Inter-basin Exchange Fluxes

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Climatological estimates of water fluxes based on water and salt budgets of the TSS coupled with the Black Sea have been given in Ünlüata et al. (1990), Beşiktepe et al. (1993, 1994), Tuğrul et al. (2002), followed later by ship-borne and moored ADCP measurements at the straits (Özsoy et al., 1988; Özsoy et al., 1998; Altıok et al., 2012; Jarosz et al., 2011a,b, 2012, 2013). The influence on the Mediterranean Sea overall budgets have been reviewed in Schroeder et al. (2012), Mavropoulou et al. (2016), Jordà et al. (2016), while the influence on the Black Sea budget has been reviewed by Özsoy and Ünlüata (1997, 1998); Peneva et al. (2001); Kara et al. (2008).The net flux, which is the difference between the upper and layer fluxes, is estimated to be comparable to the Black Sea river runoff, since the annual average precipitation and evaporation over the sea surface are roughly of the same order and often considered to cancel each other (Özsoy and Ünlüata, 1997, Kara et al., 2008).

Instantaneous measurements of Bosphorus fluxes from ship mounted ADCP (Özsoy et al. 1996, 1998) have yielded statistical average fluxes the upper and lower layers, found to have great variability confirmed by the later measurements of Jarosz et al. (2011a,b, 2012, 2013). The variability in observed currents in the Bosphorus and Dardanelles Straits, from daily to inter-annual time scales have also been shown by recent assessments of CTD-based hydrographic and ADCP-based flux measurements (Özsoy and Altıok,2016a,b), as also evaluated by Sannino et al. (2017). Mean values of the upper, lower layers and the total flux, respectively, were provided at the ends of the Bosphorus and Dardanelles Straits based on 6 months to a year of continuous measurements (Jarosz et al. 2011a,b, 2013). These measurements confirmed the great variability in fluxes, but showed noticeable differences of the net fluxes between any two sections, posing questions of statistical reliability. The average volume fluxes computed from the 10 years of monthly measurements campaign of Altıok and Kayışoğlu (2015) have resulted in mean upper, lower layer and net fluxes of the Bosphorus Strait in agreement with earlier measurements. In these measurements, the net flux seemed to be better conserved between the two ends of the Strait, also showing a small decreasing trend in fluxes over the period of 10 years.

The net flow out of the Black Sea implies a sea level response with the Black Sea being about a fraction of a meter higher than the Aegean Sea, with short-term to inter-annual variability (Möller, 1928; Bogdanova, 1969; Gunnerson and Özturgut, 1974; Büyükay, 1989; Özsoy et al.,1998; Alpar et al., 2000; Tutsak, 2012; Tutsak et al., 2016).

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