Tonga eruption sparked pressure spikes in Michigan, weather service says

When a massive undersea volcanic eruption wreaked havoc in the South Pacific last weekend, special equipment for the National Weather Service throughout Michigan reported disturbances in the atmosphere.

On Saturday, NWS sites across the state briefly registered the results of "shockwaves," small spikes in atmospheric pressure, said Alex Manion, a meteorologist with the station in White Lake Township.

"It was more pronounced on the west site of the state ... but we did see a little bit," he said.

Satellite images showed the spectacular eruption that took place Saturday evening local time, with a plume of ash, steam and gas rising like a mushroom cloud above the blue Pacific waters.

Tsunami waves of about 80 centimeters (2.7 feet) crashed into Tonga’s shoreline, and New Zealand Prime Minister Jacinda Ardern described damage to boats and shops on Tonga’s shoreline. The waves crossed the Pacific, drowning two people in Peru and causing minor damage from New Zealand to Santa Cruz, California.

A sonic boom could be heard as far away as Alaska and sent pressure shockwaves around the planet twice, altering atmospheric pressure that may have briefly helped clear out the fog in Seattle, according to the National Weather Service. Large waves were detected as far away as the Caribbean due to pressure changes generated by the eruption.

Meanwhile, the pressure fluctuations were small but immediate Saturday in the Midwest.

The National Weather Service said on Twitter that part of the shockwave reached the Chicago area between about 8:20 a.m. and 8:30 a.m. CST Saturday, "with a clear spike in pressure observed" at O'Hare International Airport.

It had also reached Rochester, Minnesota, and La Crosse, Wisconsin, around 8:15 a.m. NWS said on Facebook.

Just before 10 a.m. EST, altimeters recorded "a very slight increase in pressure at stations" across Michigan, Manion said.

At Coleman A. Young Municipal Airport in Detroit, the pressure climbed to 30.47 inches before falling to under 30.40 by 3 p.m., according to weather service data.

Flint notched similar readings, along with Gerald R. Ford International Airport in Grand Rapids, which peaked at 30.46, and Sawyer International Airport in Marquette, which reached 30.52, the weather service websites showed.

Gaylord's regional airport reached 30.50, while the local NWS station tweeted that its measurement sites in Traverse City, Sault Ste. Marie, Alpena and Roscommon County all saw jumps around the same time.

"The immense amount of pressure that was released had to emanate and go outward," Manion said, adding the pressure spikes were short-lived as the shock wave spread. "It looked to be really a few hours of buildup before slowing going back down."

Scientists said they didn’t think the eruption would have a significant impact on the Earth’s climate.

Huge volcanic eruptions can sometimes cause temporary global cooling as sulfur dioxide is pumped into the stratosphere. But in the case of the Tonga eruption, initial satellite measurements indicated the amount of sulfur dioxide released would only have a tiny effect of perhaps 0.01 Celsius (0.02 Fahrenheit) global average cooling, said Alan Robock, a professor at Rutgers University.