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Sea spray off the Washington coast. Public domain.
If you stand near the water’s edge on a breezy day, when the waves are breaking on shore, you can feel the sea spray — a mixture of water, salt, and microscopic organisms. While much of the spray falls back to the surface, some of it is swept high into the sky. There, it can help form clouds — playing a role in the weather, and in the long-term climate.
Clouds play a double role in regulating the climate. They reflect sunlight into space, which keeps the surface cooler. But they also prevent heat from Earth itself from escaping into space, keeping the surface warmer. The balance depends on the amount of cloud cover and the composition of the clouds.
And that depends on the “seeds” from which a cloud’s water droplets grow — tiny grains of dust, pollen, soot, or other materials. That includes particles from the ocean.
As waves collapse, they churn up a fine mixture of water droplets and bubbles. The bubbles are made of salt, but they can contain bacteria, viruses, and tiny organisms known as phytoplankton. As it climbs into the sky, a particle of salt or organic matter can form the nucleus of a water droplet.
Research suggests that the organic material plays a larger role in cloud formation than previously thought. And there’s evidence that high levels of bacteria can reduce sea spray’s ability to help make clouds.
There’s also concern that the changing climate could alter the variety of phytoplankton found at the ocean surface — perhaps changing the way clouds form over the oceans.
