Stretching of continents is behind an ancient global warming event, scientists say

Scientists from the University of Southampton have found that the stretching of continents has probably caused one of the most extreme and abrupt episodes of global warming in Earth’s history.

The researchers, together with colleagues from the University of Edinburgh, University of Leeds, University of Oldenburg, University of Florence and the Chinese Academy of Sciences, studied the effects global tectonic forces and volcanic eruptions during a time of extreme environmental change. 56 million years ago.

Meanwhile, a sequence of events caused the planet to warm by 5 to 8ohC, culminating with the “Paleocene-Eocene Thermal Maximum” or PETM, which lasted about 170,000 years. This caused the extinction of many deep-sea organisms, reshaping the evolutionary course of life on Earth.

The team proposes that the extensive stretching of continental plates in the northern hemisphere – much like pulling a toffee bar that thins and eventually separates – has massively reduced pressures in the deep interior of Earth. This then led to intense but short-lived melting in the mantle – a layer of sticky molten rock just below the planet’s crust. The team shows that the resulting volcanic activity coincided with, and likely caused, a massive burst of atmospheric carbon releases linked to the warming of the PETM.

The researchers’ findings should be published in the journal nature geoscience.

The high speed and magnitude of warming means that the PETM event is often considered an ancient analogue for understanding current warming, even though the mechanism is completely different.

“Despite the importance and wider relevance of PETM to global change today, the underlying cause is highly debated,” says Dr Tom Gernon, Associate Professor of Earth Sciences at the University of Southampton and lead author of the study. “It is generally accepted that a sudden and massive release of the greenhouse gas, carbon, from within the Earth must have been the cause of this event, but the magnitude and rate of warming are very difficult to explain by conventional volcanic processes.”

Using archives of rocks drilled beneath the seabed near the edge of the Atlantic Ocean, the team found critical evidence of an abrupt and widespread episode of volcanic activity in the North Atlantic Ocean that lasted just over 200,000 years, strikingly similar to the duration of the PETM.

This discovery prompted the team to investigate a larger swath of the North Atlantic region, including Greenland and the Faroe Islands. Here they found that kilometer-thick clumps of lava that began erupting just before the PETM show unusual compositions that indicate a significant increase in the amount of melting of the uppermost solid part of the Earth’s mantle. under the continent.

“This finding is significant because we know that parts of the continental mantle in this region are enriched in carbonates, a major source of carbon,” says Dr Gernon. “This rapid increase in mantle melting probably released a very large volume of carbon – certainly more than we previously expected.”

The intense volcanic activity occurred just as the landmass that united Greenland and Europe was most intensely stretched by plate tectonic forces. Eventually, North America and Greenland eventually separated from Europe, which led to the birth of the North Atlantic Ocean. Scientists believe it was this final phase of stretching that caused a substantial melting of the Earth’s mantle, leading to a massive release of carbon and, in turn, global warming.

The team used a range of different models to estimate how much carbon could have been released through this process. “Using physically realistic estimates of key features of these volcanic systems, we show that the amount of carbon needed to drive warming could have been achieved by increased melting,” says lead researcher Dr Thea Hincks at the University of Southampton and co-author. on the study.

The scientists conclude that the rapid release of gas from solid Earth plays a major role in driving abrupt warming events like the PETM, which have most likely occurred at many other times in Earth’s history. “Such rapid events cause a fundamental reorganization of the Earth’s surface environment, altering large ecosystems,” concludes Dr Gernon.