Navigation Links
When palm trees gave way to spruce trees
Date:6/17/2009

This release is available in French.

For climatologists, part of the challenge in predicting the future is figuring out exactly what happened during previous periods of global climate change.

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.

"Fossils of land plants are excellent indicators of past climates," said Dr. Greenwood. "But the fossil plant localities from the Canadian Arctic and Greenland don't appear to record this major climate change, and pose problems for precisely dating their age, so we needed to look elsewhere."

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.


'/>"/>

Contact: David Greenwood
greenwoodd@brandonu.ca
204-571-8543
Natural Sciences and Engineering Research Council
Source:Eurekalert  

Related biology news :

1. Canada provides $1.4M for removal of hazardous trees from provincial recreation sites
2. Climate change predicted to drive trees northward
3. Fighting pollution the poplar way: Trees to clean up Indiana site
4. Why juniper trees can live on less water
5. Secrets of cooperation between trees and fungi revealed
6. Ancient oak trees help reduce global warming
7. Vine invasion? UWM ecologist looks at coexistence of trees and lianas
8. Extinction most likely for rare trees in the Amazon rainforest
9. Shade trees can protect coffee crops
10. Diversity of trees in Ecuadors Amazon rainforest defies simple explanation
11. Urban trees enhance water infiltration
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
When palm trees gave way to spruce trees
(Date:3/14/2016)... 14, 2016 http://www.apimages.com ) ... --> - Renvoi : image disponible via AP ... --> --> DERMALOG, le leader ... nouveaux lecteurs d,empreintes digitales pour l,enregistrement des réfugiés ... utilisé pour produire des cartes d,identité aux réfugiés. ...
(Date:3/10/2016)... BELL, Pa. , March 10, 2016   Unisys ... U.S. Customs and Border Protection (CBP) is testing its ... San Diego to help identify certain ... States . The test, designed to help determine the ... pedestrian environment, began in February and will run until May ...
(Date:3/8/2016)... March 8, 2016   Valencell , the ... announced it has secured $11M in Series D ... a new venture fund being launched by UAE-based ... from existing investors TDF Ventures and WSJ Joshua ... continue its triple-digit growth and accelerate its pioneering ...
Breaking Biology News(10 mins):
(Date:4/27/2016)... 2016 NanoStruck Technologies Inc. ... ( Frankfurt : 8NSK) gibt bekannt, ... 13. August 2015 die Genehmigung von der CNSX ... 200.000.000 Einheiten auf 400.000.000 Einheiten zu erhöhen, um ... wurden 157.900.000 Einheiten mit dem ersten Teil der ...
(Date:4/27/2016)... ... 2016 , ... NDA Partners Chairman Carl Peck, MD ... Consultant. Mr. Clark was formerly a Vice President with US Pharmacopeia, where ... monographs based on analytical methods. NDA Partners Expert Consultants are top tier ...
(Date:4/27/2016)... ... April 27, 2016 , ... Global Stem Cells Group CEO Benito ... the founder of GSCG affiliate Kimera Labs in Miami. , In 2004, Ross received ... cell transplantation for hematologic disorders and the suppression of graft vs. host disease (GVHD) ...
(Date:4/27/2016)... , April 27, 2016 ... research report with specific focus on US, EU, ... Japan , to the healthcare business intelligence ... library. Complete report on the Flow ... companies and supported with 282 tables and figures ...
Breaking Biology Technology: