MILLECLIM Decadal and centennial climatic variability during the last millenium in the North Atlantic and Europe

• Research unit: EU RFP
• Project number: 97.0416

Key words (English)

Climate variability; rapid climatic changes; decadal and centennial events

Alternative project number (English)

EU project number: ENV4-CT97-0659

Research programs (English)

EU-programme: 4. Frame Research Programme - 3.1 Environment

Short description (English)

See abstract

Partners and International Organizations (English)

Coordinator: CNRS Géosciences de l'Envrionnnement (F)

Abstract (English)

During the last year the installation of the two new mass spectrometers further progressed but it is still not finalised. In particular the instrument running air samples is not yet fully operational. Up to now we are only able to read 3 ion currents instead of 8 in its final set-up due to a delay of the electronic and software package which is still under development by Finnigan MAT. Nevertheless, isotope ratio results on air trapped in ice cores have revealed interesting insights into climate change. In particular the high precision measurements of nitrogen isotopes for the 8200 yr cold event and for the Dansgaard-Oeschger event 19 at around 70'000 years document for the first time significant temperature changes of 7.5°C within less than a century for the former and of 16°C within a few decades for the latter event. These very rapid climate changes are not completely understood so far.
Climate models indicate that the abrupt climate changes that we measure on various parameters in the ice cores are often associated with a collapse of North Atlantic Deep Water formation cutting off the heat transport from low latitude to northern regions and hence giving rise to a strong and abrupt cooling in the north. The last such event occurred about 8200 yrs ago and the question arises why such changes have not been observed later. We have tested a hypothesis recently put forward that there are significant oscillations on the 1500-yr time scale due to changes in the ocean's deep circulation. We could show that such a time scale is beyond the natural time scales of the ocean and that, if real, other mechanisms must be responsible for these changes.

References in databases (English)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 97.0416