Ancient ice testifies to dozens of gigantic volcanic eruptions

(ORDO NEWS) — Ice cores drilled in Antarctica and Greenland have revealed giant volcanic eruptions during the last ice age. Sixty-nine of them were larger than any eruption in modern history.

According to the physicists at the University of Copenhagen who conducted the study, these eruptions could tell us about our planet’s sensitivity to climate change.

For many people, the mention of a volcanic eruption brings to mind doomsday scenarios involving deafening explosions, dark ash rising into the stratosphere, and fetid lava burying everything in its path as people flee in panic.

While such an eruption could theoretically happen tomorrow, we have to settle for disaster movies and books when it comes to really powerful volcanic eruptions in the modern era.

“We have not survived any of the largest volcanic eruptions in history. We are seeing it now. eruptions over the past 2,500 years,” says Associate Professor Anders Svensson from the Niels Bohr Institute at the University of Copenhagen.

By comparing ice cores drilled in Antarctica and Greenland, he and his colleagues were able to estimate the number and intensity of volcanic eruptions over the past 60,000 years. Estimates of volcanic eruptions over 2,500 years ago have so far been associated with great uncertainty and lack of precision.

Sixty-nine eruptions are larger than Tambora volcano.

Eighty-five volcanic eruptions identified by researchers were major global eruptions. Sixty-nine of these are estimated to be larger than the 1815 eruption of Mount Tambora in Indonesia – the largest volcanic eruption in recorded history.

Tambora’s eruption released so much sulfuric acid into the stratosphere that it blocked sunlight and caused global cooling in subsequent years. The eruption also caused a tsunami, drought, famine and at least 80,000 deaths.

“For the reconstruction of ancient volcanic eruptions, ice cores have several advantages over other methods. When a really large eruption occurs, sulfuric acid is released into the upper atmosphere, which then spreads around the world – including Greenland and Antarctica. We can estimate the size of the eruption, looking at the amount of precipitated sulfuric acid,” explains Anders Svensson.

In a previous study, scientists were able to synchronize ice cores from Antarctica and Greenland, i.e. date the corresponding core layers on the same time scale. Because of this, they were able to compare the sulfur residues in the ice and determine when sulfuric acid spread to both poles after globally significant eruptions.

When will it happen again?

“The new 60,000-year volcanic eruption chronology provides us with more accurate statistics than ever before. We now see that there were many more such large eruptions during the prehistoric ice age than in modern times.

Since large eruptions are relatively rare , in order to know when they occur, a long chronology is needed. That is what we have now, “says Anders Svensson.

We can only guess when the next eruption will occur. But Svensson is not prepared to make any specific predictions:

“Three eruptions of the largest known category, the so-called VEI-8 eruptions, occurred over the entire period we studied (see Facts sidebar).

So we can expect more at some point, but we just don’t we know whether it will happen in a hundred or a few thousand years.” Tamboru-sized eruptions seem to happen once or twice every thousand years, so the wait might be shorter.”

How has this affected the climate?

When volcanic eruptions are powerful enough, they can affect the global climate, where there is usually a 5-10-year cooling period. Therefore, there is great interest in mapping major eruptions of the past, as they can help us look into the future.

“Ice cores contain information about temperatures before and after eruptions, which allows us to calculate the impact on climate. Since large eruptions tell us a lot about how sensitive our planet is to changes in the climate system, they can be useful for climate prediction,” explains Anders Svensson.

Determining the sensitivity of the Earth‘s climate is the “Achilles’ heel” of modern climate models. Svensson concludes:

“Current IPCC models do not have a clear idea of ​​climate sensitivity – that is, what the effect of a doubling of CO2 in the atmosphere would be.

Volcanism can give us answers to the question of how much temperature changes when the radiation budget of the Earth’s atmosphere changes, whether due to CO2 or because of a blanket of sulfur particles. So when we evaluate the impact of large volcanic eruptions on the climate, we can use the results to improve climate models.”

DATA:

In total, the researchers identified 1,113 volcanic eruptions in Greenland ice cores and 740 eruptions in Antarctic ice cores over the past 60,000 years, where the cores contained more than 20 kg and 10 kg of sulfuric acid per square kilometer, respectively.

Eighty-five of the identified eruptions were observed by researchers at both poles of the Earth. Twenty-five of these were larger than any eruption in the past 2,500 years, and 69 were larger than Tambora’s 1815 eruption, the largest volcanic eruption recorded in the past 500 years. Their recent study is published in the journal Climate of the Past.

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