In 2002, NASA launched the Aqua Earth observing satellite. The spacecraft is part of a program to monitor of Earth’s environment from vantage points orbiting the planet. The satellite circles Earth every ninety-nine minutes in an orbit that travels from pole to pole. As the Earth rotates beneath it, a satellite in this orbit can survey most of the planet’s surface while maintaining a fixed relationship to incoming sunlight. The spacecraft carries six scientific instruments designed to monitor water in Earth’s atmosphere, and bodies of water on Earth’s surface.
In 2023 a team of researchers based in the United States and Great Britain published their analysis of one set of results from the satellite. The researchers studied data from a spectroradiometer that monitored light wavelengths reflected by the surface of the ocean. They found that, over the twenty years that the satellite has been on the job, about 56% of the ocean’s surface has changed in color. An expanse larger than Earth’s entire land surface has become slightly greener.
A greener ocean implies a change to microorganisms found in the surface layers of the ocean, called phytoplankton. Like plants, phytoplankton capture solar energy and synthesize energy-storing sugars. They directly or indirectly provide food for almost everything that lives in the ocean. Researchers don’t yet understand the consequences of the change. They believe that it results from global climate change, caused by human activities like burning fossil fuels. The finding confirms a consequence of global climate change predicted by theoretical models of the atmosphere. It is yet another piece of evidence confirming the reliability of these models and their predictions about our future.
