When Lightning Touches Water
Why is it necessary to get out of the ocean during a storm? A lifeguard tells everyone to get out of the water immediately, but it shouldn’t matter because everyone is already wet. The answer is lightning.
A flash of lightning, which has about 300 million volts and 30,000 amps, is deadly to humans (BBC News, 2014). Lightning occurs during storms when there is enough wind to cause charges inside clouds to separate. Electrons in the cloud peel off water particles, leaving the water particles positively charged and joining other particles to make them more negatively charged. Positive charges start to gather near the top of the cloud while negative charges gather near the bottom (Cappucci, 2022). The separation of these charges creates both an electric field between the negative and positive charges in the cloud, and between the negative charges in the cloud and the positive charges on the ground. The positive charges on the ground attract the negative charges at the bottom of a cloud, and they start to move toward each other. Once the charges from the ground and the cloud meet, the negative charges start to flow downward and an electric current is shot up to the cloud along the path that the negative charges came from (How Lightning, n.d.) For this to happen, the air has to reach 3 million volts per meter. At this point, the charge is no longer contained and creates a path downward as it continues to heat up the air around it. The charge moves in what is called a “stepped ladder” formation, a direct, fractal shaped path (Cappucci, 2022). The current is what we see as lightning. Because it happens so fast, it looks like the lightning is coming from the cloud, but it is actually coming from the ground. This type of lightning is most dangerous, but another type of lighting, that which occurs between the negative and positive charges within a cloud, happens much more often. Fascinatingly, lightning can also occur in circumstances beyond storms. Other environments, like dust storms, forest fires, or volcanoes can cause a similar motion between charged particles, leading to lightning strikes. (How Lightning, n.d.).
The physics of lightning is already complicated, but its interaction with water adds another layer of complexity. Lightning hitting the sea is rare as most lightning strikes are on land. This is because over the ocean the air contains sea salt, which attracts charges but turns the charges into heavy droplets of water before they can come down as electric charges (Balthazaar, 2023). Using satellite technology, scientists have observed the patterns of lightning when interacting with oceans. They concluded that lightning flashes over the ocean are stronger, longer, and brighter than those over land. The experiments found that the greater the concentration of salt, the brighter the lightning. Lightning strikes on water are only about 10% of all strikes worldwide ("Why Is Lightning," 2020). However, once it does strike water, it spreads out because salt water is a good conductor of electricity. Because of this, objects in the ocean like fish or boats can get electrocuted (Ocean Today, 2011). A study in the Journal of Atmospheric and Solar-Terrestrial Physics found that the intensity of lightning over the ocean is directly correlated to the concentration of salt in the water. In other words, when salinity increases, because salt is a better conductor, lightning strikes are brighter and more intense.
Lightning is as interesting as it is dangerous. Despite being more likely to strike land, lightning striking water can be more risky out at sea. While electric fields and currents are not discussed day-to-day, understanding the impact of lightning on water and how it works can help to save people’s lives. Luckily, lightning fatalities are decreasing because of increased awareness and better weather-predictability. Nevertheless, it is important to be aware of how lightning behaves in order to stay safe.
References
Balthazaar, D. (2023, January 16). Lightning at Sea? Science World Scholastic. Retrieved December 19, 2024, from https://scienceworld.scholastic.com/issues/2022-23/011623/lightning-at-sea.html?language=english
Cappucci, M. (2022, August 5). What happens when lightning strikes -- and how to stay safe. The Washington Post. Retrieved December 23, 2024, from https://www.washingtonpost.com/climate-environment/2022/08/05/lightning-thunder-thunderstorm-facts-safety/
How lightning works. (n.d.). Canada.ca. Retrieved December 19, 2024, from https://www.canada.ca/en/environment-climate-change/services/lightning/science/how-lightning-works.html
When Lightning Strikes [Video]. (2011, July 5). Ocean Today. https://oceantoday.noaa.gov/lightning/
Who, what, why: What happens when lightning hits sea? (2014, July 28). BBC News. Retrieved December 23, 2024, from https://www.bbc.com/news/blogs-magazine-monitor-28521789
Why is lightning more intense over the oceans? (2020, March 31). Journal of Atmospheric and Solar-Terrestrial Physics. Retrieved December 23, 2024, from https://www.sciencedirect.com/science/article/abs/pii/S1364682620300766
