Page "Black Sea" Paragraph 6

In the past, the water level has varied significantly.

Due to these variations in the water level in the basin the surrounding shelf and associated aprons have sometimes been land.

At certain critical water levels it is possible for connections with surrounding water bodies to become established.

It is through the most active of these connective routes, the Turkish Straits, that the Black Sea joins the world ocean.

When this hydrological link is not present, the Black Sea is a lake, operating independent of the global ocean system.

Currently the Black Sea water level is relatively high, thus water is being exchanged with the Mediterranean.

The Turkish Straits connect the Black and Aegean Seas and comprise the Bosphorus, the Sea of Marmara and the Dardanelles.