Vortrag 04.06.2019

Einladung zum Vortrag am 04.06.2019 um 16 Uhr ct im

Kleinen Hörsaal des Geographischen Instituts (MN 09)

 

Prof. Dr. Roland Zech

Friedrich-Schiller-Universität Jena,

Geographisches Institut, Lehrstuhl für Physische Geographie

 

Der Rhythmus der Eiszeiten:

Mit kosmogenen Nukliden, Blattwachsen und Stabilisotopen

auf der Suche nach einem heiligen Gral

 

Vortrag in englischer Sprache

The rhythm of the ice ages: looking for a holy grail using cosmogenic nuclides, leaf waxes and isotopes

 

The close correlation of atmospheric CO2 and global temperature during the ice ages reflects the important role of greenhouse gases for the climate on Earth. It is usually assumed that the deep ocean acted as sink for CO2 during glacials due to an equatorward shift of the southern westerlies, which reduced up-welling around Antarctica and ventilation of the deep ocean. However, there are a few reasons to question this current main-stream hypothesis.

(i) Surface exposure dating using cosmogenic nuclides, for example, can be used to date the past extent of the highly precipitation-sensitive glaciers in the arid southern Central Andes. Do they document a northward shift of the westerlies during the global Last Glacial Maximum at 20 ka?

(ii) Enormous amounts of carbon are stored in the organic-rich tundra soils in the permafrost region. Can leaf waxes and their isotopic composition indicate, whether permafrost soils sequestered more carbon during glacials and released carbon during interglacials?

In this talk, I will address these questions and then remember Milankovic and try to find the logic behind insolation changes, permafrost and the rhythm of the ice ages. This leads us to a “permafrost glacial hypothesis”.

 

I will then finally and very briefly present an overview over a few recent and ongoing studies in order to illustrate the great potential of cosmogenic nuclides and compound-specific isotope analyses on biomarkers for reconstructing climate and environmental changes