Featured Research

from universities, journals, and other organizations

Ancient Climate Change: When Palm Trees Gave Way To Spruce Trees

Date:
June 25, 2009
Source:
Natural Sciences and Engineering Research Council
Summary:
One long-standing climate puzzle relates to 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?

New research reveals the demise of an ancient forest. These are dawn redwood stumps on Axel Heiberg Island, Nunavut.
Credit: Copyright David Greenwood / Used with permission

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.

The group's detailed record of the Eocene/Oligocene transition will appear in the June 18 issue of Nature.


Story Source:

The above story is based on materials provided by Natural Sciences and Engineering Research Council. Note: Materials may be edited for content and length.


Journal Reference:

  1. James S. Eldrett, David R. Greenwood, Ian C. Harding & Matthew Huber. Increased seasonality through the Eocene to Oligocene transition in northern high latitudes. Nature, 2009; 459 (7249): 969 DOI: 10.1038/nature08069

Cite This Page:

Natural Sciences and Engineering Research Council. "Ancient Climate Change: When Palm Trees Gave Way To Spruce Trees." ScienceDaily. ScienceDaily, 25 June 2009. <www.sciencedaily.com/releases/2009/06/090617131356.htm>.
Natural Sciences and Engineering Research Council. (2009, June 25). Ancient Climate Change: When Palm Trees Gave Way To Spruce Trees. ScienceDaily. Retrieved October 20, 2014 from www.sciencedaily.com/releases/2009/06/090617131356.htm
Natural Sciences and Engineering Research Council. "Ancient Climate Change: When Palm Trees Gave Way To Spruce Trees." ScienceDaily. www.sciencedaily.com/releases/2009/06/090617131356.htm (accessed October 20, 2014).

Share This



More Earth & Climate News

Monday, October 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Powerful Hurricane Gonzalo Heads to Bermuda

Raw: Powerful Hurricane Gonzalo Heads to Bermuda

AP (Oct. 17, 2014) Hurricane Gonzalo pounded Bermuda with wind and heavy surf on Friday, bearing down on the tiny British territory as a powerful Category 3 storm that could raise coastal seas as much as 10 feet. (Oct. 17) Video provided by AP
Powered by NewsLook.com
So, Kangaroos Didn't Always Hop

So, Kangaroos Didn't Always Hop

Newsy (Oct. 16, 2014) Researchers believe an extinct kangaroo species weighed 500 pounds or more and couldn't hop. Video provided by Newsy
Powered by NewsLook.com
Hurricane Gonzalo Is A Category 4 And Heading To Bermuda

Hurricane Gonzalo Is A Category 4 And Heading To Bermuda

Newsy (Oct. 16, 2014) Powerful hurricane could hit Bermuda this weekend, and even if it misses it will likely do some damage. Video provided by Newsy
Powered by NewsLook.com
The Largest Volcano In Centuries Is Spewing Toxic Gas

The Largest Volcano In Centuries Is Spewing Toxic Gas

Newsy (Oct. 16, 2014) One of the largest volcanic eruptions in centuries is occurring on Iceland. The volcano Bardarbunga is producing high levels of sulfur dioxide. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins