Sub-annual cyclicity in modern and paleoclimate archives: Resolving seasonality influence on ancient and modern climate. (IWT700)

The study of paleoclimatology has revealed the nature of fundamental mechanisms driving Earth’s climate through geologic history. Such mechanisms include large scale forcing mechanisms that control climate over a wide range of timescales. The response of various climate parameters through time is measured using geochemical proxies like (stable) isotope ratios, (trace) element abundances and other properties of sedimentary rocks. The incorporation of these proxies in sedimentary rocks is related to the state of various environmental parameters. Climate can be reconstructed using geochemical proxy records, which reveal evolution of climate through time. Climate models can be calibrated using this paleoclimatology data. These models can then be used to predict weather and climate in the future. By far most of the paleoclimatological research has focused on climate fluctuations at the time resolution of orbital (Milankovitch) cycles, like climatic precession (~21 kyr), obliquity (~41 kyr) and eccentricity (~100 kyr), and lower frequency cycles, up to tectonic scale (>1 Gyr). Recently, the reconstruction of climate variation at higher resolution (sub-Milankovitch to sub- annual scale) has received more attention. Such research is of great importance for understanding Earth’s climate on the scale of a human lifespan, and is of particular interest in the anthropogenic climate change debate. Research of seasonal variation in climate proxies yields important data, constraining the uncertainties in long-term climate reconstructions and placing them in the context of short timescale variations. The importance of studying climate on these short timescales is illustrated by the fact that the variation in climate parameters measured through one single year is higher than the reconstructed variation in these parameters over the last 5 million year. This makes the seasonality cycle the most important cycle in climate fluctuation. Most sub-annual scale research focuses on the Quarternary time period. However, sub- annual scale proxy records from deep-time settings are essential for understanding Earth’s climate during times of non-icehouse climate, because these settings provide a better analog for future greenhouse climate. This study evaluates the use of multi-proxy records derived from different types of sedimentary deposits for reconstructing seasonal variations in climate parameters. Both Quarternary and deep-time records of sub-annual variation are studied and compared to records that provide a modern analogue. This way, the relationship between the proxy records and actual climate can be studied, and the success of using the proxy records for seasonal climate reconstruction can be evaluated.The project will reveal new methods to study seasonal variations in paleo-environment as well as evaluate the success of using more well-studied proxy records in doing so. Besides evaluating methods of sub-annual climate reconstruction, the results of the project will add to our understanding of the climate system, help improve climate models by providing new ground- truth data to calibrate them, and form a basis for the interpretation of other (high-resolution) climate records.

Keywords:Cyclicity, Seasonality, Paleoclimate, Speleothem, stable isotope geochemistry

Disciplines:Climatology