High in the sky and scattered across the seas, two of the smallest but most influential things in the world have stubbornly kept their secrets: aerosols and phytoplankton. Today NASA launched its Plankton, Aerosol, Cloud, Ocean Ecosystem mission, or PACE, to unravel its mysteries. The mission’s findings could be key to understanding how drastically the world is changing as it warms.
Aerosols are small pieces of dust, forest fire smokeand pollution from fossil fuels floating in the atmosphere, which absorb and reflect the sun’s energy and help form clouds, a tremendously complex dynamic that climate models still struggling to account for. And phytoplankton are the microscopic plant-like marine organisms that form the base of the food web. They also sequester carbon, prevent the Earth’s climate from warming further. “Phytoplankton basically move carbon around and we need to understand how that changes over time,” says Jeremy Werdell of NASA’s Goddard Space Flight Center.
PACE is a satellite observatory that will give scientists unprecedented views of these ultra-important inhabitants of the skies and seas, to help them try to predict how our world will evolve. “Warming of the atmosphere and oceans has a cost, and that cost, from a biological point of view, is that the base of the food chain will unequivocally change,” says Werdell, the PACE project scientist.
Although phytoplankton is tiny, it blooms in such quantities that it leaves large green swathes in the oceans. That’s been easy enough to monitor by satellite, sure, but so far what’s been observed has been more or less a uniform green streak. But PACE is equipped with an extremely sensitive instrument that can see in high resolution the entire electromagnetic spectrum, from ultraviolet to near-infrared. (The visible spectrum, which we can see, is between the two.) The effect is that PACE can see all kinds of different greens.
Think about what you see looking into a forest. “All the leaves on the different trees are green, but they have very subtly different greens, which means they are different plants,” Werdell says. “Really what we’re looking for are these very, very subtle color changes.”
That will allow scientists to determine not only where phytoplankton is blooming and why, but also what type of community it creates. There are thousands and thousands of species of phytoplankton: some act as food for tiny animals known as zooplankton, others are highly toxic, and some sequester carbon better than others. What modern satellites can see from space is like drawing with a box of eight crayons, but the species will look different to PACE’s eyes. “What we get with PACE is a box of 128,” Werdell says.
It is essential to better understand these phytoplankton communities due to the rapidity with which the oceans are transforming. They have absorbed something like 90 percent of the excess heat that humanity has added to the atmosphere, and over the last year in particular, sea surface temperatures. have soared to record levels and He was there. High temperatures themselves could negatively affect the growth of some phytoplankton species, but they could actually benefit others that thrive as the mercury rises.
More subtly, the warm water acts as a kind of layer on the ocean’s surface, with cooler waters swirling beneath. “It’s like drinking a half and half in your favorite Irish pub: Guinness floating on top of Harp,” Werdell says. “That creates a barrier in this huge expanse of land at the top of the ocean, where nutrients from the cold water beneath this layer of warm water cannot penetrate.”
Phytoplankton need those nutrients to grow, so if the warm water layer persists in a given area, that will further shake up the community of photosynthesizing species. If there are fewer species than zooplankton need to feed on, their numbers may also decrease. And then larger predators, like fish that eat zooplankton, will be affected up the food chain. That could eventually affect the food species that humans depend on for protein.