To a varying degree the Middle and Late Pleistocene ice sheets in nort
hern Eurasia redirected the drainage of major catchments in Europe and
western Siberia from the North Sea and Arctic Ocean south to the Casp
ian, Black Sea, and ultimately the Mediterranean. During the Late Weic
hselian, glacial meltwater reached the Mediterranean through the Dniep
r and Don catchments and to a minor extent through the Danube. During
the Warthe Substage of the Saalian, meltwater from the Volga was most
likely added. During the Drenthe Substage of the Saalian the watershed
shifted far to the east, and meltwater reached the Mediterranean also
from the Ob, Irtysh, Yenisei, and Tunguska catchments in Siberia. Dep
ending on the extent of the ice sheets, the increase in freshwater sup
ply during deglaciations resulted in reductions of Mediterranean overf
low into the North Atlantic. Such overflow reductions may have reduced
vapour transport to the ice sheets and thus accelerated wastage.