Modeling of the Turkish Strait System Using a High Resolution Unstructured Grid Ocean Circulation Model

Mehmet Ilicak,Nadia Pinardi,Emanuela Clementi,Giovanni Coppini,Stefania Angela Ciliberti,Ivan Federico,Ivano Barletta,Sabri Mutlu,Haldun Karan

doi:10.3390/jmse9070769

Abstract

The Turkish Strait System, which is the only connection between the Black Sea and the Mediterranean Sea, is a challenging region for ocean circulation models due to topographic constraints and water mass structure. We present a newly developed high resolution unstructured finite element grid model to simulate the Turkish Strait System using realistic atmospheric forcing and lateral open boundary conditions. We find that the jet flowing from the Bosphorus Strait into the Marmara creates an anticyclonic circulation. The eddy kinetic energy field is high around the jets exiting from the Bosphorus Strait, Dardanelles Strait, and also the leeward side of the islands in the Marmara Sea. The model successfully captures the two-layer structure of the Sea of Marmara. The volume transport at the Bosphorus is around 120 km3/year which is consistent with the recent observations. The largest bias in the model is at the interface depth due to the shallower mixed layer.

Highlights

We have presented a new high resolution unstructured grid model for the Turkish
The System of HydrodYnamic Finite Element Modules (SHYFEM)-Turkish Strait System (TSS) model was run for four years and successfully reproduced vertical water mass structure, horizontal circulation, and volume fluxes through the Bosphorus and Dardanelles Straits
Previous models observed similar circulation patterns [5,17,21]. Both mean and eddy kinetic energy fields are high around the jets

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Most ocean circulation models use structured grids with finite difference/volume discretizations These types of grids are challenging in modeling the TSS system because of the narrow and long Bosphorus and Dardanelles Straits, and the deep basins of the Marmara Sea. The complex topography and two-layer density structure require multiple hydraulic controls in both Straits [9]. Stanev et al used the SCHISM model for interconnected basins including the Black Sea, the TSS, and the northern Aegean Sea [20] They used realistic atmospheric forcing with lateral open boundaries in the south. The Finite Element Sea-Ice Ocean Model (FESOM), another unstructured grid model, was used by Aydogdu et al to study the circulation of the TSS [21] They analyzed the combined response of the Sea of Marmara with atmospheric forcing and strait dynamics.

Model Setup

Results

Mean Surface Circulation and Water Mass Structure

Water Mass Validation

Volume Fluxes through the Straits

Summary and Conclusions