Abstract
Counterflowing waters of the Black Sea and Mediterranean Sea are mixed
by turbulent entrainment processes along their course through the
Turkish Straits. In the Bosphorus Strait, the entrainment into the
upper layer from below is abruptly increased when the flow is accelerated
in the narrower southern reach, where the flow passes through a contraction.
In contrast, the lower layer salinity decreases towards the north
first by gradual entrainment within the Strait and later at an increased
rate in the wide continental shelf region upon exit into the Black
Sea. After passing over the sill located north of the Strait, the
flow on the continental shelf proceeds in the form of a gravity current
following the local slopes. The topography of the shelf region, assembled
from various sources of high-resolution surveys and maps, is reminiscent
of a river delta. The water properties and thickness of the Mediterranean
plume is modified by turbulent entrainment, shelf currents, stratification,
bottom friction and slope. The flow first spreads out on the mid-shelf
slope, follows the delta features to reach the shelf edge and, finally,
cascades down the steep continental slope. Horizontal spreading by
convective instabilities and eastward propagation of anomalous properties
along the continental slope are characteristic features of the deeper
region adjacent to the shelf. The behaviour of the density current
is revealed by results obtained from a reduced gravity model, suggesting
that the slope and fine-scale features of the bottom topography are
crucial elements in determining plume behaviour. The model results
are found to be robust to environmental changes and in good correspondence
with observed flow features, especially when the topography with
realistic fine scales and slope are adequately represented. (C) 2001
Elsevier Science B.V. All rights reserved.
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