BC3. Basque centre for climate change – Klima aldaketa ikergai

Seminar / Mintegia / Seminario

Lecturer:
Prof. Maria Fernanda Sanchez- Goñi.
Professor at the Ecole Pratique des Hautes Etudes, CNRS-University of Bordeaux (France)

Abstract:

Geological archives show that during the last million years, the Earth’s climate underwent repeated changes between glacial (cold) and interglacial (warm) periods approximately every 41,000 or 100,000 years, with the present-day interglacial starting 12,000 years ago. These orbitally-induced glacial-interglacial cycles were punctuated by millennial-scale climatic variability. During the last glacial period (~100,000-15,000 years ago), the amplitude of the warming events in Greenland, Dansgaard-Oeshger (D-O) events, oscillated between 6 and 16°C, and occurred in few decades. In the North Atlantic huge freshwater pulses triggered by the fragmentation of the North American ice caps, the so-called Heinrich events, lead to abrupt sea surface cooling, changes in deep water conditions and open vegetation expansion in Europe. Both D-O and Heinrich events were associated with changes in the strength of the Atlantic Meridional Overturning Circulation, rapid temperature changes in Antarctica and had a global impact as observed in the CO2 and CH4 concentration records. Since the identification of the rapid climatic variability a number of questions however remain still open such as its regional impact, the oceanic and atmospheric processes underlying this variability and how other forcing such as the orbital parameters modulate the amplitude of this variability.

Based on micropaleontological (pollen and foraminifera) and geochemical analyses of several sedimentary sequences collected in the western European margin I will show that: a) vegetation-derived atmospheric changes parallel changes in sea surface temperatures and that there is a dynamic equilibrium between vegetation and climate for short periods of forcing, b) the magnitude of the change in vegetation and climate is regionally specific and is not a simple function of the magnitude of the change in climate as registered in Greenland ice cores. Changes in the Mediterranean region below 40°N were modulated by precession while above 40°N the largest temperature increases occurred during maxima in obliquity1. At global scale, data show that northern extratropics were particularly affected by the millennial-scale variability while in the tropics vegetation records show changes corresponding to Heinrich events but the response to the D-O oscillations is less marked2. These studies have thus revealed a tight coupling between oceanic and atmospheric temperatures to rapid climate changes. However, new results show that this ocean-atmosphere coupling is not a pervasive feature throughout time, and that in the eastern North Atlantic, a contrasting situation is evident during periods of rapid ice growth leading to a glacial period when strong thermal gradients developed between a warm ocean and cold landmasses3.

1. Sánchez Goñi, M.F., Landais, A., Fletcher, W.J., Naughton F., Desprat, S., Duprat, J. (2008). Contrasting impacts of Dansgaard-Oeschger events over a western European latitudinal transect modulated by orbital parameters, Quaternary Science Reviews, 27, 1136-1151.

2. Harrison, S.P., Sánchez Goñi, M.F. (2010). Global patterns of vegetation response to millennial-scale variability and rapid climate change during the last glacial period. Quaternary Science Reviews 29, 2957-2980.

3. Sánchez-Goñi, M.F., Bard, E., Landais, A., Rossignol, L., d’Errico, F. (2013). Air-sea temperature decoupling in Western Europe during the last interglacial/glacial transition. Nature Geoscience, DOI: 10.1038/ngeo1924.

Personal webpage addresses of the lecturer:

http://www.ephe-paleoclimat.com/

http://scholar.google.fr/scholar?hl=fr&q=sanchez+goni&btnG=&lr&q=sanchez+goni&btnG=&lr=

If you are interested in attending the Seminar, please sen us an email to events@bc3research.org 

6^th May, 12:00-13:00 BC3 offices 

* The Seminar will be in English. / Mintegia ingelesez burutuko da. / El seminario se realizará en inglés.