JACKSONVILLE, Fla. – It may come as a surprise to learn that in January 2022, a tsunami reached the entire East Coast of the United States, including Florida.
For many, “tsunami” conjures images of the Pacific—Japan, Indonesia, Alaska—not the tranquil stretches of the Atlantic seaboard.
But this wasn’t your average tsunami, nor was it a typical storm tide. This was a rare marine hazard from the convergence of a storm surge, a meteotsunami, and atmospheric waves triggered by a volcanic eruption over 7,000 miles away in the South Pacific.
The result was a 4.9-foot tsunami along the Atlantic City region. The Northeast Florida coast experienced a small 2- to 7-inch wave.
Volcanic shockwave, not an earthquake
To understand what made this event so unusual, it helps to compare it with a similar moment in history.
Back in 2004, a massive tectonic earthquake off the coast of Sumatra sent tsunami waves surging across the Indian Ocean—and eventually, across the Atlantic Ocean to reach the East Coast of the U.S.
That event was documented by researchers like Thomson et al. (2007), who identified it as the first seismically generated tsunami recorded along the Atlantic seaboard.
But the 2022 tsunami wasn’t caused by shifting tectonic plates.
Instead, it was born from the Hunga Tonga-Hunga Ha’apai volcanic eruption, which unleashed a staggering amount of energy into the atmosphere, not through the crust, but through the sky.
The explosion produced atmospheric pressure waves, known as Lamb waves, which circled the globe at the speed of sound.
Much like how squall lines or sea breezes can stir the water, this pressure wave from halfway around the planet did the same, but on a global scale.
When these pressure waves passed over oceans, including the Atlantic, they displaced the sea surface, triggering a type of tsunami that is atmospheric in origin.
In essence, this was not an oceanic tsunami traveling from the source but an “atmospheric tsunami” that hitched a ride on the air.
The Tonga tsunami waves recorded on the East Coast of the United States were produced by explosion-forced Lamb waves in the atmosphere.
These waves traveled at a speed of 693 mph and completed three circumventions of the globe, each time initiating sea level response along the U.S. East Coast.
Sensitive instruments worldwide detected sudden air pressure changes in the Lamb waves as they passed. These pressure shifts over oceans triggered meteotsunamis—tsunamis driven by atmospheric forces.
Like seismic tsunamis, they travel as long, low waves across deep water, growing shorter and taller in shallower areas, potentially leading to hazardous coastal surges.
How high did the water rise?
A report earlier this year revealed the tsunami signal was a subtle 2 to 7 inches in Northeast Florida, but as you moved northward, the impacts became more significant.
Along parts of New Jersey and Delaware, water levels peaked at over 4.6 feet above normal — amplified by a rare trifecta.
This stacking of water from three different atmospheric and oceanic processes created a localized flooding threat that defied conventional expectations:
- A storm surge of up to 3.9 feet
- A meteotsunami of 2.8 feet
- And a Tonga-induced tsunami wave of about 1 foot
The triple force setup
In addition to the atmospheric tsunami, two more distinct ocean-forcing mechanisms combined into one high-impact flood scenario for New Jersey and Delaware.
First came the storm surge, driven by a rapidly intensifying extratropical bomb cyclone that pushed ocean water ashore with strong winds and a plunging barometer.
Then, a meteotsunami—triggered by a fast-moving atmospheric disturbance riding the shallow continental shelf—amplified the sea surface through a resonance effect, like plucking a guitar string at just the right frequency.
This resonance—called Proudman resonance—amplified wave heights along the coast, particularly from North Carolina to New Jersey.
All this goes to show that the East Coast isn’t immune to far-field tsunami impacts—even from the other side of the planet. They also show that tsunamis don’t need an earthquake to be dangerous.