Polar ice sheet formation : paradox solved

Monday, 2 September 2013

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 EPHE1 working in the 'Oceanic and Continental Environments and Paleoenvironments' Laboratory (CNRS/Universités Bordeaux 1 & 4)2 has solved this paradox. 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.


Left and from bottom to top: changes in atmospheric and oceanic temperatures in Western Europe and the Bay of Biscay; changes in the overall ice volume; changes in atmospheric temperature in Greenland (GI indicates periods of warming in Greenland). The blue strips represent cooling phases in the west of Europe and warming of water in the Bay of Biscay. Right: Proposed oceanic circulation model to explain the presence of warm waters in the Bay of Biscay during phases of atmospheric cooling at the onset of glaciation. The red arrows and dots show warm surface waters; blue arrows and dots show cold surface waters. NADW: North Atlantic Deep Water, SC: surface current, STG: subtropical gyre, SPG: subpolar gyre. © María-Fernanda Sánchez-Goñi

Note(s): 

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).

Source(s): 

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

Contact(s):
  • Maria-Fernanda Sanchez-Goni, Environnements et paléoenvironnements océaniques et continentaux (EPOC)
    mf [dot] sanchezgoni [at] epoc [dot] u-bordeaux1 [dot] fr, 05 40 00 83 84