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  • Author or Editor: Ümit Ünlüata x
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Ümit Ünlüata

Abstract

The presence of low-frequency motions in the Cilician Basin (the northeastern Mediterranean Sea) is investigated. An f-plane, barotropic, wind-driven model is utilized by taking advantage of the channel-like geometry of the basin. An asymptotic method (Allen, 1976) is employed to decouple the channel proper from its narrow and steep coastal margins. A resonant response is predicted at the cut-off frequencies for which the group velocities vanish. Both this resonant response and another form of resonance are discussed. Partial support is found from available data.

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Emin Özsoy
,
Ümit Ünlüata
, and
Mustafa Aral

Abstract

Numerical modeling techniques are used to study tsunami propagation in the eastern Mediterranean. In addition to the propagation patterns, the amplification due to the geometries of the continental shelf and the basin are studied in detail. The surface displacement at selected strategic locations is frequency-analyzed to obtain the resonances and their modal shapes. Coupled resonances are identified in the Cilician Basin-Gulf of Iskenderun system.

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Ümit Ünlüata
,
Temel Oguz
, and
Emin Özsoy

Abstract

Along the southern Turkish continental shelf, the intensity of the observed mean flow has a considerable degree of variability. The relatively strong currents along the straight portion of the coast is reduced significantly in the nearshore region upon encountering irregularities in the form of bays and headlands. As a possible explanation of such blockage by coastal irregularities, a linear, homogeneous wind-stress free model is presented incorporating the constraints of topographic steering and linear bottom friction. Solutions are given for an idealized case of an abrupt indentation on a straight coast adjoining a linearly deepening shelf. The directions preference of blocking and the applicability of boundary layer approximations am discussed. Numerical solutions are obtained for the realistic bathymetry and coastal configuration along the southern Turkish continental shelf. The concepts developed are applied to the observed blocking features.

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Temel Oguz
,
Emin Özsoy
,
Mohammed A. Latif
,
Halil I. Sur
, and
Ümit Ünlüata

Abstract

Recent hydrographic observations obtained in the Bosphorus Strait illustrate several features of the flow that may be related with the internal hydraulics. A two-layer numerical model indicates that the two-way exchange flow may indeed be subject to a series of internal hydraulic adjustments along the strait due to morphological features such as sills, a contraction and abrupt expansion of the width of the strait. The model identifies three distinct regions of the supercritical flow. The lower-layer flow of the Marmara Sea origin is directed to the north towards the Black Sea in a progressively thinning layer and is controlled by the sill located near the Black Sea entrance of the strait. The upper-layer water of the Black Sea origin flows in the opposite direction and is controlled upon reaching the constricted region located about 10–12 km away from the Marmara end of the strait. The upper-layer flow is then matched to the subsequent subcritical conditions by undergoing an internal hydraulic jump and becomes subject to another critical transition near the abruptly widening exit section into the Marmara Sea. The controls exerted by the northern sil and the contraction are connected by a subcritical region whereas the supercritical conditions downstream of these controls isolate the two way exchange from the conditions in the adjacent regions. In this way, the requirement for the maximal exchange is met implying that the Bosphorus Strait achieves the maximum possible transports in the layers depending on the magnitude of net barotropic transport.

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