, 2012), which were of limited extent, have been used to construct simplified solutions for the Bosphorus exchange flows. Bosphorus hydrodynamics were extensively investigated by Sözer and Özsoy (2017a) using a 3-D model with turbulence parameterisation under idealised and realistic topography with stratified boundary conditions in adjacent basins, demonstrating the unique hydraulic controls in the maximal exchange regime that are to be established in the realistic case.…”

Assessment of the water fluxes from the Blach Sea to the Mediterranean using a HF radar

“…The outflow fluxes of the Dardanelles to the Aegean in the upper layer were estimated in subchapter 5.1. The estimations (of transect 3) are compared with the works of Tuğrul et al, 2002, Kourafalou andBarbopoulos (2003), Beşiktepe et al, (2008) Kanarska and Maderich (2008), Androulidakis (2011), Jarosz et al, (2013 and Maderich et al, (2015). Our results are comparable and in a good agreement for Winter and Autumn but we are clearly underestimate the fluxes during Summer and Spring.…”

Circulation of the Turkish Straits System between 2008–2013 under complete atmospheric forcings

“…Climatological means of water and tracer fluxes through the TSS were initially estimated from long-term observations of seawater properties at junctions of the straits and on surface water fluxes Beşiktepe et al, 1994;Tugrul et al, 2002;Maderich et al, 2015), followed later by ship-borne and moored ADCP measurements at the straits (Özsoy et al, 10 1988; Özsoy et al, 1998;Altıok et al, 2012;Jarosz et al, 2011bJarosz et al, , a, 2012Jarosz et al, , 2013. Updated reviews of TSS fluxes based on combined data have been provided by Schroeder et al (2012); Özsoy and Altıok (2016); Sannino et al (2017); Jordá et al (2017).…”

“…Simplified two-layer or laterally averaged models of the Dardanelles and Bosphorus were later developed by Oguz and Sur (1989), Stashchuk and Hutter (2001) and Oguz et al (1990) respectively, while Hüsrevoglu (1998) introduced a 2D reduced gravity ocean model of the Dardanelles inflow into the Marmara Sea. Similar 2D laterally averaged models (Maderich and Konstantinov, 2002;Ilıcak et al, 2009;Maderich et al, 2015) and 3D models (Kanarska and Maderich,30 2008; Öztürk et al, 2012), which were of limited extent, have been used to construct simplified solutions for the Bosphorus exchange flows. Bosphorus hydrodynamics were extensively investigated by Sözer and Özsoy (2017a) using a 3D model with turbulence parameterisation under idealised and realistic topography with stratified boundary conditions in adjacent basins, demonstrating the unique hydraulic controls in the maximal exchange regime that are to be established in the realistic case.…”