Hunga Tonga volcanic eruption was largest in 3 decades

ANCHORAGE, Alaska (KTUU) - The Hunga Tonga ha’apai volcanic eruption that occurred Friday evening sent pressure waves around the world, multiple times. The Hunga Tonga undersea volcanic eruption was the largest on earth over the last 30 years, according to Research Physical Scientist Brian Brettschneider with the National Weather Service Alaska region.

Brettschneider said that the ash created by the eruption will likely cause a slight cooling effect on the climate, though not as dramatic as short-term climate changes from past volcanic eruptions. In 1815, the climate impacts caused by the Mount Tambora volcanic eruption caused what was called “the year without a summer.”

“What we’re seeing so far is a fairly minor amount of climate altering stratospheric sulfur particles have been detected so far,” Brettschneider said. “A pretty small amount relative to the size of the eruption, so kind of our first initial best guess is that there is going to be a pretty minor climate impact over the next few years.”

In an interview with Alaska’s News Source, Brettschneider compared the eruption to past volcanic events, and said that the pressure wave that disbursed from the eruption was unique among volcanic events. He said that the tsunami advisories and waves sent around the world were caused by the pressure wave, not seismic events or water displaced from portions of a volcano falling into the ocean, as has been the case with Mount Augustine in the past.

“This one is really caused by the pressure wave itself which is again really unprecedented at this scale. So that generated the initial tsunami, but even here in Alaska, some of the tsunami surges were as high as one meter and really an indication that it was caused by the pressure is if you look over in Puerto Rico, they actually had a little bit of a tsunami surge of about, I believe about 10 centimeters and there’s land — unbroken land — between the volcano and where Puerto Rico is, so it couldn’t have propagated across the water but it had to have been the pressure wave itself moving through,” Brettschneider said.

Not only did the pressure wave arrive in Alaska at around 3:30 a.m. on Saturday, but a second wave was felt around 11 p.m. that night. For context, Brettschneider compared that to the 1883 Krakatoa eruption which caused a pressure wave that made three and a half trips around the globe and was felt seven times. Brettschneider said that the Hunga Tonga eruption was equivalent to 2% of the pressure released in the Krakatoa eruption.

The climate impacts caused by volcanic eruptions occur because the majority of the solar energy received by the earth occurs in tropical regions.

“When you have an eruption in the tropics that potentially will put a lot of ash and sulfur particles in the stratosphere and block sunlight that has the potential to affect the climate of the entire globe — especially again in the tropics — that’s where most of our planet’s solar energy comes from,” Brettschneider said.

Brettschneider said that the rise in sea level pressure during the 19.3 hours in between pressure waves arriving in Anchorage was unrelated to the volcanic eruption, and that the majority of the ash created by the eruption would fall in the open water of the Pacific Ocean or on south Pacific Islands. The Hunga Tonga eruption was the largest volcanic event since the Mount Pinatubo blast in 1991 in the Phillipines

“The Novarupta eruption in Alaska in 1912 was even larger than Mount Pinatubo, but because it occurred at such a high latitude where a relatively small fraction of the earth’s total solar energy arrives, anyway putting a bunch of sulfur particles in the atmosphere in high latitudes didn’t really affect the energy balance of the planet very much. But again, our first initial best guess is a pretty small, maybe not negligible but a pretty small short term climate impact and even then would be only noticeable for maybe a year or less,” Brettschneider said.

Brettschneider noted that he will continue to closely track the sulfur dioxide particles in the stratosphere, which may remain in that atmospheric layer for an extended period of time. Brettschneider also said that there may be the potential for additional volcanic eruptions from Hunga Tonga, as there were prior to the major event on Friday evening.

“These volcanos tend to not just have one eruptive pulse. There’s always the biggest one and this volcano had had a couple of eruptive blasts in the previous two weeks, but it’s entirely possible — not necessarily likely that it could have several major explosive events moving forward — and so while we think this one was the biggest and in fact this was probably the biggest volcanic explosion anywhere on earth in the last 30 years, you never know if there might be another big one waiting to go off,” Brettschneider said.

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