One long-standing climate puzzle relates to a sequence of events 33.5 million years ago in the Late Eocene and Early Oligocene. Profound changes were underway. Globally, carbon dioxide levels were falling and the hothouse warmth of the dinosaur age and Eocene Period was waning. In Antarctica, ice sheets had formed and covered much of the southern polar continent.
But what exactly was happening on land, in northern latitudes? When and how did Northern glaciation begin, and what does this knowledge add to the understanding of the relationship between carbon dioxide levels and today's climate?An international team that included Dr. David Greenwood, an NSERC-funded researcher at Brandon University, now provides some of the very first detailed answers, and they come from an unusual source.
The "where" was in marine sediments entombed when the North Atlantic Ocean was beginning to open, and lying now at the bottom of today's Norwegian-Greenland Sea. Sediment cores taken from there contained a record of ancient spores and pollen blown from the continent to the west.
"These marine sediment cores give us a very precise chronology of the changes in the dominant land plants," said Dr. Greenwood "and since many of these species have modern relatives, we can assume that the temperatures and environments they lived in were very similar."
To arrive at a holistic picture of the climate of the transition, the researchers merged the plant data with physical information about the state of the atmosphere and ocean taken from chemical and isotopic information in the same sediments, and compared this to computer modelling of climate in the period.
"We can see that summer temperatures on land remained relatively warm throughout the Eocene/Oligocene transition, but that the period was marked by increasing seasonality," said Dr. Greenwood.
"Mean temperatures during the coldest month dropped by five degrees Celsius, to just above freezing," he said.
"This was probably not enough to create much in the way of continental ice on East Greenland," he said, "but it did wipe out palms and other subtropical trees such as swamp cypress. They were replaced by temperate climate trees such as spruces and hemlock."
The researcher said that, nonetheless, the middle period of the transition remained fairly warm. "Hickory and walnut were still present, but these became rare in the final stages," he said.
Although the march to a cooler world was gradual in northern latitudes, it was inevitable according to Dr. Greenwood.
"Changes in the earth's position in its orbit were leading a much greater seasonal range in radiation for polar regions and, overall, heat was becoming more concentrated in the tropics, largely due to a global drop in carbon dioxide levels in the atmosphere" he said.
The group's detailed record of the Eocene/Oligocene transition will appear in the June 18 issue of Nature. Further information can be found in a release from the University of Southhampton, England.
David Greenwood | EurekAlert!
Upcycling 'fast fashion' to reduce waste and pollution
03.04.2017 | American Chemical Society
Litter is present throughout the world’s oceans: 1,220 species affected
27.03.2017 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
27.04.2017 | Life Sciences
27.04.2017 | Physics and Astronomy
27.04.2017 | Earth Sciences