A transient but important part of Earth’s cryosphere is lake ice. The process of ice formation is important to protecting the health of lakes. As the upper layer of water is cooled by cold air temperatures, it becomes more dense than the water below it and sinks to the bottom of the lake, pushing warmer, less dense water to the surface. The turnover process happens a number of times until the surface water is cool enough to freeze to ice. This layer of ice then insulates the lake, keeping the lower water warm enough to remain liquid. The lake ice and snow on its surface block a lot of sunlight, which slowly kills aquatic plants, lowering the lake’s oxygen levels over winter. If the lake stays frozen for too long, oxygen levels can become dangerously low for fish and other aquatic life. In the opposite sense, if an ice season is short and a lake warms earlier than usual in spring, it can alter the ecological balance of the water and lead to serious problems, such as harmful algal blooms. For this reason, when lake ice forms and melts and other related details are considered important indicators of climate change.

Scientists and decision-makers interested in the study of lake ice alone and as it relates to climate change can find a host of valuable data available from NASA.