Featured Research

from universities, journals, and other organizations

Paradox of polar ice sheet formation solved

Date:
September 2, 2013
Source:
CNRS (Délégation Paris Michel-Ange)
Summary:
The beginning of the last glacial period was characterized in the Northern hemisphere by significant accumulation of snow at high latitudes and the formation of a huge polar ice sheet. For climatologists this was paradoxical, since snowfall is always associated with high humidity and relatively moderate temperatures. Now, scientists have solved this paradox.

The beginning of the last glacial period was characterized in the Northern hemisphere by significant accumulation of snow at high latitudes and the formation of a huge polar ice sheet. For climatologists this was paradoxical, since snowfall is always associated with high humidity and relatively moderate temperatures. Now, a French team coordinated by María-Fernanda Sánchez-Goñi, a researcher at EPHE[1] working in the 'Oceanic and Continental Environments and Paleoenvironments' Laboratory (CNRS/Universités Bordeaux 1 & 4)[2] has solved this paradox.

Related Articles


By analyzing sediment cores dating back 80,000 to 70,000 years, the researchers have shown that during that period, water temperatures in the Bay of Biscay remained relatively high, whereas those in mainland Europe gradually fell. Carried northwards by wind, the humidity released by this thermal contrast appears to have caused the snowfall that formed the polar ice sheet.

This work was published on the Nature Geoscience website on 1 September 2013.

Over the past two million years, Earth has experienced long glacial periods separated by short, warmer intervals known as interglacials. This succession of glacials and interglacials is caused by changes in insolation brought about by cyclical variations in the distance between Earth and the Sun and in the tilt and direction of our planet's rotation axis relative to the Sun. The last glacial period, which ended 12,000 years ago, began between 80,000 and 70,000 years ago. This period was marked by climate variability at the millennial time scale, with short cooling periods alternating with increasingly small improvements in the climate as glaciation set in.

Sea levels dropped by 80 meters following a reduction in insolation 70,000 years ago. This shows that there was a large accumulation of snow at high latitudes, which was the cause of the ice sheet around the North Pole. However, cold temperatures are generally associated with dry weather and scarce precipitation. For snow to fall, the weather needs to be humid and the temperature only moderately low. In these conditions, how can the accumulation of snow at the pole be explained?

To answer this question, the researchers analyzed marine sediment cores collected off Galicia (Spain) and from the Bay of Biscay, containing pollen and foraminifera, microscopic marine organisms with calcareous skeletons. Pollen grains are excellent indicators of the vegetation and temperature of the continent, while foraminifera provide information about the temperature of the ocean.

The scientists were thus able to reconstruct changes in the vegetation cover of the Atlantic seaboard and in the temperatures of the Atlantic Ocean. They observed an astonishing decoupling between the temperature of the Bay of Biscay and that of the European mainland. When temperatures were very cold on the mainland, the oceans remained warm, especially during the periods of intense cooling that took place at the onset of glaciation. The decoupling corresponds to periods when the Gulf Stream, a powerful marine current that carries the warm waters of the Gulf of Mexico northwards, was pushed towards the Bay of Biscay by the moderate iceberg break-up from the North of the American continent. It is the temperature contrast between the Bay of Biscay and the adjacent mainland that released high humidity, which was carried towards the North Pole by the winds, thus causing the heavy snowfall that formed the polar ice sheet, researchers believe.

Notes:

[1] Ecole pratique des hautes études

[2] In collaboration with the European Center for Research and Teaching in Environmental Geosciences (Aix-Marseille Université/CNRS/IRD/Collège de France), Laboratoire des Sciences du Climat et de l'Environnement (CEA/CNRS/UVSQ) and the 'De la préhistoire à l'actuel : culture, environnement et anthropologie' Laboratory (CNRS/Université Bordeaux 1/Ministère de la culture et de la communication/INRAP).


Story Source:

The above story is based on materials provided by CNRS (Délégation Paris Michel-Ange). Note: Materials may be edited for content and length.


Journal Reference:

  1. María Fernanda Sánchez Goñi, Edouard Bard, Amaelle Landais, Linda Rossignol, Francesco d’Errico. Air–sea temperature decoupling in western Europe during the last interglacial–glacial transition. Nature Geoscience, 2013; DOI: 10.1038/ngeo1924

Cite This Page:

CNRS (Délégation Paris Michel-Ange). "Paradox of polar ice sheet formation solved." ScienceDaily. ScienceDaily, 2 September 2013. <www.sciencedaily.com/releases/2013/09/130902101530.htm>.
CNRS (Délégation Paris Michel-Ange). (2013, September 2). Paradox of polar ice sheet formation solved. ScienceDaily. Retrieved November 24, 2014 from www.sciencedaily.com/releases/2013/09/130902101530.htm
CNRS (Délégation Paris Michel-Ange). "Paradox of polar ice sheet formation solved." ScienceDaily. www.sciencedaily.com/releases/2013/09/130902101530.htm (accessed November 24, 2014).

Share This


More From ScienceDaily



More Earth & Climate News

Monday, November 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Car Park Solution for Flexible Green Energy

Car Park Solution for Flexible Green Energy

Reuters - Innovations Video Online (Nov. 24, 2014) — A British solar power start-up says that by covering millions of existing car park spaces around the UK with flexible solar panels, the country's power problems could be solved. Suzannah Butcher reports. Video provided by Reuters
Powered by NewsLook.com
Ebola-Hit Sierra Leone's Late Cocoa Leaves Bitter Taste

Ebola-Hit Sierra Leone's Late Cocoa Leaves Bitter Taste

AFP (Nov. 23, 2014) — The arable district of Kenema in Sierra Leone -- at the centre of the Ebola outbreak in May -- has been under quarantine for three months as the cocoa harvest comes in. Duration: 01:32 Video provided by AFP
Powered by NewsLook.com
NY Gov. on Flood Prep: 'prepared for the Worst'

NY Gov. on Flood Prep: 'prepared for the Worst'

AP (Nov. 23, 2014) — First came the big storm. Now comes the big melt for residents of flood-prone areas around Buffalo. New York's governor says officials are preparing for the worst as the temperature is expected to rise and potentially melt several feet of snow. (Nov. 23) Video provided by AP
Powered by NewsLook.com
Anglerfish Rarely Seen In Its Habitat Will Haunt You

Anglerfish Rarely Seen In Its Habitat Will Haunt You

Newsy (Nov. 22, 2014) — For the first time Monterey Bay Aquarium recorded a video of the elusive, creepy and rarely seen anglerfish. 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