Geneva: The Paleocene-Eocene Thermal Maximum (PETM), which resembles current and future warming, occurred 56 million years ago and was one of the largest and fastest global warming events in Earth’s history. Global temperatures increased by 5-8°C during this phase. It was characterised by a rise in the seasonality of rainfalls, which caused a considerable amount of clay to be transported into the ocean and rendered unsuitable for several types of living organisms. This situation might happen again right now.
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The Paleocene-Eocene Thermal Maximum (PETM), which occurred 56 million years ago, is the largest and most rapid climatic disturbance of the Cenozoic era (65.5 million years ago to the present day). Exceptional both in terms of its amplitude (5-8°C increase) and its suddenness (5,000 years, a very short time on a geological scale), this episode was marked by a warming of temperatures on a global scale. It lasted for about 200 000 years and led to numerous marine and terrestrial extinctions.
It would have been caused by a high concentration of carbon dioxide — the famous CO2 — and methane in the atmosphere, two powerful greenhouse gases. As is the case currently, these gases may have been released by several phenomena, certainly in combination: the release of methane hydrates trapped on the seabed, the sudden and significant melting of the permafrost, and the injection of magma into the organic sediments of the western edge of Norway. The origin of these processes is still under debate. The impact of a meteorite and/or the effects of intense volcanic activity in the depths of the North Atlantic could be responsible.
Because of the many similarities between PETM and current warming, the geological remains of this period are being closely studied by scientists. A team from the UNIGE is now reporting new elements.
‘The objective of our study was to investigate the influence of these climatic changes on sedimentary systems, i.e. on the processes of sediment formation and deposition, and to understand how these changes could have been transmitted from the atmosphere to the depths of the ocean,’ explains Lucas Vimpere, a post-doctoral scholar at the Section of Earth and Environmental Sciences of the UNIGE’s Faculty of Science and first author of the study.
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The researchers analysed sediments taken from more than 8km deep in the Gulf of Mexico. This basin acts as a giant ”sink” into which material eroded and transported from the North American continent over millions of years is discharged. “For reasons of cost and infrastructure, the sediments used to study the PETM are generally taken from shallow marine or continental environments.
Thanks to the collaboration of an oil company, we were able to obtain a sample of unprecedented quality, without any alteration,” said the researcher. The 543-metre-long core contains a 180-metre-thick PETM sedimentary record, making it the most complete geological ‘archive’ of this period in the world.
The UNIGE scientists found that it was composed first of a large layer of clay and then of a layer of sand, a counter-intuitive result.
At the time of the PETM, we thought that there had been more precipitation, and therefore more erosion, and that large quantities of sand had then been transported first by the fluvial systems into the oceans. However, thanks to our sample, we were able to determine that it was the clays and not the sands that were transported in the first instance, said Sebastien Castelltort, full professor at the Earth and Environmental Sciences Section of the UNIGE Faculty of Science, and last author of the study.
This established that the period was not marked by an increase in the annual rate of precipitation but by an increase in its seasonality and intensity.
This resulted in increased mobility of the river channels — the deepest areas of a river — which in turn transported large quantities of fluvial clays deposited on the adjacent alluvial plains to the ocean depths. We can now consider the presence of clay in deep basins as a marker of increased rainfall seasonality. The PETM is a potential analogue of current warming. As recent IPCC reports show, we are also now seeing an increase in the seasonality and intensity of rainfall. As our study shows, this is likely to destabilise sedimentary systems in the same way as during the PETM and with the same consequences for the oceans and living species, said Lucas Vimpere. The phenomenon has led to an increase in ocean turbidity that is harmful to marine life, especially corals.
These new data can now be integrated into modelling aimed at predicting the evolution and consequences of global warming.
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(This story has not been edited by NDTV staff and is published from a syndicated feed.)
NDTV – Dettol have been working towards a clean and healthy India since 2014 via the Banega Swachh India initiative, which is helmed by Campaign Ambassador Amitabh Bachchan. The campaign aims to highlight the inter-dependency of humans and the environment, and of humans on one another with the focus on One Health, One Planet, One Future – Leaving No One Behind. It stresses on the need to take care of, and consider, everyone’s health in India – especially vulnerable communities – the LGBTQ population, indigenous people, India’s different tribes, ethnic and linguistic minorities, people with disabilities, migrants, geographically remote populations, gender and sexual minorities. In wake of the current COVID-19 pandemic, the need for WASH (Water, Sanitation and Hygiene) is reaffirmed as handwashing is one of the ways to prevent Coronavirus infection and other diseases. The campaign will continue to raise awareness on the same along with focussing on the importance of nutrition and healthcare for women and children, fight malnutrition, mental wellbeing, self care, science and health, adolescent health & gender awareness. Along with the health of people, the campaign has realised the need to also take care of the health of the eco-system. Our environment is fragile due to human activity, which is not only over-exploiting available resources, but also generating immense pollution as a result of using and extracting those resources. The imbalance has also led to immense biodiversity loss that has caused one of the biggest threats to human survival – climate change. It has now been described as a “code red for humanity.” The campaign will continue to cover issues like air pollution, waste management, plastic ban, manual scavenging and sanitation workers and menstrual hygiene. Banega Swasth India will also be taking forward the dream of Swasth Bharat, the campaign feels that only a Swachh or clean India where toilets are used and open defecation free (ODF) status achieved as part of the Swachh Bharat Abhiyan launched by Prime Minister Narendra Modi in 2014, can eradicate diseases like diahorrea and the country can become a Swasth or healthy India.
