In order to forecast the effect of future anthropogenic changes, it is crucial to obtain data on the natural climatic variability of the North Atlantic region and Europe. The construction of time series of climatic proxies observed in natural archives is probably the best solution to document this variability over the last few centuries (PAGES research program).
We propose to study three types of archive which provide continuous records over the last millenium with a yearly resolution: massive corals at low latitudes (Bermuda), trees from intermediate latitudes in Europe and polar ices for high latitudes (mainly Greenland and Spitzbergen).
These time series will also prove to be extremely valuable to test the predictability of climate by means of coupled ocean-atmosphere numerical models over decadal and longer time scales in the framework of the CLIVAR research program.
We shall focus our work on recently developed geochemical methods which provide quantified information on climatic and oceanographic parameters in the past:
- delta 18 O, delta 13 C, delta 14 C Sr/Ca, U/Ca, Mg/Ca, Cd/Ca measuredin the carbonate of coral skeletons as proxies of temperature, salinityand nutrients contents,
- delta D, delta 13 C and delta 18 O measured in the cellulose of trees toreconstruct temperature, humidity and possibly source region, - delta 18 O, dD and ammonium concentrations measured in polar ice toquantify temperature, air masses humidity and temperature, and regional bioactivity.
In parallel to the reconstruction of climatic time series we plan to study global climatic forcings at the same time resolution:
- solar activity: 1O Be fluxes in polar ice from Antarctica and Greenland,14 C in trees, astronomical observations during the last three centuries, - greenhouse gases concentrations: C02, CH4, N20 in polar ice from Antarcticaand Greenland,
- global volcanic activity: aerosols chemistry and frequency in polar ices.
Statistical analyses of these different time series will be used to determine the characteristic patterns and ultimately some of the causes of decadal and centennial variability in the atmosphere-ocean system. The quantification of coherency and phase between the responses of the different latitude bands will be of particular interest to study how climatic events spreads geographically over the North-Atlantic ocean and European continent.
Funding SchemeCSC - Cost-sharing contracts
91191 Gif Sur Yvette