Volcanic activity and low-oxygen events in the ocean associated with global warming and rapid ice melt during the last ice age

A chemical analysis of sediment cores from the North Pacific reveals a consistent pairing of volcanic ash and hypoxia, a low-oxygen condition in the ocean spanning thousands of years, during periods of rapid climate warming at the end of the last ice age, new research published today were in Nature shows.

Understanding the relationship between volcanic activity, hypoxia, and ice melt due to warming during the last ice age, which ended about 18,000 years ago, raises important questions about what might happen if the planet warms today.

“It is currently unknown whether volcanic eruptions will increase as the climate warms,” ​​said the study’s lead author, Jianghui Du of ETH Zurich in Switzerland, who conducted the research as a doctoral student at the College of Earth, Ocean, and Oregon State University conducted atmospheric sciences.

“But we do know that the remaining glaciers on volcanoes in the Pacific Ocean’s Ring of Fire are melting rapidly, and it will be important to factor this ice loss into predictions of future eruptions that would be risky for populated regions and could also make emerging hypoxic dead zones in the North Pacific yet.” worse.”

The results suggest a systematic relationship between climate, glacial retreat, volcanic activity, biological productivity and ocean oxygen depletion, said Alan Mix, an oceanographer and paleoclimatologist at Oregon State and co-author of the study.

“These surprising connections between parts of the Earth that we normally think of as separate underscore how interconnected the whole system really is,” he said. “Solving environmental problems like the ones we face in the ongoing climate crisis requires that we look at the entire connected system with an open mind, not just individual parts.”

The volcanic region in the Pacific Ocean is known as the Ring of Fire in part because it is one of the most active tectonic and volcanic regions in the world.

The timing of volcanic events associated with the retreat of the Cordillera Ice Sheet, which once covered much of western North America, suggests that the rapid melting of ice-covering volcanoes in the region triggered increased volcanic activity, Mix said.

“The ice cover of volcanoes is like a cork in a champagne bottle. Remove the icy cork and boom, the eruptions begin,” he said.

Previous research had shown some layers of ash in sediments in the region, but Du’s chemical study, using deep-sea sediment cores from the Gulf of Alaska, revealed more traces of ash not visible to the naked eye.

You cataloged and compared volcanic eruptions in ice-covered areas with those that were not ice-covered during the last ice age.

“We found a clear pattern of many eruptions during warming and ice retreat in areas where glaciers were present, and much less change in eruption frequency outside of the ice-covered zone, particularly in western North America,” Du said. “This provides strong evidence for the volcanic response to warming and ice retreat.”

The chemical fingerprints also showed a consistent pairing of volcanic ash and hypoxic events. The increase in volcanic ash likely fueled ocean productivity, which ultimately created oxygen-poor conditions.

Texas A&M University co-authors Christina Belanger and Sharon (who uses only one name) studied a species of seafloor organisms called foraminifera and found that they closely tracked the entry of volcanic ash from the Gulf of Alaska. These organisms thrive in highly productive water bodies and can tolerate low-oxygen conditions.

“Volcanic ash contains important trace nutrients for plankton, particularly iron,” said co-author Brian Haley, a research professor at Oregon State.

“When the ash meets the ocean, the plant plankton devour this iron and thrive. This fertilizing effect underscores a practical application of our work. Some have suggested iron fertilizing the North Pacific to scavenge excess carbon dioxide from the atmosphere,” he said.

“We show that the real world has done this experiment effectively in the past with volcanic iron and the fertilization effect works and exports carbon to the deep sea. That’s good news. But there are some dangerous consequences, because as excess organic matter decomposes, it falls to the depths of the ocean, depleting oxygen and creating dead zones.”