English: January 25, 2024 January 1, 2024

The Caspian Sea is the largest brackish-water lake on Earth, spanning about 143,200 square miles (371,000 square kilometers)—an area only slightly smaller than the U.S. state of Montana. It is also a sea of contrasts, with a shallow and slightly saline north end and a dramatically deep and much saltier southern end. These differences make big differences, especially when it comes to the formation of wintertime ice. The Northern Caspian Sea freezes over most winters, although the thickness, area covered, and even the ridges in the ice dependent on variable factors such as surrounding air temperature, winds, and fluctuating water depth. The Middle Caspian sees ice along the coastlines only in severe winters, while the Southern Caspian does not ice up.

Freeze-up on the Northern Caspian can start as early as November, but warm temperatures in 2023 delayed ice formation. A severe cold blast in early December brought enough of a chill to create a thin layer of ice over much of the water by mid-December, but it wasn’t until January 2024 that winter really got underway in Kazakhstan and the portion of Russia bordering the Northern Caspian Sea. As temperatures plummeted, the Northern Caspian rapidly froze over.

The Moderate Resolution Spectroradiometer (MODIS) on NASA’s Aqua satellite acquired a true-color image of snow and ice over the Northern Caspian Sea on January 24, 2024. Despite the thoroughly frozen condition of the north, no ice covers the visible portion of the Middle Caspian Sea, where the water looks bright blue. Snow also covers the surrounding lands of Kazakhstan (north and east) and Russia (west).

A second Aqua MODIS true-color image was acquired of the same region on January 1, 2024, and it can be viewed by clicking on the date below the images. On that date, ice covered only a small portion of the northernmost Caspian Sea. In addition, tan sediment swirled in the shallow waters. Toggling back and forth between the images will show what a large difference a few weeks can make in the life of the Caspian Sea.