Geophysikalisches Kolloquium: Radiocarbon and Tree-rings - lessons to be learned for chronologies and paleoclimate

Radiocarbon and tree-ring dating (dendrochronology) provide well established chronometers of the past. Millennia-long tree-ring chronologies have been built in various regions of the world, the longest one, based on Central European oak and pine, now dating back to 12.600 years BP (calendar years before present, 1950 AD). The two techniques profited strongly from a close collaboration : Radiocarbon pre-dating of floating tree-ring sections facilitates chronology building, and the resulting chronologies, absolutely dated with annual accuracy, provide the back-bone for the calibration of the radiocarbon time scale.

 

Our present focus is on the extension into the Late Glacial, in a collaboration with the tree-ring laboratories in Stuttgart-Hohenheim, Zurich and Aix-en-Provence. Three floating chronologies have been built, of up to 1600 years, dating back to ca. 14.500 years BP, and separated from the absolutely dated chronology by a only a small gap of less than two centuries in the Younger Dryas.

Even while still floating, radiocarbon sequences obtained from the Late Glacial pine chronologies already provide constraints on changes water masses, and hence circulation, of the tropical Atlantic.

 

Tree-ring properties, e.g. width or late-wood density, obviously are related to climate anomalies, and at suitable locations, such as close to the limits of the habitat, temperature or precipitition has been reconstructed successfully. For the low-land sites of our multi-millennial long chronologies the climate imprint is more complex; still useful climate information, e.g. about extremes of river discharge, can be deduced.

 

High-precision radiocarbon analyses of tree-ring sections provide a unique opportunity to reconstruct solar magnetic variability over the full length of the Holocene. We observe strong synchronicity with climate proxies on multi-decadal to centennial scale, which, however, still lacks unanimously acceptance as to the mechanisms of solar forcing of climate.

Datum

05.07.2007

Uhrzeit

15:15 Uhr

Ort

Geomatikum H4
Lecture hall H4 (ground floor), University of Hamburg, Bundesstr. 55, Hamburg

ReferentIn

Bernd Kromer, Institut für Umweltphysik, Uni HD

Chair


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