High in the sky and dotted across the oceans, two of the world's smallest yet most influential substances – aerosols and phytoplankton – stubbornly guard their secrets. Today, NASA launched the Plankton, Aerosols, Clouds, and Ocean Ecosystems Mission (PACE) to uncover that mystery. The mission's findings could hold the key to understanding how dramatically the world is changing as the world warms.
Aerosols are tiny dust particles, wildfire smoke, and fossil fuel pollution suspended in the atmosphere that absorb and reflect solar energy and promote cloud formation. This is a very complex dynamic that climate models still struggle to explain. Phytoplankton are microscopic plant-like marine organisms that form the basis of food webs. It also sequesters carbon and prevents the Earth's climate from warming further. “Phytoplankton are essentially moving carbon, but we need to understand how that changes over time,” says Jeremy Weldel of NASA's Goddard Space Flight Center.
PACE is a satellite observatory that provides scientists with an unprecedented view of these super important sky and sea inhabitants and helps predict how the world will evolve. “There is a cost to atmospheric warming and ocean warming, and the cost from a biological perspective is that it clearly changes the base of the food chain,” said Wardell, project scientist at PACE. says Mr.
Phytoplankton are very small but bloom in huge numbers, creating large green stripes across the ocean. It was certainly easy enough to monitor with satellites, but what we've seen so far is a more or less uniform green streak. But PACE is equipped with extremely sensitive instruments that can see the entire electromagnetic spectrum from the ultraviolet to the near-infrared in high resolution. (The visible spectrum that we can see is halfway between these two spectra.) As a result, PACE will be able to see all kinds of different greens.
Think about what you see when you stare into the forest. “The leaves of different trees are all green, but they're very subtly different greens, which means they're different plants,” Wardell says. “What we're really looking for is this very subtle color change.”
This will allow scientists to understand not only where and why phytoplankton occurs, but also what kind of communities they form. There are thousands of species of phytoplankton, some act as food for small animals known as zooplankton, some are more toxic, and some sequester more carbon than others. What modern satellites can see from space is like drawing a picture with a box of eight crayons, but to PACE's eyes, the seeds will look different. “What you get with PACE is a box of 128,” Werdell says.
Because the ocean is changing rapidly, it is important to better understand these phytoplankton communities. They absorb about 90 percent of the excess heat humans add to the atmosphere, especially over the past year as sea surface temperatures have risen to record highs and stayed there. While high temperatures themselves can be detrimental to the growth of some phytoplankton species, they may actually benefit other species that thrive as mercury rises.
More subtly, the warm water acts as a kind of cap on the ocean surface, with cold water swirling underneath. “My favorite Irish drink is like drinking half a glass of Guinness over a harp in a pub,” Wardell says. “This creates a barrier across vast expanses of the upper ocean, preventing nutrients in the colder water below the warmer layer from penetrating.”
Phytoplankton require these nutrients to grow, so continued warm water caps in certain regions will further disrupt communities of photosynthetic species. If zooplankton require fewer species for food, their numbers may also decline. Larger predators, such as fish, that feed on that zooplankton will then have an impact up the food chain. It could ultimately impact the food species humans rely on for protein.