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   September 15, 2022 - The Shrinking Coastline of the Caspian Sea   
      
      The Shrinking Coastline of the Caspian Sea   
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      Measured by surface area, the Caspian Sea is the Earth’s largest inland   
      water body, spanning about 143,200 square miles (371,000 square   
      kilometers). Measured by economic, social, and biodiversity standards,   
      it is priceless. The Caspian contains a rich oil and gas reserve, an   
      important fishery, resources for agriculture, provides for recreation   
      and work for large population living nearby, and contains many   
      important and sensitive species—for example, it contains an estimated   
      90 percent of the last sturgeon left in the world.   
      
      Every square inch of the Caspian Sea holds ecological treasure, but the   
      northern section holds a particularly important and sensitive   
      ecosystem. Here, the shallow waters teem with mollusks, crustaceans,   
      fish, and birds. Seals raise their pups on winter ice that usually only   
      forms in this part of the lake. All rely on a healthy water level for   
      their existence. However, the Caspian Sea is rapidly shrinking.   
      
      Radar altimetry data collected by multiple satellites and compiled by   
      NASA's Global Water Monitor indicate that the Caspian's water levels   
      have been dropping since the mid-1990s. As climate change causes   
      increased air temperature, evaporation will increase—and will be a   
      primary driver of loss of water from the Caspian Sea. In a paper   
      published in 2019, it was estimated that Caspian water levels could   
      drop by 9 to 18 meters (30 to 59 feet) by the end of the 21st century,   
      enough that it would lose about a quarter of its area and uncover about   
      93,000 square kilometers (36,000 square miles) of dry land. That is an   
      area about as large as Portugal.   
      
      In a newer paper, published in 2021, scientists ran several different   
      models to estimate water loss in the Caspian Sea due to climate change,   
      which gave estimates of loss by the year 2100 as low as 8 meters (36   
      ft) and as high as 30 meters (98 ft). Because extraction (human use or   
      diversion of water) is also an important driver of water loss in the   
      Caspian, the scientists also estimated this factor—something overlooked   
      in most other estimates. They found that water extraction would add up   
      to 7 meters (23 feet) further loss. While the deepest parts of the   
      Caspian plunge to more than 1,000 meters below sea level, the northern   
      portion has an average depth of only 5-6 meters. All but one of the   
      models in this study showed complete desiccation of the northern   
      section of the Caspian by the end of the 21st century.   
      
      On September 6, 2022, the Moderate Resolution Imaging Spectroradiometer   
      (MODIS) on the Terra satellite acquired a true-color image of the   
      northeastern section of the Caspian Sea. The sprawling, green Volga   
      River Delta can be seen along the northern coast at the left (west)   
      edge of the image. Swirls of green and tan color the shallow water,   
      created by the sediment carried in by the fresh water of the Volga and   
      by currents that stir up sediment from the shallow sea floor in this   
      region. A broad area of the coastlines near the waters are tinted light   
      gray. In addition, patches of bright white along with a large swath of   
      white color the landscape southeast of the Caspian. These light colors   
      are salt and other minerals left behind after evaporation.   
      
      For our Image of the Day, we have compared the September 6, 2022 image   
      with a true-color image acquired by the MODIS instrument on Terra on   
      September 20, 2006. In this image, there is no light-colored,   
      salt-laden halo along the northern shore and only a relatively small   
      “salt-shadow” in the east and south. Water fills the serpentine area   
      that, twelve years later, has become a thick mineral crust.   
      
      While this Image of the Day gives a striking comparison illustrating   
      the shrinking shoreline of the Caspian Sea, it is even easier to   
      visualize the change with a roll-over comparison. Thanks to the NASA   
      Worldview App, this can be easily visualized simply by clicking   
       here. Using the measurement tool in the lower left corner of the   
      roll-over comparison on Worldview, it appears that the eastern   
      coastline has receded approximately 17.5 feet (5.3 meters) in the last   
      twelve years.   
      
      Image Facts   
      Satellite:  Terra   
      Date Acquired: 9/11/2022   
      Resolutions:  1km (319.8 KB),  500m (788.6 KB),  250m (513.9   
      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=2022-09-15   
       
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