Underwater volcanoes are normally gentle giants, but their frequent flare-ups could affect climate change, according to new research.
Triggered by short- and long-term changes in the Earth's orbit and sea levels, these volcanic flare-ups, or pulses, occur on surprisingly regular cycles in between their normal steady states - lasting anywhere from two weeks to 100,000 years.
Scientists have previously suggested that volcanoes on land play a part in climate change, even mitigating its effects due to reflecting aerosols they release into the air during an eruption. One study even says that volcanoes may be behind the infamous global warming "pause," or "hiatus." However, until now little attention has been paid to the vast ranges of volcanoes sitting beneath the ocean surface.
According to this latest study, seafloor volcanoes may help spark natural climate swings.
"People have ignored seafloor volcanoes on the idea that their influence is small - but that's because they are assumed to be in a steady state, which they're not," lead study author Maya Tolstoy, a marine geophysicist at Columbia University, said in a statement. "They respond to both very large forces, and to very small ones, and that tells us that we need to look at them much more closely."
Volcanically active mid-ocean ridges stretch across some 37,000 miles (59,500 kilometers) of the ocean floor. They are the growing edges of giant tectonic plates - as lavas push out, they form new areas of seafloor. Even when they're erupting at a fairly constant rate, undersea volcanoes spew out about eight times more lava annually than land volcanoes, and emit approximately 88 million metric tons of carbon dioxide (CO2) a year. (Scroll to read on...)
However, were these undersea volcanoes to flare up, their CO2 output would shoot up so much so that they could shift planetary temperatures, researchers suggest.
Until now observing undersea eruptions has been nearly impossible, but Tolstoy and her colleagues used sensitive new seismic instruments that allowed them to monitor 10 submarine eruption sites. They also created new high-resolution maps showing outlines of pass lava flows, spanning more than 700,000 years back.
The long-term eruption data revealed that when the Earth cooled, and sea levels dropped, pressure on volcanoes let up and eruptions surged. However, when things warmed up and sea levels rose (to levels similar to what they are today), lava erupted more slowly, creating bands of lower topography. This could be due to the weight of the ocean impacting eruptions.
According to the study, this could also be related to changes in the earth's orbit. When the orbit is more elliptical, Earth is squeezed and unsqueezed by the Sun's gravitational pull, essentially massaging undersea magma upward, researchers explain. When the orbit is circular, though, the squeezing effect is minimized and there are fewer eruptions.
"If you look at the present-day eruptions, volcanoes respond even to much smaller forces than the ones that might drive climate," Tolstoy said.
The findings, published in the journal Geophysical Research Letters, show how a surge in volcanic activity could increase the release of CO2 and impact our climate. This means that models of Earth's natural climate dynamics, and by extension human-influenced climate change, may have to be adjusted.
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