Caspian Sea
The Caspian Sea, like the Black Sea, Namak Lake, and Lake Urmia, is a remnant of the ancient Paratethys Sea. It became landlocked about 5.5 million years ago due to tectonic uplift and a fall in sea level. During warm and dry climatic periods, the landlocked sea almost dried up, depositing evaporitic sediments like halite that were covered by wind-blown deposits and were sealed off as an evaporite sink when cool, wet climates refilled the basin. (Comparable evaporite beds underlie the Mediterranean.) Due to the current inflow of fresh water, the Caspian Sea is a freshwater lake in its northern portions, and is most saline on the Iranian shore, where the catchment basin contributes little flow. Currently, the mean salinity of the Caspian is one third that of Earth's oceans. The Garabogazköl embayment, which dried up when water flow from the main body of the Caspian was blocked in the 1980s but has since been restored, routinely exceeds oceanic salinity by a factor of 10.
Laptev Sea
The sea is characterized by the low water temperatures, which ranges from in the north to in the south-eastern parts. The medium water layer is warmer, up to 1.5 °С because it is fed by the warm Atlantic waters. It takes them 2.5–3 years to reach the Laptev Sea from their formation near Spitsbergen. The deeper layer is colder at about −0.8 °С. In summer, the surface layer in the ice-free zones warms up by the sun up to 8–10 °С in the bays and 2–3 °С in the open sea, and remains close to 0 °С under ice. The water salinity is significantly affected by the thawing of ice and river runoff. The latter amounts to about 730 km and would form a 135 cm freshwater layer over the entire sea; it is the second largest in the world after the Kara Sea. The salinity values vary in winter from 20–25‰ (parts per thousand) in the south-east to 34‰ in the northern parts of the sea; it decreases in summer to 5–10‰ and 30–32‰ respectively.