istjeo4 Aralik 2014

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The Leading Role of the Turkish Straits System in Ocean Science
and the Environmental Degradation Imposed on
Unique Natural-Cultural Heritage by Canal İstanbul
Türk Boğazlar Sistemi’nin Denizbilim’deki Öncü Rolü ve
Eşsiz Doğa-Kültür Mirası Karşısında Kanal İstanbul Çevre Katliamı
Emin Özsoya, Adil Sözera, Özgür Gürsesa, Ersin Tutsaka, Murat Gündüza,*, Gianmaria Sanninob
aInstitute of Marine Sciences, METU, PK 28, Erdemli, Mersin
*present address: Institute of Marine Sciences and Technology, DEÜ, İzmir
bENEA, via Anguillarese 301, 00123, Rome, Italy
(ozsoy@ims.metu.edu.tr)
Abstract: The Turkish Straits System (TSS), which regulates the transports of water, material and energy between
the Black Sea and the Mediterranean Sea has a two-layer flow with contrasting properties and a unique ‘maximal
exchange’ regime resulting from hydraulic controls. This sensitive system in the last century has been subjected to
increased environmental threats and literally has been abandoned for a silent death. The region surrounding İstanbul,
the only megapolis of Europe at present, currently is about to irreversibly lose the chance to live in peace with
nature. Within this context, the Canal İstanbul project is a candidate to pose one of the greatest risks for our seas.
Key Words: Straits, exchange flows, hydraulic control, turbulence, stratification, marine ecosystem.
1. INTRODUCTION
The Dardanelles (length 75 km, min. width 1.3 km) and Bosphorus (length 35 km, min. width 0.7 km)
Straits and the Marmara Sea (surface area 11,500 m2) make up the complex system of the Turkish Straits
connecting Mediterranean and Black Seas of extreme contrasts. The region is also encircled with some of
the widest continental shelves (max. depth 100m, width ~50 km) with adjacent deep basins (max. depth
1350 m in the Marmara Sea and 2350 m in the Black Sea).
The foundations of modern oceanography have been laid in İstanbul by Marsili [1], based on a series of
first-time measurements in the Bosphorus [2-4]. In addition to the density driven currents, a net through-
flow of about 350 km3/yr is maintained through the Bosphorus due to the differences in net water budget
of the adjacent basins. A two-layer exchange results, with the component due for the Mediterranean about
twice as large as the current flowing towards the Black Sea [5-12].
The rapid surface currents of the Bosphorus, forming recirculation cells near Beşiktaş north of the
Sarayburnu (Byzantion Pt.) headland, trapping fish in the Golden Horn facilitated active fishing, a major
source of income for the region since ancient times, quoted in Anaplous Bosporou by Byzantios, 5th
century AD [1, 13-15]. The ancient settlement of Troy, located at the mouth of the Dardanelles is the
other example of an ancient city thriving on fishing and trade, while living in peace with nature.
The hydrological regime, circulation, ecosystem and tectonics, all display extremes in the region. The
paleo transformations of the system between fresh water lake and sea basin are well known [16], with
projected impacts on human societies [17-19]. Climatic changes with rather short cycles of about 150-300
year periods are recorded in the bottom sediments of the Black Sea [20]. Large-scale climate patterns
such as the NAO, NCP and Indian Monsoons have great regional importance [21-22], with impacts on

ecosystems [23]. Yet it is not known what kind of risks are posed on the region by the present trend of
global warming, combined with extreme weather, floods, earthquakes, especially as İstanbul, already a
monster of a city, heads for further expansion, determined to destroy its remaining vital resources.
Figure 1. Chlorophyll concentration on the course of R/V BİLİM during April 2008.
Significant changes have occurred in the last century in the ecological status of the TSS, and mainly after
the industrialization and population expansion starting with the 1960’s. The eutrophic Marmara Sea
waters fed by Black Sea nutrients [24], as well as the efficient jet induced local recycling makes this
small basin a region of high productivity often far exceeding the Black Sea (Fig.1), with increasing
occurrences of mucus and toxic algae (Fig. 2). The plans for what is often inappropriately called as
‘development’ pose increasing risks of ecosystem crises and failures in the TSS, with implied effects on
adjacent basins, as many signs of deterioration are already easily discernible.
Figure 2. (a) Possible toxic plankton bloom near Tekirdağ; Milliyet, 24 April 2013 (b) from a jet flight
over the Marmara Sea on 28 April 2013 (Photo: Dr. Bettina Fach, IMS-METU), (c) MODIS ocean colour
image on 25 April 2013, showing the Bosphorus jet (dark colour) surrounded by what looks like coccolith
(green) and toxic plankton (orange) blooms.
2. MATERIAL AND METHODS
This short review is based on about 30 years of experience on oceanographic field experiments, as well as
the last 10 years of modeling development to understand and predict the complex physical behavior of the
TSS. Modeling the exchange flows in the TSS has been a grand challenge because of the need for fine
resolution and the ability to represent complex processes of stratified, turbulent, nonlinear flows through
the complex geometry of the region. The challenge has been taken by a number of steps, using models of

increasing complexity. A detailed modeling study of the Bosphorus Strait [25] based on ROMS have
revealed its basic hydrodynamics using both a hypothetical model domain of idealized geometry and a
realistic one with the high-resolution representation of the strait geometry. A model based on MITgcm
with identical geometry [26] has been shown to produce almost identical results, also in harmony with
measurements. A curvilinear grid MITgcm with extended features covering the entire TSS and fully
resolving the narrow Bosphorus [27-28] has further verified the results. A FEOM unstructured grid model
of the entire TSS is under development, as well as an isopycnal coordinates model used for climatological
predictions [29]. The detailed description of all the model development and parameters documented in
[25] is beyond the present scope and will also be presented in forthcoming papers.
However a particular application to expose the simplest coupled behavior of Canal İstanbul [25] is in
order here. This case was constructed with a simple straight canal of 25 m depth and 150 m width,
aligned parallel to the Bosphorus and subjected to the same boundary and initial conditions.
3. RESULTS
Although announced to be part of the grandiose scheme of ‘new İstanbul’, with satellite cities, airport and
peripheral highways and bridges, there is no official announcement of any intent to pursue environmental
research using scientific methods, let alone any release of information on the purpose, route and design
parameters of the Canal, including the socio-economic basis used in planning, which would normally be
required. Despite all the uncertainty surrounding Canal İstanbul, we have taken the liberty to investigate
the simplest questions on the possible effects on exchange, using an extension of the ROMS model of the
Bosphorus, by implementing a straight channel in parallel to the original one, with approximate
dimensions based on press accounts in the absence of incentive on the part of the establishment.
Figure 3. Model configurations and bathymetry for (a) Bosphorus Strait,
(b) Bosphorus plus Canal İstanbul (Sözer 2013).
The calculated model steady state response for a given net flux of 5600 m3/s is shown in Fig. 4 for the two
cases indicated in Figure 3. The Bosphorus exchange currents are shown in Fig. 4a for both cases
(uncoupled case shown with colours, coupled case with contours), with almost identical features, proving
that only a small change occurs in the Bosphorus, which is the dominant member of the coupled system.
The currents predicted in the simple Canal İstanbul case are shown in Fig. 4b, while Fig. 4c shows and
sea level variations in Canal İstanbul, as well as that along the Bosphorus Strait for both the uncoupled
and the coupled cases.

Figure 4. Model predicted currents in (a) the Bosphorus Strait (Bosphorus alone – colour palette, coupled
with Canal İstanbul – contours), (b) the idealized configuration of Canal İstanbul. (c) the surface
elevation along Canal İstanbul (green) and Bosphorus (red uncoupled, black coupled case).
We have thus created only a preliminary experiment providing the first impression on the effects of the
‘would be’ Canal İstanbul with a very simple model, but without disregarding the important coupling
effects between the two channels. The case is a good example of weak coupling, as the dominant member
continues to function without much change, while the new and weaker member is free to function in its
own way, yet only constrained by the dominant member.
We will not interpret the complex behavior of the Bosphorus, as that has been explained in [25]. As
regards the new channel of Canal İstanbul, the behavior is rather surprising, yet very simple. The two-
layer system, constrained by the Bosphorus has most of the flow in the upper layer, with a thin, supressed
lower layer for the given net flow. The upper layer is almost uniform throughout, except near the southern
end where high velocities occur, and the interface jumps to the surface. The sea level, in accordance with
this behavior, has the greatest sudden change near the southern end. These features point to critical design
issues, although the coupled time dependent behavior would be expected to be very different, possibly
with more violent oscillations in the Canal compared to Bosphorus having a maximal exchange regime.
Yet the most significant effect of Canal İstanbul seems to be an increase in total transport, with an
addition of its flux, found to be about ∼4% of the flux through the Bosphorus. Although this additional
flux appears too small compared to the Bosphorus, it amounts to 600-800 m 3/s for the studied cases.
Although much smaller than the typical range of fluxes through the Bosphorus (Fig. 5), this increase in
flux is comparable to medium sized rivers in the Black Sea, and in fact amounts to 3-4 times the
discharge of the important Sakarya river on the Turkish coast, and of the same order of magnitude as the

present discharge of the Nile river in the Mediterranean Sea. Furthermore, this increase is all too
significant because it will be carrying nutrient-loaded, polluted Black Sea water to the Marmara Sea
providing fuel to the furnace to hasten the ecological disaster there.
Figure 5. Upper-layer (Q1) and lower-layer (Q2) volume fluxes through the Boshorus as a function of the
net flux (Q=Q1-Q2), based on observational data and compared with the results from the Bosphorus model
(ROMS) of Sözer (2013) and the TSS model (MITgcm) of Sannino et al. (2014a,b) [25-28].
CONCLUSIONS
We wish that the current results derived from the most basic considerations lead decision makers to re-
consider the purpose and design of their mega-projects and create motivation for careful, much more
detailed and scientifically based studies before taking such great risks that can lead to ecological failures
of great economical impacts on a regional level.
ACKNOWLEDGEMENTS
The glimpse into the state and inner workings of the TSS presented here owes greatly to the life-time
efforts of researchers and technical personnel of the IMS-METU, the captains and crew of the R/V
BİLİM, as well as the many projects performed under the sponsorship of İSKİ of the Municipality of
İstanbul, TÜBİTAK, IAEA, EU, Italian Foreign Ministry and German Helmholtz Foundation.
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