The Earth Story

The PETM – Why It Feels Like Deja Vu

The Palaeocene Eocene Thermal Maximum was an event that took place 56 million years ago at the end of the Palaeocene and lasted for 150,000 – 200,000 years. The average global temperature rose by 5-9°C (9-16°F) leading to mass migrations and extinctions of flora and fauna.

The event was discovered when marine sediment cores from Antarctica showed a large and sudden excursion ( a sharp spike in the values) in carbon isotopes, indicating that a large amount of CO2 had been rapidly expelled into the atmosphere. Sounds familiar doesn’t it?

Further evidence of a large expulsion of CO2 is shown within marine sediment cores. As you can see, there is an abrupt change from white to red, indicating a rapid dissolution of calcium carbonate (white mud) that only recovers after the event (the red clay). (Increases in CO2 dissolved within seawater lead to calcium carbonate dissolving and eroded terrestrial clays (red) are deposited instead).

Today global temperatures are increasing at rate that far exceeds that of the PETM; a warming of 1°C per 100 years compared to 0.025°C in the Palaeocene.

While current global temperatures are far lower than those during the PETM it is the speed of the change that matters. All life forms take time to adapt and evolve, and it is the rapidity with which the world is warming that is threatening life as we know it. Humans are not immune to this change, and it is very likely that the current warming could lead to the next mass extinction if it is not curtailed.

Climate change is still a topic of hot debate but the most important fact to remember is this: No matter what happens the Earth will still exist and life will find a way to go on. The Earth has survived global glacials as well as global deserts and has feedback cycles that always return it to a habitable state. However, these climate shifts always incur casualties, and if there is another mass extinction, there is no guarantee that the human race will survive to tell the tale. There is no doubt that humans are expelling large volumes of CO2 into the atmosphere and therefore control over the future really does lie in our hands.

Reference: https://www.e-education.psu.edu/earth103/node/639

Further Reading: http://www.wunderground.com/climate/PETM.asp?MR=1 http://www.skepticalscience.com/co2-rising-ten-times-faster-than-petm-extinction.html http://www.geol.umd.edu/~jmerck/geol100/lectures/36b.html Image Credit: University of California Santa Cruz - Earth and Planetary Sciences

Rapid rainfall shift as seen in rocks

This photo shows an outcrop in Northeastern Spain, where 2 sedimentary units come together. The lower unit consists of fairly fine-grained sedimentary deposits, including some soils, deposited in channels flowing out of the Pyrenees Mountains. All of a sudden, about 55 million years ago, the type of sediment depositing across a wide area of northern Spain changed. It switched from fine-grained, like you see in the lower layers, to coarse-grained conglomerates like you see in the upper layer.

Poles warmed more than models expected

56 million years ago marks the boundary between the Paleocene and the Eocene Epochs. At that time, there was a rapid climate change on Earth, with extremely high temperatures at the planet’s poles, comparable to the tropics today (https://tmblr.co/Zyv2Js1vvz8m2). It is thought that at the Paleocene-Eocene boundary there was a rapid release of carbon trapped in the oceans and this triggered rapid climate change by increasing greenhouse gas abundances.

This picture shows a shell of one foraminifera, a single-celled organism that precipitates the mineral calcite from the ocean. Scientists have developed several ways to use the chemistry of this mineral as records of the temperature in the water that they formed from, specifically by measuring the abundances of the isotopes of each isotope of oxygen in the carbonate mineral.

This foram formed in the surface ocean at the North Pole during the Eocene. After it died, its shell found its way into sedimentary rocks and eventually it was measured by scientists from Yale University. They used the abundances of all 3 oxygen isotopes and the ratio of magnesium to calcium in forams like this to reconstruct the chemistry and temperature of the Eocene ocean.

They found that this foram, found at the North Pole, formed in waters that were at temperatures from 30–36°C. Not only is that vastly warmer than the nearly 0°C waters found at the North Pole today, but it is several degrees warmer than even the highest temperatures predicted by climate models for the poles at this time. Scientists base those models on the physics of the atmosphere, but they have to calibrate them based on the measurements geologists can give of what the Earth did millions of years ago.

These results imply that temperatures at the poles go up even more than predicted when there are huge spikes in atmospheric carbon dioxide, the poles are even more sensitive than scientists had previously predicted. This result, therefore, implies that the potential costs of increasing carbon dioxide in the atmosphere are even higher than scientists were predicting even last year.

-JBB

Image credit: Laura Cotton http://bit.ly/2E1etWg

Original paper: http://www.pnas.org/content/early/2018/01/12/1714744115

The Earth Story: Chapter 55.5 Ma

55.5 Ma (millions of years) ago, when India was just about to collide with Asia and Iceland had still 48 Ma to wait until emerging from the ocean, Earth went through a geologically relatively short period called the Paleocene-Eocene Thermal Maximum (PETM). As the name suggests, it's main characteristics was the rise in mean global temperature by approximately 6-8 C° in period of around 20 000 years.

I hope this sounds familiar, as an increase in temperature by ~4-6 C° in the next 100 years is exactly what we are facing right now. We have already learned that a temperature rise of such magnitude doesn't come without consequence. But what kind exactly? We are looking into a world after over 2000 x 10^9 metric tons of carbon has been added to the Earth's atmosphere. The mean sea surface temperatures have risen by 5 C° in equatorial regions and 9 C° in mid/high latitudes, bottom layers respectively by 4 to 5 C°. There are no polar ice caps.

Elevated CO2 levels have lead to excessive carbonate under-saturation in the deep ocean. The implications on calcification of marine organisms have lead to a mass extinction of benthic life forms (e.g. foraminifera). Above the sea surface, plants growing in elevated CO2 start to accumulate more carbon. This leads to cellulose-rich vegetation with higher carbon:nitrogen ratio and dropped nutritional value. With nutritionally poorer primary producer now in the food chain, what happens next? As history shows us, either of the two:

-- Consumer consumes more This was illustrated by a research conducted by Ellen D. Currano and her team, rounding up 5062 fossil leaves and inspecting the bite marks on them. Results showed an increase in average insect consumption rates during the PETM.

-- Consumer becomes smaller Yes, this is true, but it is only half of what is really going on. The relationship between different sizes of closely related species or populations has been defined by Bergmann's rule. It states that the size of the specimen is relative to both, thermoregulation and the optimization of body size, as well as the availability of food resources related to primary productivity. A research conducted by Ross Secord and his team illustrated this by looking at the evolution of the earliest horses. Let it be noted that the first species weren't bigger than a Miniature Schnauzer, but surprisingly they saw an additional decrease of ~30% in size over the first ~130,000 years, followed by a ~76% increase in the recovery phase of the PETM. This shows how cellulose-rich vegetation resulted in slower growth and reproductive rates in herbivorous mammals, conceivably resulting in preference of smaller body size.

We are probably facing a combustion of up to 4500 x 10^9 metric tons of carbon within next 300 years. This is a fast forward highway.. but to where? Changes are following our every move, environment around us moving towards a new equilibrium. Through green management and new technology we give our best to stay on top of things. As we are witnessing evolution in progress, we need to earn that top dog position or else be forgotten by the history. And we do it the most human way possible - taking as much and many with us as possible.

Just this question remains: will we be able to keep up with the changes?

-- Sarah

Image: Philip Gingerich During the PETM, some mammals adapted by temporarily shrinking. One of the earliest complete horse skeletons illustrated on the photo is from a period few million years later in the Eocene, being similar to its ancestors, only larger by 50 percent.

Reference:

http://people.earth.yale.edu/sites/default/files/lysoscience.pdf

http://www.pnas.org/content/105/6/1960.full.pdf

http://www.sciencemag.org/content/335/6071/959

The PETM – Why It Feels Like Deja Vu The Palaeocene Eocene Thermal Maximum was an event that took place 56 million years ago at the end of the Palaeocene and lasted for 150,000 – 200,000 years. The average global temperature rose by 5-9°C (9-16°F) leading to mass migrations and extinctions of flora and fauna.  The event was discovered when marine sediment cores from Antarctica showed a large and sudden excursion ( a sharp spike in the values) in carbon isotopes, indicating that a large amount of CO2 had been rapidly expelled into the atmosphere. Sounds familiar doesn’t it? Further evidence of a large expulsion of CO2 is shown within marine sediment cores. As you can see, there is an abrupt change from white to red, indicating a rapid dissolution of calcium carbonate (white mud) that only recovers after the event (the red clay). (Increases in CO2 dissolved within seawater lead to calcium carbonate dissolving and eroded terrestrial clays (red) are deposited instead). Today global temperatures are increasing at rate that far exceeds that of the PETM; a warming of 1°C per 100 years compared to 0.025°C in the Palaeocene. While current global temperatures are far lower than those during the PETM it is the speed of the change that matters. All life forms take time to adapt and evolve, and it is the rapidity with which the world is warming that is threatening life as we know it. Humans are not immune to this change, and it is very likely that the current warming could lead to the next mass extinction if it is not curtailed. Climate change is still a topic of hot debate but the most important fact to remember is this: No matter what happens the Earth will still exist and life will find a way to go on. The Earth has survived global glacials as well as global deserts and has feedback cycles that always return it to a habitable state. However, these climate shifts always incur casualties, and if there is another mass extinction, there is no guarantee that the human race will survive to tell the tale. There is no doubt that humans are expelling large volumes of CO2 into the atmosphere and therefore control over the future really does lie in our hands. - Watson Reference:  https://www.e-education.psu.edu/earth103/node/639 Further Reading:  http://www.wunderground.com/climate/PETM.asp?MR=1 http://www.skepticalscience.com/co2-rising-ten-times-faster-than-petm-extinction.html http://www.geol.umd.edu/~jmerck/geol100/lectures/36b.html Image Credit: University of California Santa Cruz - Earth and Planetary Sciences