December 7, 2020 - Ice on the Caspian Sea

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   Ice on the Caspian Sea
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   Sitting at the crossroads of Europe and Asia, the Caspian Sea claims
   the title of the Earth’s largest land-locked inland water body. It
   covers roughly 143,200 square miles (371,00 sq km) and borders five
   countries. Russia sits along the northwestern shore, and then, moving
   clockwise, comes Kazakhstan, Turkmenistan, Iran, and Azerbaijan.

   Although it is often called a lake and receives fresh water from
   roughly 130 rivers, including the mighty Volga, the waters of the
   Caspian Sea are saline. While the over-all saltiness is about one-third
   as much as the ocean, the salinity is not uniform. In the north, where
   the rivers enter, the water is freshest, and the southern waters are
   saltiest. The depth of the lake changes dramatically between north and
   south as well. Most of the north area sits over a shelf, leaving a
   depth of only 10 meters (30 feet) or less. Depth drops to hundreds of
   meters in the south, reaching as much as 1,000 meters (3,000 feet) in
   some areas.

   As winter comes to the Caspian Sea, frigid temperatures embrace the
   northern regions first—and often hardest—bringing frost to the land and
   encouraging ice formation. But more than air temperature affects
   freeze-up of the Caspian Sea. Salinity and depth also are important
   factors. Fresh water freezes at 32˚F (0˚C), but when salt is added, the
   freezing point drops. For every five parts per thousand salt content
   (salinity), the freezing point drops by 0.5 ˚F (0.28 ˚C). Also,
   shallower water cools more readily throughout the water column than
   deeper water, and the rapid cooling of the water column facilitates
   freezing. These factors explain why the northern Caspian Sea reliably
   freezes in the wintertime, while the southern section usually remains
   ice-free.

   The Moderate Resolution Imaging Spectroradiometer (MODIS) on board
   NASA’s Aqua satellite acquired a true-color image of the Caspian Sea on
   December 3, 2020. Bright white fast ice clings to the shore of
   Kazakhstan while open water can be seen near the Volga River Delta and
   southward. Tan sediment pours into the Caspian Sea from the Volga River
   and changes color to green as it sinks into the blue waters of the Sea.

   Image Facts
   Satellite:  Aqua
   Date Acquired: 12/3/2020
   Resolutions:  1km (64.4 KB),  500m (236.9 KB),  250m (731.4
   KB)
   Bands Used: 1,4,3
   Image Credit: MODIS Land Rapid Response Team, NASA GSFC



https://modis.gsfc.nasa.gov/gallery/individual.php?db_date=2020-12-07
 
