Sea spray is a phenomenon that forms where the ocean meets the atmosphere. It consists of tiny airborne droplets from the ocean. This dynamic process represents a continuous, often unseen, presence in coastal environments and beyond, influencing various natural systems.
What Sea Spray Is
Sea spray consists of microscopic droplets of seawater suspended in the air, acting as an atmospheric aerosol. These droplets are a complex mixture of dissolved inorganic salts, primarily sodium chloride. Other chemical ions commonly found in seawater, such as potassium, magnesium, calcium, and sulfate, are also present.
Beyond inorganic salts, sea spray also incorporates organic matter, including proteins, sugars, and even microorganisms like bacteria, viruses, and algae from the ocean. The size of these droplets varies widely, typically ranging from approximately 0.05 to 10 micrometers in diameter, with smaller droplets remaining airborne for longer durations. The specific composition and size distribution of sea spray particles can influence their atmospheric behavior, including their ability to absorb water.
How Sea Spray Forms
Sea spray forms primarily from bursting air bubbles at the ocean’s surface, a process initiated by breaking waves. Breaking waves entrain air, forming bubbles that rise and burst at the surface, ejecting water droplets into the atmosphere.
Two main types of droplets are produced during this bubble bursting process: film drops and jet drops. Film drops originate from the disintegration of the bubble’s thin film cap, often being smaller in size, typically less than 1 micrometer in radius.
Jet drops, in contrast, are formed when the bubble cavity collapses, sending a high-speed jet of water upwards that subsequently breaks into larger droplets, ranging from 2 to 500 micrometers in radius. Wind shear over wave crests also contributes to sea spray formation, particularly for larger droplets, by directly tearing water from the wave tops, especially at high wind speeds.
The Importance of Sea Spray
Sea spray influences Earth’s systems, including atmospheric processes, ecological dynamics, and coastal infrastructure. In the atmosphere, sea spray acts as cloud condensation nuclei (CCN), allowing water vapor to condense into cloud droplets. This affects cloud formation, properties like reflectivity and lifetime, and influences global weather patterns and the Earth’s radiation balance. It also contributes to atmospheric chemistry and particle transport.
Ecologically, sea spray carries marine nutrients, such as salts and trace elements, inland, impacting terrestrial ecosystems. For example, some studies suggest that these transported nutrients can affect plant growth and species distribution in coastal areas. Sea spray also serves as a mechanism for distributing marine microorganisms, including bacteria, viruses, and algae, into the atmosphere. These airborne microbes can travel significant distances, potentially influencing both marine and terrestrial life.
Sea spray also impacts coastal environments and human activities. The salts accelerate corrosion of metallic objects and building materials in coastal regions, due to atmospheric oxygen and moisture. This effect is pronounced near breaking waves and can extend inland, affecting infrastructure. It also affects air quality in coastal areas, containing various organic and inorganic compounds.