The Paleocene-Eocene Thermal Maximum (PETM) remains a fascinating period in Earth’s history, marked by a significant increase in global temperatures about 56 million years ago. For years, scientists have debated the causes of this hyperthermal phenomenon, with theories ranging from the destabilization of methane hydrates to land uplift. But a groundbreaking study published in the journal Climate of the Past suggests that volcanic activity in the North Atlantic played a crucial role in driving global warming during the PETM period.
The study hypothesizes that there was a spike in volcanic activity in the North Atlantic between 56 and 54 million years ago, coinciding with the PETM period. This volcanic activity released significant amounts of greenhouse gases into the atmosphere, leading to a dramatic increase in global carbon emissions. Evidence for this is the elevated levels of lighter carbon isotopes (12C) in the shells of foraminifera, microscopic marine organisms that lived in the oceans during that period.
To investigate the link between the North Atlantic Igneous Province (NAIP) and PETM climate change, Dr. Morgan Jones and his collaborators at the University of Oslo turned to sedimentary materials on the island of Fur, Denmark. This site has a complete sediment transect covering the period before, during and after the PETM.
Scientists have analyzed hundreds of NAIP-derived ash layers found in the sediments. Studying specific elements in these layers, known as proxies, allowed them to determine volcanic activity, changes in hydrologic regimes, and weathering patterns. The presence of mercury and osmium, released during volcanic eruptions and deposited with organic matter, has served as a key indicator of NAIP activity in the pre- and post-PETM period.
The results show a progressive enrichment of these volcanic features before PETM, indicating increased NAIP activity during this period. However, a rapid decline in volcanic activity was observed during the post-PETM recovery phase. This suggests that during the PETM, NAIP underwent a transition from effusive eruptions (lava spewing) to explosive eruptions (including ash clouds and volcanic bombs).
Dr. Jones suggests that this change in volcanic activity played a critical role in the global warming observed during the PETM. The explosive eruptions released significant amounts of methane, a potent greenhouse gas, which contributed to a positive feedback in the temperature rise. Methane is known to be 28 times more efficient than carbon dioxide at trapping heat over a 100-year period.
It is estimated that up to 1,000,000 km3 of magma was erupted during this period in the North Atlantic Magma Province, which covers a vast area between Greenland, the UK and Norway. This enormous volume of magma corresponds to a carbon reservoir of about 35,000 gigatons.
The implications of this study go beyond understanding Earth’s ancient climate history. It provides valuable insights into the role of volcanic activity in global warming and points to the possible consequences of increased greenhouse gas emissions in the modern world.
Dr. Jones concluded by saying: “Studying past climate events like PETM helps us understand the complex interactions between geological processes and climate change. It serves as a stark reminder of how volcanic activity can significantly affect the Earth’s climate system.”