Paleo-evolution of the Black Sea watershed: sea level and water transport through the Bosporus Straits as an indicator of the Lateglacial–Holocene transition |
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Authors: | Goran Georgievski Emil V Stanev |
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Institution: | (1) Institute for Chemistry and Biology of the Marine Environment (ICBM), Department of Physical Oceanography (Theory), University of Oldenburg, Oldenburg, Germany |
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Abstract: | The paleo-evolution of the Black Sea level during the Lateglacial–Holocene transition is still unclear, which motivates us
to provide new estimates for that period based on the analysis of water budget. Hydrological conditions in the Black Sea catchment
area are reconstructed here using water balance equation, available data, and constraints based on simple theory relating
the runoff ratio with climatic characteristics. In order to estimate the impact of the aridity of climate we consider two
alternative scenarios: (1) climate change under constant in time gradient in precipitation and evaporation over land and sea,
and (2) climate change accounting for changes in the horizontal distribution of precipitation and evaporation. Hydrological
data are compiled from available present-day data and paleo-observations. A number of sensitivity experiments is carried out
revealing that the hydrological conditions in the Black Sea watershed should have evolved towards a very arid climate (similar
to the present-day climate in the Caspian Sea area) in order to initiate a drop of sea level of ∼100 m below the sill depth
of the Bosporus Straits, as speculated in some recent research. Estimates of sea level changes reveal a qualitative agreement
with the coast-line evolution inferred from paleo-observations. The Younger Dryas draw down of the Black Sea starts at about
13.3 to 13 kyr BP, with a maximum low-stand of 104 m at 11.5 kyr BP. In an arid climate scenario the sea level reaches the
outlet at about 8.8 to 7.4 kyr BP. Approximately at that time, Mediterranean sea level was about 10 m higher, making flooding
events of the Black Sea possible. However, the nature and exact timing of the Holocene reconnection depends also on other
(not well known) factors; one of them is the Bosporus sill depth, motivating further research in this field. Estimates of
the water transport through the Bosporus Straits are also provided for the time of Lateglacial–Holocene transition. |
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